Co-reporter:Qiao Zhang, Hongmei Deng, Leilei Chen, Lu Yu, Jiahua Tao, Lin Sun, Pingxiong Yang, Junhao Chu
Journal of Alloys and Compounds 2017 Volume 695() pp:482-488
Publication Date(Web):25 February 2017
DOI:10.1016/j.jallcom.2016.11.121
•Cu2CdxZn1−xSnS4 (CCZTS) thin films have been prepared by direct liquid coating (DLC) technique.•XRD and Raman demonstrate the structural transition from kesterite to stannite with increasing Cd content.•The incorporation of Cd in Cu2ZnSnS4 (CZTS) contributes to formation of notable large grains.•The band gap energy of CCZTS thin films can be tuned almost linearly between 1.35 and 1.15 eV varying with Cd compositions.Cu2CdxZn1−xSnS4 (CCZTS) thin films with varying the degree of cation substitution were fabricated employing a facile procedure by spin-coating the precursor solutions followed by post-sulfurized treatment. Combining the results from X-ray diffraction and Raman spectroscopy, the substitution of Zn with Cd was confirmed as well as a phase transition from kesterite to stannite with the increase of Cd content in CCZTS. The progressive cation substitution was demonstrated by the red shift in XRD patterns along with the Raman peaks move towards lower wavenumber, and the increasing calculated unit cell, which indicates the lattice expansion. It is observed that the grain size was dramatically improved with the incorporation of Cd into Cu2ZnSnS4 (CZTS) films. In particular, the band gaps of the CCZTS films determined by optical transmittance spectra were presented to be controlled linearly by adjusting the Cd/(Cd + Zn) ratios of the synthesis precursors from 1.35 (x = 0.0) to 1.15 eV (x = 1.0) with a small bowing constant of the bowing model (0.10 eV). The knowledge gained about the kesterite-stannite transition in CCZTS allowed fundamental understanding of alloying Cd into CZTS of pre-annealed and post-sulfurized consequently for high crystallinity. This further leads to awareness about practical possibility of cation substitution induced grain growth, phase transition in CCZTS, and suggests that such treatments are potential to develop efficient band gap engineering of these compounds towards the fabrication of Cu-based solar cells.
Co-reporter:Benlong Guo, Hongmei Deng, Xuezhen Zhai, Wenliang Zhou, Xiankuan Meng, Guoen Weng, Shaoqiang Chen, Pingxiong Yang, Junhao Chu
Materials Letters 2017 Volume 186() pp:198-201
Publication Date(Web):1 January 2017
DOI:10.1016/j.matlet.2016.09.094
•BiFe1−xCrxO3 thin films were deposited on quartz substrates by sol-gel.•The BiFe1−xCrxO3 thin films underwent a visible structural transformation.•The optical properties of BiFe1−xCrxO3 films were first studied by PL spectra.•The magnetic properties of BiFe1−xCrxO3 films were significantly enhanced.BiFe1−xCrxO3 (xBFCO, x=0, 0.03, 0.06 and 0.09) polycrystalline films have been prepared on quartz substrates by a sol–gel technique. X-ray diffraction clearly reveals the crystal structure of xBFCO thin films transforms from rhombohedral to orthorhombic, moreover, inter planar spacing and grain size of xBFCO are reduced slightly. Scanning electron microscopy shows that Cr doping can improve surface morphology and reduces the average grain size of the films. The photoluminescence (PL) spectra of xBFCO thin films at room temperature show a strong emission in the blue region. With increasing x from 0.00 to 0.09, the band gap (Eg) of xBFCO films decreases and can be expressed by Eg=(2.58−0.67x) eV. Compared with BiFeO3 film, the saturation magnetization of xBFCO (x=0.03, 0.06 and 0.09) films is significantly enhanced, which provides potential applications in information storage.
Co-reporter:Xiankuan Meng, Hongmei Deng, Qiao Zhang, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2017 Volume 186() pp:138-141
Publication Date(Web):1 January 2017
DOI:10.1016/j.matlet.2016.10.002
•The growth mechanism of CFTS has been investigated.•The grain growth of CFTS can be divided into three stages.•Vibrational mode of CFS-A1 has been calculated as 273 cm−1.Cu2FeSnS4 (CFTS) thin films have been prepared on glass substrates by a process of sputtering metallic precursor with post-sulfurization. By means of various holding times, the growth mechanism of CFTS has been determined by X-ray diffraction and Raman patterns. Three steps have been involved, the binary-phases CuSx, FeSx and SnSx are synthesized in the preliminary stage, and afterwards, CuSx reacts with FeSx to generate ternary-compound CuFeS2. At last, the target product CFTS is obtained with the increasing holding time of sulfurization. All the thin films have smooth and closely packed surface, and longer holding time is in favor of the grain growth. The thickness of these thin films is around 1 µm.
Co-reporter:Tiantian Wang, Hongmei Deng, Wenliang Zhou, Xiankuan Meng, ... Junhao Chu
Ceramics International 2017 Volume 43, Issue 8(Volume 43, Issue 8) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.ceramint.2017.02.060
Perovskite compounds of the formula (1-x)BiTi3/8Fe2/8Mg3/8O3–xCaTiO3 ((1-x)BMFT-xCTO), a class of highly potential ferroelectric photovoltaic materials with a morphotropic phase boundary (MPB), have been synthesized by solid-state reaction and exhibit simultaneously visible-light response and ferromagnetic order at room-temperature (RT). The effects of structural phases and lattice distortions on electron transitions and orbital orderings are systematically investigated. The crystal lattice displays constriction with increasing x and Raman peaks show non-liner shift due to Bi3+ and Fe3+/Mg2+ replaced by Ca2+ and Ti4+ randomly, respectively. Microstructural characterizations illustrate the rhombohedral-orthorhombic MPB occurrence during the crystal growth. Optical spectroscopy analysis shows band-gaps of our samples are about 2.2 eV with anomalies at the point of phase transition. Furthermore, the (1-x)BMFT-xCTO displays RT ferromagnetism when x<0.15, which can be explained by an F center theory. These results reveal rich physical phenomena and open an avenue to design promising perovskites for solar-energy conversion devices and multiferroic applications.
Co-reporter:Lu Yu, Hongmei Deng, Wenliang Zhou, Pingxiong Yang, Junhao Chu
Ceramics International 2017 Volume 43, Issue 8(Volume 43, Issue 8) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.ceramint.2017.02.014
The xBi(Zn1/2Ti1/2)O3-BaTiO3 (xBZT-BT) ceramics, where x (mol) =0, 0.03, 0.06, 0.09, and 0.12, have been prepared by a solid-state reaction method. The phase transition, microstructure and optical properties were investigated. X-ray diffraction patterns indicate that the as-prepared samples have a polycrystalline perovskite structure. For x<0.06, the xBZT-BT ceramics exhibit clear tetragonal symmetry, and transform to rhombohedral phase as 0.06< x≤0.12. Coexistence of both tetragonal phase and rhombohedral phase is observed for x=0.06. The lattice strain is estimated by the Williamson-Hall analysis model, which suggests that the incorporation of substitution ions into the host lattice produces the inner stress field gives rise to structure distortions. The Raman scattering spectra corroborate the decrease in tetragonality with increasing the x, where the characteristic variation of phonon modes indirectly reveal the incorporation of Bi(Zn1/2Ti1/2)O3. Furthermore, the optical band gaps of xBZT-BT ceramics show a non-linear change, which can be explained by the crystal field theory and phase structure effect.
Co-reporter:Leilei Chen, Hongmei Deng, Qiao Zhang, Jiejin Yu, Jiahua Tao, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2017 Volume 206(Volume 206) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.matlet.2017.07.041
•Cu2MnSn(S,Se)4 (CMTSSe) thin films have been fabricated by sol-gel technique.•The properties of CMTSSe films depend strongly on the selenization temperature.•Single-phase CMTSSe films were formed in the temperature range of 500–540 °C.•The optimized CMTSSe device shows the highest open circuit voltage of 444 mV.Cu2MnSn(S,Se)4 (CMTSSe) thin films were fabricated by using spin-coating and following selenized for different temperature. Single-phase CMTSSe films have been formed in the temperature range of 500–540 °C. Both XRD patterns and Raman measurements reveal that the selenization temperature drives the films exhibited high crystallinity and strong preferred orientation in the (1 1 2) plane. The excessive elevated selenization temperature during the grain growth would lead to the decomposition of CMTSSe phase and severe Sn loss. Further morphological studies indicate an abrupt transition from a smooth and dense microstructure to a roughness structure with many voids. The band gap energy of the CMTSSe films varied from 1.43 to 1.52 eV relying on the element loss during selenization. The solar cell device with the CMTSSe layer selenized at 540 °C achieved the highest open circuit voltage of 444 mV.
Co-reporter:Tiantian Wang, Hongmei Deng, Huiyi Cao, Wenliang Zhou, Guoen Weng, Shaoqiang Chen, Pingxiong Yang, Junhao Chu
Materials Letters 2017 Volume 199(Volume 199) pp:
Publication Date(Web):15 July 2017
DOI:10.1016/j.matlet.2017.04.068
•Slightly Mn and Mg co-doped BiFeO3 films grown on Si (1 0 0) substrates are synthesized by sol-gel technique.•The improved surface morphology and decreased grain size of films due to Mn and Mg ions doping are observed.•The bandgap of xBFMMO films calculated through Photoluminescence spectra expresses non-liner variation.•The origin of ferromagnetism in xBFMMO films is discussed.Slightly Mn and Mg co-doped BiFeO3 films (BiFeO3, BiFe0.95Mg0.01Mn0.04O3, BiFe0.94Mg0.02Mn0.04O3 and BiFe0.93Mg0.03Mn0.04O3, xBFMMO, x = 0, 0.01, 0.02 and 0.03) have been grown on Si (1 0 0) substrates by sol-gel technique. Rhombohedral lattice structure and phase transition is confirmed by X-ray diffraction and Raman spectroscopy. The improved surface morphology and decreased grain size of films can be observed in SEM micrographs due to the influence of Mn and Mg co-doping. Blue emissions of xBFMMO films can be found in Photoluminescence spectra, meanwhile the nonlinear shift of emission peaks imply the variation of bandgap. Room-temperature magnetization versus magnetic field (M-H) curves exhibit enhanced saturation magnetization compared with parental BiFeO3, which can attribute to destroyed spin cycloid and released locked magnetization. These properties offer a great potential on the multiferroic information storage application.
Co-reporter:Tiantian Wang, Hongmei Deng, Xiankuan Meng, Huiyi Cao, ... Junhao Chu
Ceramics International 2017 Volume 43, Issue 12(Volume 43, Issue 12) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.ceramint.2017.04.010
Aurivillius compound Bi6Fe2-xCox/2Nix/2Ti3O18 (xBFCNT, 0≤x≤1) ceramics synthesized by a conventional solid state method, can exhibit simultaneously visible-light response, ferroelectric and ferromagnetic orders at room-temperature. The effects of structural phases and lattice distortions on electron transitions, polarizations and orbital orderings have been systematically investigated. Narrow band gaps of xBFCNT were confirmed and modified from 2.12 eV to 1.28 eV with increasing x by ultraviolet-visible-near infrared spectrophotometer. Co and Ni ions co-doping is found to induce ferromagnetic behavior but affects adversely the ferroelectric characteristics. In particular, the x=0.4 composition show obvious ferromagnetism with maximum remnant magnetization Mr (0.5 emu/g) and saturation magnetization Ms (2.4872 emu/g), due to spin canting of Fe/Ni/Co-based sub-lattices. These results reveal rich physical phenomena and open an avenue to design promising solar-energy conversion devices and multiferroic applications.
Co-reporter:Tiantian Wang;Hongmei Deng;Wenliang Zhou
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 1) pp:934-938
Publication Date(Web):26 August 2016
DOI:10.1007/s10854-016-5610-2
Bi(Mg3/8Fe2/8Ti3/8)O3 (BMFT) perovskite oxide ceramic has been synthesized by a conventional solid-state reaction method at ambient pressure. Structural characterization is detected by X-ray diffraction (XRD) and Raman spectroscopy, reflecting a polycrystalline perovskite structure. The peaks in XRD pattern shift toward lower angle, which indicates larger lattice constant than BiFeO3 (BFO). High frequency modes blue shift and the peak broadening can be observed clearly in micro-Raman spectroscopy compared with BFO patterns. Morphology analysis through scanning tunneling microscope shows dense and well-interlinked grains. Through the UV–Vis–NIR spectra, BMFT displays a narrow band gap of 2.23 eV, smaller than the 2.8 eV band gap of BFO. The room-temperature ferromagnetism of BMFT ceramic is measured for the first time, which can be attributed to the nonmagnetic ions of Mg2+ and Ti4+ ions replacing Fe3+ ions that causing the remanent magnetic moments. These results will open an avenue to further design multiferroic data storage and photovoltaic devices.
Co-reporter:Leilei Chen, Hongmei Deng, Jiahua Tao, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2017 Volume 201(Volume 201) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.matlet.2017.05.025
•Cu2MnSn(S,Se)4 (CMTSSe) thin films have been firstly prepared by sol-gel method.•The properties of CMTSSe thin films depend strongly on the post-selenization time.•Longer selenization time would leading to the overgrowth of the CMTSSe thin films.•The band gap of CMTSSe thin films decreases with increasing the selenization time.Cu2MnSn(S,Se)4 (CMTSSe) thin films were synthesized by using spin-coating technique and the structure, composition and optical properties have been investigated. XRD patterns and Raman measurements reveal that the crystallinity of the films is significantly dependent on the selenization time. The grain size of the CMTSSe thin films is demonstrated to be improved and the surface comes to compact without any visible cracks and voids with increasing time. Notably, the longer selenization time (>20 min) would lead to the overgrowth of the films and decomposition of the CMTSSe phase. Especially the escape of Sn and S/Se elements in the form of SnS(e) would resulting in a rough surface with few pin holes. The band gap of all these films are between 1.4 and 1.7 eV. The solar cell device with the CMTSSe layer selenized for 20 min achieves the highest open circuit voltage of 338 mV.
Co-reporter:Lu Yu, Hongmei Deng, Wenliang Zhou, Pingxiong Yang, Junhao Chu
Materials Letters 2017 Volume 202(Volume 202) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.matlet.2017.05.077
•A new type of perovskite KBNFO are synthesized by solid-state reaction method.•A sequence of phase transitions are observed in the KBNFO ceramics.•The band gap of xKBNFO is low and shows tunable depending on the composition.•The KBNFO materials present room-temperature ferromagnetism.The phase transition, microstructure, optical and magnetic properties of a novel material (1−x)KNbO3−xBaNb1/2Fe1/2O3 (xKBNFO) have been investigated. X-ray diffraction and Raman scattering spectra analyses suggest that all the samples are polycrystalline perovskite structure with an obvious phase transition. Optical absorption spectra indicate that BaNb1/2Fe1/2O3 (BNFO) doping has an effect on the energy band structure. The KBNFO ceramics exhibit the band gap (Eg) in the range of 1.72–2.48 eV, much smaller than the 3.25 eV Eg of KNbO3 material. Furthermore, the KBNFO materials present room-temperature ferromagnetism, and the magnetism can be controlled by the BNFO doping content. These results are helpful in the deeper understanding of phase transition, band gap tunability, and magnetism variations in perovskite and show the potential roles in perovskite solar cells and multiferroic applications.
Co-reporter:Tiantian Wang, Hongmei Deng, Peng Shen, Jin Hong, Fangyu Yue, Liangqing Zhu, Pingxiong Yang, Junhao Chu
Materials Letters 2017 Volume 204(Volume 204) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.matlet.2017.06.024
•Monocrystalline Bi2Fe4O9 film is deposited on SrTiO3 by PLD for the first time.•Well-organized surface of Bi2Fe4O9 film is measured by SEM and AFM.•Ferromagnetism has been detected in Bi2Fe4O9 thin film by M-H hysteresis curve.•The band gap of thin film is calculated as 1.5 eV through transmission spectrum.Mullite Bi2Fe4O9 single crystal epitaxial thin film has been successfully synthesized on SrTiO3 (1 0 0) substrate by pulsed laser deposition. The single crystal thin film is grown along (m 0 0) orientation (m = 2, 4) which is identified by X-ray diffraction. Morphology analysis shows orderly assigned grains with some small defects due to the volatilization of Bi2O3 tested by scanning electron microscope and atomic force microscopy. The chemical composition of film is confirmed by energy dispersive X-ray spectroscopy, nearly in accord with the chemical formula. M-H hysteresis curve confirms the ferromagnetism in single crystal thin film which can be attributed to canted non-collinear anti-ferromagnetic spin order caused by structural distortion. The band gap of thin film is calculated as 1.5 eV through transmission spectrum which is very suitable for solar cell. This research not only lay a solid foundation on further researching Bi2Fe4O9 single crystal epitaxial film, but also open an avenue to design various multifunctional devices.
Co-reporter:Leilei Chen, Hongmei Deng, Jiahua Tao, Huiyi Cao, Lin Sun, Pingxiong Yang, Junhao Chu
Acta Materialia 2016 Volume 109() pp:1-7
Publication Date(Web):1 May 2016
DOI:10.1016/j.actamat.2016.02.057
Abstract
The synthesis approach using a non-toxic solution-based method accompanied with special post-annealing processes demonstrates the great potential to realize industrial manufacture of earth-abundant materials for sustainable photovoltaics. Exploration of an appropriate post-annealing process is significant to gain insight into the crystallization of solar materials. The earth-abundant Cu2MnSnS4 (CMTS) thin films were fabricated by post-sulfuring as-prepared precursors and the results have been compared with that of directed-annealed samples. It was found that the sulfurization procedure not only can support to enhance the crystallinity but also help to obtain a nearly stoichiometric CMTS thin film which also free of SnS secondary phase. This reaction also contributes to sustainable incorporation of S into CMTS to a considerable extent and formation of notable large grains; whereas, it leads to the formation of a typical bi-layer microstructure containing large grains (500–800 nm) on the top and fine grains at the bottom. Through the sulfurization approach, the device performance is improved with the power conversion efficiency shows a 170% increase which mainly via the boost of open circuit and fill factor compared with that of direct-annealed processed. These results offers a novel research direction for preparing pure-sulfide CMTS thin film for the potential application in low-cost solar cells.
Co-reporter:Huiyi Cao, Hongmei Deng, Leilei Chen, Jiahua Tao, Xiankuan Meng, Jian Liu, Fangyu Yue, Lin Sun, Pingxiong Yang, Junhao Chu
Journal of Alloys and Compounds 2016 Volume 689() pp:21-29
Publication Date(Web):25 December 2016
DOI:10.1016/j.jallcom.2016.07.323
•The Sb-doping content dependence of the properties of CIAS films has been studied.•The phase-pure Sb-doped CIAS films with a decreased defects can be obtained.•Significant Sb-induced grain size increase and smooth surface has been observed.•The Sb-doped device demonstrates two-orders of magnitude in current amplification.The influence of antimony (Sb) doping content on the structural properties of Cu(In, Al)Se2 (CIAS) thin films and performance of photodetector has been investigated systematically. Here, we report the high-quality, phase-pure and well-crystallized CIAS thin films containing Sb element, where the lattice defects can be restrained effectively. Moreover, significant Sb-induced grain size enhancement, dense and smooth surface morphology can be observed, which originates from that the low melting point Sb-based compounds play as fluxing agents during the grain growth process. Most importantly, after Sb doping, the photodetector with the Al:ZnO (AZO)/CIAS/Mo structure demonstrates a two-orders of magnitude in photocurrent amplification, which indicates the reduced recombination of charge carriers in the depletion region. These findings provide additional insight into their use for the forthcoming photodetector application.
Co-reporter:Wenliang Zhou, Hongmei Deng, Pingxiong Yang, Junhao Chu
Ceramics International 2016 Volume 42(Issue 15) pp:17162-17167
Publication Date(Web):15 November 2016
DOI:10.1016/j.ceramint.2016.08.004
Abstract
The PbTi1−xPdxO3−δ (xPTPO) thin films prepared by chemical solution deposition have been investigated by means of structural characterizations, optical and magnetic measurements. X-ray diffraction patterns show that all the films have a pseudotetragonal perovskite structure, but also exhibit a lattice dilatation behavior and increased internal strain as the x increases. A possible mechanism for strain-induced structural evolution is discussed. Raman scattering further corroborates this change in average structure, where the characteristic variation of phonon modes, indirectly reveal the incorporation of Pd2+ ions into host lattice. Transmittance spectra analysis indicates that Pd doping has a key effect on the energy band structure. The optical bandgap of xPTPO films decreases significantly with increasing Pd content, expressed by (3.5–9.0x) eV (0≤x≤0.09). Also, magnetic switching driven by doping has been confirmed in the films, which is attributed to the competition between ferromagnetic and paramagnetic/antiferromagnetic components.
Co-reporter:Tuo Zheng, Hongmei Deng, Wenliang Zhou, Xuezhen Zhai, Huiyi Cao, Lu Yu, Pingxiong Yang, Junhao Chu
Ceramics International 2016 Volume 42(Issue 5) pp:6033-6038
Publication Date(Web):April 2016
DOI:10.1016/j.ceramint.2015.12.157
Transition metal (TM=Fe, Ni and Mn) ions doped PbTiO3 perovskite ferroelectric ceramics prepared by a solid state reaction method have been studied by means of structural characterizations, optical and magnetic measurements. All the samples have pure tetragonal perovskite structure, but exhibit different grain shapes and sizes with the introduction of TM ions and oxygen vacancies. The observed structural changes arise from internal lattice strain, which is estimated by Williamson–Hall (W–H) analysis model. Moreover, TM ions doping plays simultaneously an important role on the energy band structure and magnetic orderings. The energy gap of PbTi0.95TM0.05O3−δ shows a drastic decrease compared to that of PbTiO3. Furthermore, PbTi0.95TM0.05O3-δ materials possess multiple magnetism switching, in which diamagnetic–ferromagnetic transition and ferromagnetic–paramagnetic transition occur. In particular, the Fe-doped PbTiO3 ceramic presents a typical ferromagnetic hysteresis, originating from the effective exchange coupling interaction between oxygen vacancies and Fe 3d spins.
Co-reporter:Yingbin Zhang, Jiahua Tao, Yifeng Chen, Zhen Xiong, Ming Zhong, Zhiqiang Feng, Pingxiong Yang and Junhao Chu
RSC Advances 2016 vol. 6(Issue 63) pp:58046-58054
Publication Date(Web):13 Jun 2016
DOI:10.1039/C6RA05765A
The optimization processes for the mass-production of high-efficiency multi-crystalline silicon solar cells have been observed in this paper. After incorporating several practical advanced technologies such as grain-size controlled low defect-density mc-Si casting ingot, precisely aligned selective emitter, surface-damage free reactive ion etch texturing on a mass production line, the total-area efficiencies up to 18.84% and a production average efficiency of 18.65% for large size (156 × 156 mm2) multi-crystalline silicon (mc-Si) solar cells have been demonstrated, equating to an absolute efficiency gain of 1.58% compared to a conventional solar cell. The corresponding module power is 270.3 W, a 20 W increase over a conventional 60-cell mc-Si module of the same dimensions. These results demonstrate a successful transfer of advanced techniques from laboratory to large scale industrial production, which promote the mc-Si solar cells taking a big step forward in solar cells applications.
Co-reporter:Tuo Zheng, Hongmei Deng, Wenliang Zhou, Pingxiong Yang, Junhao Chu
Materials Letters 2016 Volume 185() pp:380-383
Publication Date(Web):15 December 2016
DOI:10.1016/j.matlet.2016.09.022
•Ferroelectric Fe-doped PTO prepared by a solid state reaction method was studied.•The Eg of xPTFO decreases markedly with Fe content, expressed by (2.78–5.05x) eV.•Induction of ferromagnetism in nonmagnetic perovskite PTO by Fe3+ doping.•Magnetic switching in xPTFO is due to ferromagnetic–antiferromagnetic competition.The PbTi1-xFexO3-δ (xPTFO) ferroelectric ceramics have been studied by means of structural characterizations, optical and magnetic measurements. All the samples show a tetragonal perovskite structure with uniform grains. In Fe-doped PbTiO3, the oxygen-vacancies were confirmed by an X-ray photoelectron spectroscopy, which affect the materials’ optical and magnetic properties. The optical bandgap of xPTFO decreases significantly with increasing Fe content, expressed by (2.78–5.05x) eV. Magnetic measurements show a ferromagnetic-paramagnetic transition occurs in xPTFO ceramics, which can be attributed to the competition between ferromagnetic and paramagnetic/antiferromagnetic components. These findings will open up a route to design optimal perovskite compounds for photovoltaic devices and magnetic storage.
Co-reporter:Wenliang Zhou, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Letters 2016 Volume 181() pp:178-181
Publication Date(Web):15 October 2016
DOI:10.1016/j.matlet.2016.06.032
•Well-crystallized KBNNO thin film was first prepared by a modified PLD method.•Near-stoichiometric KBNNO film possesses a pseudo-cubic perovskite structure.•Nanometer-sized regular and uniformly distributed grains shown in KBNNO SEM image.•The optical behavior of KBNNO film was assessed for potential solar application.Perovskite-type ferroelectrics are increasingly being studied for applications in solar-energy conversion because of their efficient ferroelectric polarization-driven carrier separation and above-bandgap generated photovoltages. (K,Ba)(Ni,Nb)O3−δ ferroelectric films, a highly promising and low-cost absorber layer material for solar cells, have been fabricated on Pt(111)/Ti/SiO2/Si(100) substrates for the first time, using a modified pulsed laser deposition method. Well-crystallized near-stoichiometric (K,Ba)(Ni,Nb)O3−δ film was obtained by adjusting the target–substrate distance to 50 mm and setting the substrate at an oblique angle of ~11° from the plume axis. Microstructural characterizations show the as-grown film exhibits a single-phase perovskite structure with a dense and uniform surface. The optical absorption spectrum of (K,Ba)(Ni,Nb)O3−δ has two main peaks, i.e., a significant peak at the intermediate energy adjacent to a much larger peak at higher photon energy, which indicates intraband multiple electronic transition. The present results could be crucial for potential solar-energy device applications.
Co-reporter:Jinyu Cui, Huiyi Cao, Wenliang Zhou, Leilei Chen, Xuezhen Zhai, Lu Yu, Tuo Zheng, Pingxiong Yang
Materials Letters 2016 Volume 163() pp:28-31
Publication Date(Web):15 January 2016
DOI:10.1016/j.matlet.2015.10.043
•The CuCrO2 powers were prepared by the solid state reaction method.•Phase evolution is detected by XRD and Raman measurements.•Morphological analysis shows a transition from hexagonal to blocky structure.•The optical characterization of CuCrO2 powder has been investigated.CuCrO2 powders have been prepared by solid state reaction method followed by thermal treatments at 850 °C for 4 h in air. Effects of mole ratio variation (Cr/Cu=1.03, 1, 0.95) on the morphological, structural and optical properties of CuCrO2 powders have been investigated. Both X-ray diffraction and Raman measurements indicate that the CuCrO2 powders belong to the delafossite structure. The Cr/Cu ratio drives the structural phase transition from multiphase coexistence to single CuCrO2 phase. Morphological images reveal that the CuCrO2 powder (Cr/Cu=1) exhibits a clear lamellae hexagonal structure whereas the Cr-rich sample (Cr/Cu=1.03) shows a distinct blocky structure, which possibly attributed to the Cr2O3 grains coating on those of CuCrO2. The optical absorption spectra of the as-prepared powders show that CuCrO2 has an indirect band gap of 1.64 eV.
Co-reporter:Wenliang Zhou, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Letters 2016 Volume 185() pp:323-326
Publication Date(Web):15 December 2016
DOI:10.1016/j.matlet.2016.09.012
•PTO, PTNO and PTPO films were prepared on quartz substrates by a sol-gel method.•PTNO and PTPO films present small band-gaps of 2.67 eV and 2.55 eV, respectively.•Induction of ferromagnetism in nonmagnetic perovskite PTO by d8 ions doping.•Pb(Ti0.85M0.15)O3-δ films have potential applications in PVs and magnetic storage.The Pb(Ti1-xMx)O3-δ (M=Ni and Pd) ferroelectric thin films prepared by a sol-gel technique have been studied by means of structural characterizations, optical and magnetic measurements. X-ray diffraction and Raman scattering results reflect the visible changes in average structure. Moreover, d8M2+ doping has important effects on the energy band structure and magnetic orderings. Optical transmittance spectra analysis indicates that Pb(Ti0.85Ni0.15)O3-δ and Pb(Ti0.85Pd0.15)O3-δ thin films present small band-gaps of 2.67 eV and 2.55 eV, respectively. Also, the as-grown Pb(Ti0.85M0.15)O3-δ thin films show room-temperature ferromagnetism, in contrast to PbTiO3 which is diamagnetic. A bound magnetic polaron model can be employed to explain the observed ferromagnetic behavior.
Co-reporter:Wenliang Zhou, Hongmei Deng, Tuo Zheng, Pingxiong Yang, Junhao Chu
Materials Letters 2016 Volume 177() pp:1-4
Publication Date(Web):15 August 2016
DOI:10.1016/j.matlet.2016.04.167
•BTO, BTCO, BTCPO films were prepared on quartz substrates by a sol–gel method.•The BTCPO has a narrow Eg of 2.21 eV due to new states in an electronic structure.•Excellent combination of saturation magnetization and coercivity shown in BTCPO.•The BTCPO film has potential applications in storage and optoelectronic devices.Thin films of perovskite-type Ba(Ti0.75Ce0.125Pd0.125)O3−δ (BTCPO) have been investigated by means of microstructural characterizations, optical and magnetic measurements. X-ray diffraction patterns show that the BTCPO exhibits a centrosymmetric cubic perovskite structure accompanied by the grain refinement. Raman spectroscopy, however, shows the symmetry of crystalline structures is locally lowered by the presence of dopants, significantly deviating from the ideal Pm3m space group, possibly due to an increased internal strain. The BTCPO film possesses a narrow bandgap of 2.21 eV, much smaller than BaTiO3 (3.5 eV), which originates from new states in the electronic structure with the presence of Pd2+. Magnetic hysteresis loops indicate that the BTCPO film exhibits an excellent combination of saturation magnetization and coercivity at room temperature.
Co-reporter:Huiyi Cao, Hongmei Deng, Wenliang Zhou, Jiahua Tao, Leilei Chen, Ling Huang, Lin Sun, Fangyu Yue, Pingxiong Yang, Junhao Chu
Journal of Alloys and Compounds 2015 Volume 651() pp:208-213
Publication Date(Web):5 December 2015
DOI:10.1016/j.jallcom.2015.08.148
•CIAS have been prepared via the selenization of sputtered precursor thin films.•The pure phase purity can be obtained by manipulating the Cu content.•Microstructural parameters of CIAS films have little relevance with the Cu content.•The band gap of CIAS films shows a declining trend with the increase of Cu content.Cu(In, Al)Se2 (CIAS) thin films are deposited onto the soda-lime glass substrates via the selenization of sputtered Cu–In–Al precursors, have been investigated by means of microstructural and optical characterization. The influence of Cu content ranges from 0.61 to 1.05 on the microstructure and optical properties of CIAS thin films is assessed. X-ray diffraction patterns and Raman scattering spectra reveal that the phase purity of thin films is strongly relied on the Cu content. The secondary phases, such as Cu(In, Al)3Se5 and CuSe have been detected in the Cu-poor and Cu-rich films, respectively. However, the microstructural parameters (e.g. tetragonal distortion, crystal strain and dislocation density) of thin films have little relevance with the Cu content. X-ray photoelectron spectroscopy analysis confirms the pure phase formation of CIAS was located at the Cu/(In + Al) ratio of 0.83. The corresponding scanning electronic microscopy image shows that the film exhibits a relatively flat-grained and compact morphology. Additionally, optical transmittance measurement indicates that the band gap of CIAS thin films shows a declining trend with the increase of Cu/(In + Al) ratios. The results are significant to gain insight into the Cu–In–Al–Se system materials for thin film solar cell application.
Co-reporter:Xiankuan Meng, Hongmei Deng, Jun Zhang, Wenliang Zhou, Jiahua Tao, Lin Sun, Fangyu Yue, Pingxiong Yang, Junhao Chu
Journal of Alloys and Compounds 2015 Volume 646() pp:68-72
Publication Date(Web):15 October 2015
DOI:10.1016/j.jallcom.2015.06.006
•The growth orientation of CFTSe can be manipulated by controlling the reaction time.•Formation of crystal surface along (220/204) will restrain the (002) and (103) peak.•Bond-length of Cu–Se presents a non-monotonic change with the reaction time.•Mechanisms associated with tuning in structure and optical properties were discussed.•An opportunity for effective bond-tuning by varying the reaction time was provided.Cu2FeSnSe4 (CFTSe) thin films were formed by selenization of sputtered metal layers on glass substrates. X-ray diffraction and Raman spectra show that all peaks are belong to the CFTSe. Moreover, the bond-length of Cu–Se (dCu-Se) decreases from 2.463 to 2.443 Å, and then increases to 2.450 Å as reaction time elevate to 20 min. The tuning of grain growth along (220/204)-orientation can be achieved by varying the reaction time, also, the intensity of (002) and (103) peaks will be restrained with the more formation of crystal surface along (220/204)-orientation. Based on the Keating's mode and combine with dCu-Se, it is well expounded the A1 modes of CFTSe which exhibit a red-shift with the reaction time up to 15 min and then an opposite trend (i.e. blue-shift). Furthermore, the various hybridizations of Cu d and Se p orbital, which is connected with the dCu-Se, drive the redistribution of the band gap of CFTSe. The values of the band gap are 1.26, 1.25 1.14 and 1.23 eV for thin films selenized using 5, 10, 15 and 20 min, respectively. These results are helpful to understand the structure, crystal orientation control and band gap variations in polycrystalline Cu–Fe–Sn–Se(S) system materials deeply.
Co-reporter:Xiankuan Meng, Huiyi Cao, Hongmei Deng, Wenliang Zhou, Jiahua Tao, Lin Sun, Fangyu Yue, Pingxiong Yang, Junhao Chu
Journal of Alloys and Compounds 2015 Volume 644() pp:354-362
Publication Date(Web):25 September 2015
DOI:10.1016/j.jallcom.2015.05.044
•CFTSe and CIAS have been fabricated by RF-magnetron sputtering and RTP process.•The elevated temperatures result in a shortened trend of bond-length for CFTSe.•The Al content decreases with increasing temperatures which tune the band-gap.•The mechanism associated with tuning in crystal lattice and band-gap were discussed.•Voc of CFTSe and CIAS are 76 and 353 mV, respectively.Two Cu-based selenide semiconductors Cu2FeSnSe4 (CFTSe) and Cu(In, Al)Se2 (CIAS) have been fabricated using radio-frequency magnetron sputtering followed rapid thermal processing. For CFTSe, the elevated selenization temperatures ranging from 460 to 520 °C result in a shortened trend of bond-length of cationic–anionic, corresponding to more formation heat released during the selenization process, which favors the grain growth. However, according to the strain calculation, the lattice strain of the thin film selenized at 500 °C presents a minimum value, meaning the fewer defects in thin films. As for the other Cu-based material CIAS, the band-gap (Eg) is determined by the band-to-band electron transition from valence band to conduction band directly. The Al content will affect the hybridization degree of Al–Se which will drive the redistribution of electrons in the conduction band, and then optimize the band-structure. The conduction band minimum shifts into band-gap due to the less amount of Al during the selenization process at higher temperature. In addition, both of CFTSe and CIAS transform into single-phase with large grain size and dense morphologies when selenized at 500 and 540 °C, respectively. The electrical properties of CFTSe (Eg ∼ 1.16 eV) and CIAS (Eg ∼ 1.34 eV), which open circuit voltage is 76 mV and 353 mV, respectively, are also researched.
Co-reporter:Leilei Chen, Hongmei Deng, Jinyu Cui, Jiahua Tao, Wenliang Zhou, Huiyi Cao, Lin Sun, Pingxiong Yang, Junhao Chu
Journal of Alloys and Compounds 2015 Volume 627() pp:388-392
Publication Date(Web):5 April 2015
DOI:10.1016/j.jallcom.2014.12.047
•Cu2MnxZn1−xSnS4 (CMZTS) thin film have been firstly prepared by sol–gel technique.•XRD and Raman demonstrate the structural transition from kesterite to stannite with increasing Mn content.•The band gap energy of CMZTS thin films can be tuned almost linearly between 1.23 and 1.51 eV varying with Mn compositions.Cu2Zn1−xMnxSnS4 (CMZTS) thin films with composition controllability and tunable band gap have been firstly prepared by sol–gel technique followed by a post-annealing treatment at 580 °С for 10 min in nitrogen gas atmosphere. Effects of Mn variation in CMZTS thin films with x = 0.0–1.0 on the morphological, structural, and optical properties have been investigated. XRD and Raman studies reveal the incorporation of Mn into Cu2ZnSnS4 (CZTS) thin films, and demonstrate the structural transition from kesterite to stannite with increasing Mn content. SEM images show that compact, homogeneous and densely packed grains could be formed. Furthermore, UV–vis spectroscopy indicate that the band gaps of the CMZTS films can be tuned almost linearly between 1.23 and 1.51 eV with a small bowing constant of the band gap (∼0.10 eV), which confirms the good miscibility of the alloyed constituents in the crystal lattice.
Co-reporter:Jun Zhang, Hongmei Deng, Jun He, Xiankuan Meng, Tantan Liu, Lin Sun, Pingxiong Yang, Junhao Chu
Applied Surface Science 2015 Volume 326() pp:211-215
Publication Date(Web):30 January 2015
DOI:10.1016/j.apsusc.2014.11.131
Highlights
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The CIAS thin films are prepared by RF sputtering.
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The substitution of In by Al in the films result in the lattice shrink.
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The electrical properties of the interface for AZO/CIAS have been investigated.
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The film is potential to be used for photodetector applications.
Co-reporter:X. Z. Zhai, H. M. Deng, W. L. Zhou, P. X. Yang, J. H. Chu and Z. Zheng
RSC Advances 2015 vol. 5(Issue 100) pp:82351-82356
Publication Date(Web):23 Sep 2015
DOI:10.1039/C5RA16030H
KBiFe2O5, a highly promising multiferroic for perovskite solar cells, has been fabricated using a one-step thermal treatment method. The resulting products were characterized by X-ray diffraction, scanning electron microscopy and ultraviolet-visible-near-infrared spectroscopy. The effect of temperature on the formation of KBiFe2O5 polycrystallites was assessed, and we found that the reaction temperature is the key factor in determining the optical properties of the final products. Pure multiferroic KBiFe2O5 forms at a temperature of 850 °C with a narrow band gap of 1.65 eV, which is due to the stronger covalent character of Fe–O in FeO4 than that in FeO6 accompanying the inverted t2g/eg orbitals of tetrahedra. The magnetic transition from paramagnetism to ferromagnetism corresponds to the site of Fe3+, and the magnetic moment modification in the ferromagnetic phase in KBiFe2O5 could be correlated with the temperature and distortion of the unit cell. These results are helpful in the deeper understanding of the relationship between the crystal structure and the physical properties in perovskite-like oxides and show the potential role such materials can play in perovskite solar cells and multiferroic applications.
Co-reporter:Leilei Chen, Hongmei Deng, Jiahua Tao, Huiyi Cao, Ling Huang, Lin Sun, Pingxiong Yang and Junhao Chu
RSC Advances 2015 vol. 5(Issue 102) pp:84295-84302
Publication Date(Web):28 Sep 2015
DOI:10.1039/C5RA14595C
Earth-abundant Cu2MnSnS4 (CMTS) thin films were fabricated through a non-toxic spin-coating technique. The precursor solution is based on a 2-methoxyethanol solvated thiourea complex with acetyl-acetone used as an additive agent, and the spin-coated films were post-annealed at 570 °C under a N2 atmosphere. The influence of annealing time on the structure, composition, morphology, and optical properties of the processed precursor films has been studied in detail. We found that a longer annealing time during CMTS growth can improve the phase purity, promote the preferred orientation along the (112) direction, and enhance grain growth in the micrometer range. Film annealed for 10 min gives a pure CMTS phase, whereas other films annealed for lower and/or higher than 10 min (especially 13 min) can form secondary phases (i.e., SnS, MnS). The band gap energy is estimated as 1.63–1.18 eV for post-annealed films depending on the heat treatment, compared to 1.69 eV for as-prepared film. An efficiency of 0.49% for the device fabricated here has been achieved with an open-circuit voltage of 308.4 mV, a short-circuit current density of 4.7 mA cm−2, and a fill factor of 33.9%. It offers a new research direction for the application of a CMTS absorber layer in low-cost solar cells.
Co-reporter:Yingbin Zhang, Jianmei Xu, Jing Mao, Jiahua Tao, Hui Shen, Yifeng Chen, Zhiqiang Feng, Pierre J. Verlinden, Pingxiong Yang and Junhao Chu
RSC Advances 2015 vol. 5(Issue 81) pp:65768-65774
Publication Date(Web):27 Jul 2015
DOI:10.1039/C5RA11224A
An extensive program of series extended sequential long-term reliability stress including thermal cycling (TC) 600, damp heat (DH) 3000, 600 hours potential induced degradation (PID) and humidity freeze (HF) 50 were performed on silicon wafer-based traditional backsheet modules and double glass photovoltaic (PV) modules. The relative module maximum power (Pmax) degradations of traditional backsheet modules are 3.87%, 7.34%, 13.3%, 33.73% and those of double glass modules are 2.78%, 3.12%, 2.27%, 2.72%, respectively. From all the above results, HF50 has a greater impact on Pmax degradation of traditional backsheet modules, and a strong correlation is thereby found between the Water Vapor Transmission Rate (WVTR) of the backsheet and the Pmax degradation. Traditional backsheet modules have higher WVTR and greater Pmax degradation, while double glass modules are impermeable and have much lower Pmax degradation. The key factor for excellent performance of Si wafer-based double glass PV modules is replacing the polymer backsheet by a glass panel with impermeability to water vapor, which enables double glass modules to offer much higher reliability and longer durability.
Co-reporter:Xiankuan Meng, Huiyi Cao, Hongmei Deng, Wenliang Zhou, Jun Zhang, Ling Huang, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Science in Semiconductor Processing 2015 Volume 39() pp:243-250
Publication Date(Web):November 2015
DOI:10.1016/j.mssp.2015.05.007
Cu-based semiconductors Cu2FeSnSe4 (CFTSe) and Cu(In, Al)Se2 (CIAS) have been fabricated using radio-frequency magnetron sputtering combined with rapid thermal selenization processing. For CFTSe, the heating rate ranging from 60 to 150 °C/min results in a difference in structure, morphology and optical properties. Thin film exhibits a pure phase structure, smooth surface and a band gap of 1.19 eV as the heating rate elevated to 90 °C/min. Furthermore, the CFTSe thin film selenized at 90 °C/min own the smallest value of cell volume compared with the others samples, which represents a more stable structure. In terms of the other Cu-based material CIAS, three different selenization pressures, i.e., 1, 5 and 10 Torr, have been employed for CIAS preparation. Thin film transforms into single phase with dense morphology along with the pressure of 1 Torr. The diverse band gap of CIAS thin films from 1.34 to 2.18 eV attribute to two reasons: (i) the various Al content will affect the hybridization degree of Al–Se, and finally tunes the band structure, (ii) amounts of CuSe has a certain degree of effect on the band gap of the CIAS. In addition, the electrical properties of CFTSe and CIAS are also researched with the open circuit voltage (Voc) of 94 and 365 mV, respectively, signifying potential applications of CFTSe and CIAS for the thin film solar cells.
Co-reporter:Wenliang Zhou, Hongmei Deng, Huiyi Cao, Jun He, Jian Liu, Pingxiong Yang, Junhao Chu
Materials Letters 2015 Volume 144() pp:93-96
Publication Date(Web):1 April 2015
DOI:10.1016/j.matlet.2015.01.038
•(Bi1–xSmx)(Fe0.95Mn0.05)O3 films were deposited on quartz substrates by sol-gel.•The Sm and Mn co-doping BiFeO3 thin films result in structural distortion.•The optical band gap of the thin films could be tuned by the Sm content.•The thin films have potential applications in storage and optoelectronic devices.Multiferroic (Bi1−xSmx)(Fe0.95Mn0.05)O3 (xBSFMO, x=0.00, 0.03, 0.06, and 0.09) films were deposited on the quartz substrates by a sol–gel technique. X-ray diffraction patterns indicate that all the films exhibit a polycrystalline perovskite structure with a high degree of (110) preferred orientation. The Sm and Mn co-doping at A- and B-site of BiFeO3 (BFO) results in structural distortion, improves surface morphology and reduces the average grain size of the films. With increasing x from 0.00 to 0.09, the optical band gap of xBSFMO films increases and can be expressed by (2.60+0.8x) eV, which may be due to Burstein–Moss effect. Compared with Mn-doped BFO film, the saturation magnetization (MS) of the (Sm, Mn) co-doped BFO films are significantly enhanced, which provides potential applications in information storage.
Co-reporter:Xuezhen Zhai, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Letters 2015 Volume 158() pp:266-268
Publication Date(Web):1 November 2015
DOI:10.1016/j.matlet.2015.05.164
•Bi1−xTbxFeO3 films were deposited on the quartz substrates by sol–gel technique.•Tb-doping at A-site of BiFeO3 improves surface morphology.•Tb-doped BiFeO3 films exhibit higher ferromagnetism.•The optical band gap of Bi1−xTbxFeO3 films could be tuned by the Tb content.Single-phase multiferroic Bi1-xTbxFeO3 (xBTFO, x=0.00, 0.03, 0.06 and 0.09) films were deposited on quartz substrates by chemical solution deposition. X-ray diffraction patterns indicate that all films exhibit a distorted pseudo-tetragonal perovskite structure with a high degree of (110) preferred orientation. The Tb-doping at A-site of BiFeO3 (BFO) results in lattice contraction, improves surface morphology and reduces the average grain size of the films. One A mode and five E modes of films are observed in Raman scattering spectra, and the position of A mode shifts to higher wavenumber with the increasing of x due to the enhanced Bi–O covalent by Tb doping. With increasing x from 0.00 to 0.09, the saturation magnetization of xBTFO films increases and can be expressed by Ms=(34.6x+1.1) emu/cm−3, originating from different bond interactions between 4f, 5d orbitals of Tb–O and 6p orbitals of Bi–O. Compared with BFO film, the band gap of xBTFO films decreases, which is mainly due to the increased the tailing of the conduction band edge into the band-gap, which is leading to decreasing the band gap.
Co-reporter:Huiyi Cao, Hongmei Deng, Jiahua Tao, Wenliang Zhou, Xiankuan Meng, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2015 Volume 157() pp:42-44
Publication Date(Web):15 October 2015
DOI:10.1016/j.matlet.2015.05.021
•The Se content in thin films is deeply dependent on the selenization time.•Phase evolution is detected by XRD and Raman measurements.•Morphological show a transition from scattered particles to densely-packed.•The electrical characterization of Cu(In, Al)Se2 solar cells has been investigated.Cu(In, Al)Se2 (CIAS) thin films were synthesized by selenization of stacked metallic precursors for different times ranging from 5 to 30 min. Compositional study demonstrates that the Se content in the CIAS thin films is significantly dependent on the selenization time. Both X-ray diffraction and Raman analysis reveal that the selenization time drives structural phase transition from coexisting phases of CuInSe2 and CIAS to single CIAS phase. The insufficient selenization time during the grain growth process would induce the formation of impurity phase and structural defects in CIAS films. Morphological studies further indicate a gradual transition from the coarse surface containing scattered micron-sized particles to the relatively smooth and compact morphology as the selenization time increases. The solar cell device with the CIAS absorber selenized for 20 min achieves the highest open circuit voltage of 487 mV.
Co-reporter:Xiankuan Meng, Hongmei Deng, Jun He, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2015 Volume 151() pp:61-63
Publication Date(Web):15 July 2015
DOI:10.1016/j.matlet.2015.03.046
•XRD indicates that CFTS is pure phase with the strain of 8.29×10−3.•Raman and IR of CFTS present two A1, two B and three E optical modes.•The Eg of CFTS is 1.42 eV which consists with the ideal Eg (1.4 eV).•Reason for diverse values of Eg of CFTS based on the band theory is discussed.•Voc and Jsc of CFTS are 110 mV and 2.5 mA cm−2, respectively.Cu2FeSnS4 (CFTS) thin film has been synthesized by rapid thermal annealing sulfurization of radio-frequency magnetron sputtered precursor. X-ray diffraction pattern indicates that all phases belong to CFTS with tetragonal structure. The strain which exists in the film is calculated to be 8.29×10−3 using the Williamson–Hall method. Raman spectrum and infrared reflectivity present two A1, two B and three E optical vibration modes. The band gap of CFTS is evaluated to be 1.42 eV by the transmission spectrum. The electrical properties of CFTS with the structure of glass/Mo/CFTS/CdS/i-ZnO/AZO have also been discussed. The open circuit voltage (Voc) is 110 mV, short circuit density (Jsc) is 2.5 mA cm−2 and fill factor (FF) is 26.3%. These results are helpful to the preparation and further study of CFTS thin films for the solar cell application.
Co-reporter:Ling Huang, Hongmei Deng, Jun He, Xiankuan Meng, Jiahua Tao, Huiyi Cao, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2015 Volume 159() pp:1-4
Publication Date(Web):15 November 2015
DOI:10.1016/j.matlet.2015.05.170
•CZGS films with different Cu contents were prepared by sputtering method.•Cu-rich films exhibit large grain size compared to those of Cu-poor films.•Square resistance decrease from 14.2 to 1.3 kΩ/□ with increasing grain size.•Band gaps of the films decrease from 1.97 eV to 1.80 eV as Cu content increases.•Reason for diverse values of Eg of CZGS based on the band theory is discussed.Cu2ZnGeS4 thin films with different Cu contents were synthesized by sulfurization of radio-frequency magnetron sputtered precursors. Microstructural characterizations using scanning electron microscopy and X-ray diffraction reveal that all of the as-prepared Cu2ZnGeS4 thin films are well crystallized and present a visible increase of grain size with increasing Cu content. In this case, the corresponding square resistance of these films is found to decrease from 14.2 to 1.3 kΩ/□. Furthermore, ZnS phase can be observed in the Cu-poor sample determined by Raman spectroscopy. Band gaps of the films decrease from 1.97 eV to 1.80 eV with increasing of Cu/(Zn+Ge) ratio from 0.93 to 1.13. These results are helpful to further study on Cu2ZnGeS4 thin films that are applicable for manufacturing solar cell.
Co-reporter:Jian Liu, Hongmei Deng, Liping Zhu, Kezhi Zhang, Xiankuan Meng, Huiyi Cao, Pingxiong Yang, Junhao Chu
Applied Surface Science 2014 Volume 316() pp:78-81
Publication Date(Web):15 October 2014
DOI:10.1016/j.apsusc.2014.07.179
Highlights
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Bi1−xEuxFeO3 films were grown on (1 0 0) SrTiO3 substrates by PLD technique.
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The band gap of the films decreases with increasing Eu content.
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The saturation magnetization of the films increases with increasing Eu content.
Co-reporter:Jian Liu, Hongmei Deng, Huiyi Cao, Xuezhen Zhai, Jiahua Tao, Lin Sun, Pingxiong Yang, Junhao Chu
Applied Surface Science 2014 Volume 307() pp:543-547
Publication Date(Web):15 July 2014
DOI:10.1016/j.apsusc.2014.04.071
Highlights
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The BEFOx thin films were grown on LaNiO3 coating Si substrates by pulsed laser deposition.
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Optical properties of the films were first analyzed by spectroscopic ellipsometry.
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The band gap of the films decreases with increasing Eu composition.
Co-reporter:Jian Liu, Hongmei Deng, Xuezhen Zhai, Tie Lin, Xiangjian Meng, Yuanyuan Zhang, Wenliang Zhou, Pingxiong Yang, Junhao Chu
Materials Letters 2014 Volume 133() pp:49-52
Publication Date(Web):15 October 2014
DOI:10.1016/j.matlet.2014.06.142
•The BiFe1−xZnxO3 films were prepared on quartz substrates by sol–gel technique.•The band gap of the films increases with increasing Zn composition.•The saturation magnetization of the films increases with Zn content.The multiferroic BiFe1−xZnxO3 (BFZOx, x=0, 0.03, 0.06, and 0.09) films have been prepared on quartz substrates by the sol–gel technique. X-ray diffraction indicates that BFZOx films characterize the distorted rhombohedral perovskite structure. Scanning electron microscopy (SEM) shows that Zn doping can improve the crystallinity of BFZOx (x=0.06 and 0.09) films. With increasing Zn composition, the fundamental absorption edges of BFZOx films show blue shift. Compared with BiFeO3 film, the saturation magnetization (Ms) of BFZOx (x=0.03, 0.06, and 0.09) films is significantly enhanced, which provides potential applications in information storage.
Co-reporter:Hui Kong, Jun He, Ling Huang, Liping Zhu, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2014 Volume 116() pp:75-78
Publication Date(Web):1 February 2014
DOI:10.1016/j.matlet.2013.10.112
•CIGS thin films were deposited on soda lime glass (SLG) substrates by RF magnetron sputtering process from a single target.•It has better crystalline quality of CIGS thin film deposited at lower working pressure.•The rms roughness of the CIGS thin films decreases with the increasing of the working pressures which is related to the grain size of different thin films.CIGS thin films were deposited on soda lime glass substrates by RF magnetron sputtering process from a single target at different working pressure. All CIGS thin films were deposited on heated substrates without post-selenization process. Energy dispersive X-ray results show CIGS thin films are Cu-poor state. The Cu content in the films decrease as the working pressure increased. The results of X-ray diffraction and Raman spectra analysis indicate that all CIGS thin films are the chalcopyrite-type structure and pure phase. It has better crystalline quality of CIGS thin film deposited at lower working pressure. However, the rms roughness of the CIGS thin films decreases with the increasing of the working pressures which is related to the grain size of different thin films. The grain size of thin films deposited at lower working pressure is larger. Further transmission spectra demonstrate the optical band gaps of all CIGS thin films.
Co-reporter:Xiankuan Meng, Hongmei Deng, Jun He, Liping Zhu, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2014 Volume 117() pp:1-3
Publication Date(Web):15 February 2014
DOI:10.1016/j.matlet.2013.11.107
•Cu2FeSnSe4 (CFTSe) thin film was synthesized by physical method.•Both XRD and Raman results indicate CFTSe thin film has stannite structure.•The band gap is 1.10 eV, this process is a suitability approach for solar cells.Cu2FeSnSe4 (CFTSe) thin film was synthesized on glass substrate by two-stage process, which is RF magnetron sputtering and following post-annealing process. The chemical composition is close to the stoichiometry of 2:1:1:4 measured by energy dispersive X-ray spectroscopy. X-ray diffraction pattern indicates that all phases belong to CFTSe. It indicates that there are no additional or intermediate phases. A1 mode of the film is observed in Raman scattering spectra. From the results of XRD and Raman spectrum analysis, the structure of CFTSe can be determined. The film exhibits stannite structure (space group 14¯2m) with lattice parameters a=5.6889 Å and c=11.284 Å. Further transmission spectra demonstrates that the band gap of thin film is 1.10 eV.
Co-reporter:Hui Kong, Jun He, Xiankuan Meng, Liping zhu, Jiahua Tao, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2014 Volume 118() pp:21-23
Publication Date(Web):1 March 2014
DOI:10.1016/j.matlet.2013.12.050
•CIGS precursors were deposited directly by the radio frequency magnetron sputtering process from a single target.•The selenization process was used to improve the Se content in the thin films.•The samples selenized using 5 mg and 10 mg of Se powder have better crystallinity.•The samples selenized using Se powders have better surface morphology.Cu(In,Ga)Se2 (CIGS) precursors were deposited on Mo-coated soda lime glass substrates by a radio frequency magnetron sputtering process from a single target. The selenization of CIGS precursor layer was performed by using a rapid thermal process. Energy dispersive X-ray analysis results show CIGS thin films are in a Cu-poor state. The films selenized with 0 mg and 5 mg are deficient in the Se element. However, films selenized using 20 mg show a slightly rich Se content. The results of X-ray diffraction and Raman spectra analysis indicate that the samples are the chalcopyrite-type structures and in pure phase. Both XRD and Raman scattering results indicate the samples selenized using 5 mg and 10 mg of the Se powder have better crystallinity. Furthermore, the samples selenized using Se powders have better surface morphology. In summary, 10 mg of Se powder for usage is the desired candidate.
Co-reporter:Jianjun Tian, Huiping Gao, Hongmei Deng, Lin Sun, Hui Kong, Pingxiong Yang, Junhao Chu
Journal of Alloys and Compounds 2013 Volume 581() pp:318-323
Publication Date(Web):25 December 2013
DOI:10.1016/j.jallcom.2013.07.105
•Ni doping decreases the activation energy for the anatase-to-rutile transformation.•With increasing Ni content, the reversible ferromagnetism is found.•Sharp decrease of the EOBG at low Ni content is mainly related to phase composition.Ni-doped TiO2 films were deposited on Si(1 0 0) substrates by sol–gel technique. X-ray photoelectron spectroscopy analysis suggests that the valence of Ni ion is in +2 and oxygen vacancies increase with increasing Ni content. X-ray diffraction measurements indicate that Ni doping catalyzes the anatase-to-rutile transformation (ART) of TiO2 films, which is due to the decrease of the ART activation energy. The reversible ferromagnetism of the samples with Ni fraction is found, which is due to an anatase-to-rutile junction destroying an F-center bound magnetic polaron. Optical properties of Ni-doped TiO2 films were studied by the ellipsometric spectra. With increasing Ni content, the optical band gap of TiO2 films is decreased from 3.56 to 3.34 eV, which may be related to phase composition and impurity band.
Co-reporter:Lin Peng, Hongmei Deng, Jianjun Tian, Qing Ren, Cheng Peng, Zhipeng Huang, Pingxiong Yang, Junhao Chu
Applied Surface Science 2013 Volume 268() pp:146-150
Publication Date(Web):1 March 2013
DOI:10.1016/j.apsusc.2012.11.176
Abstract
Multiferroic BiFe1−xCoxO3 (x = 0, 0.03, 0.05, 0.1) thin films have been prepared on quartz substrates using a sol–gel technique. X-ray diffraction data confirms that Co atoms have been successfully incorporated into the host lattice. The scanning electron microscopy (SEM) exhibits that the surface morphologies of BiFe0.97Co0.03O3 and BiFe0.95Co0.05O3 thin films become more compact and uniform. With increasing Co dopant, the position of A1-1 and E-4 modes shift towards the lower wavenumber indicates that Co doping induces structural distortion of BiFeO3. With increasing Co composition, the fundamental absorption edges of BiFe1−xCoxO3 films show red shift. Furthermore, transmittance spectra demonstrates that the optical band gap of BiFe1−xCoxO3 films decreases from 2.66 eV to 2.53 eV with the increase of Co from x = 0 to 0.1. At the wavelength of 720 nm, the refractive index decreases and the extinction coefficient increases with increasing the amount of Co. Optical properties reveal that Co doping in BiFeO3 provides preliminary research for optoelectronic devices and infrared detectors. Compared with BiFeO3 prepared under similar conditions, the remanent magnetization Mr of BiFe1−xCoxO3 (x = 0.03, 0.05, 0.1) thin films significantly enhanced, which provides potential applications in information storage.
Co-reporter:Hurui Yan, Hongmei Deng, Nuofan Ding, Jun He, Lin Peng, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters 2013 Volume 111() pp:123-125
Publication Date(Web):15 November 2013
DOI:10.1016/j.matlet.2013.08.075
•Multiferroic Bi0.9La0.1Fe1−xCrxO3 thin films were deposited.•The optical and magnetic properties of the films were studied.•The films have potential applications in information storage.Bi0.9La0.1Fe1−xCrxO3 (x=0.03, 0.05 and 0.07) thin films were deposited on LaNiO3/Si and quartz by RF magnetron sputtering, respectively. X-ray diffraction patterns indicate that all phases belong to BiFeO3, and no secondary phase is detected. Three A1 modes and six E modes of the films are observed in Raman scattering spectra, and the A1-1 peak position shows red shift with the increasing of x, which indicates that the Cr doping induces more structural distortion. The band gap of the films for x=0.03, 0.05 and 0.07 can be expressed by (2.99−x) eV, which is due to the Cr doping that increases the tailing of conduction band edge into the band gap. With the Cr content increasing from 3% to 7%, the remnant magnetization and the magnetization at 10 kOe of the films show about 202% and 55% addition, respectively.
Co-reporter:Jianjun Tian;Huiping Gao;Hui Kong
Nanoscale Research Letters 2013 Volume 8( Issue 1) pp:
Publication Date(Web):2013 December
DOI:10.1186/1556-276X-8-533
Transition metal (TM)-doped TiO2 films (TM = Co, Ni, and Fe) were deposited on Si(100) substrates by a sol–gel method. With the same dopant content, Co dopants catalyze the anatase-to-rutile transformation (ART) more obviously than Ni and Fe doping. This is attributed to the different strain energy induced by the different dopants. The optical properties of TM-doped TiO2 films were studied with spectroscopic ellipsometry data. With increasing dopant content, the optical band gap (EOBG) shifts to lower energy. With the same dopant content, the EOBG of Co-doped TiO2 film is the smallest and that of Fe-doped TiO2 film is the largest. The results are related to electric disorder due to the ART. Ferromagnetic behaviors were clearly observed for TM-doped TiO2 films except the undoped TiO2 film which is weakly magnetic. Additionally, it is found that the magnetizations of the TM-doped TiO2 films decrease with increasing dopant content.
Co-reporter:Huiping Gao, Jianjun Tian, Hui Kong, Pingxiong Yang, Weifeng Zhang, Junhao Chu
Surface and Coatings Technology 2013 Volume 228() pp:162-166
Publication Date(Web):15 August 2013
DOI:10.1016/j.surfcoat.2013.04.024
•Optical properties of mixed crystal Ti0.95Ni0.05O2 films were studied by fitting SE.•Correlation between rutile content and refractive index abides by Drude's model.•Study on the magnetic properties of mixed crystal Ti0.95Ni0.05O2 films.Ni-doped mixed crystal TiO2 films, Ti0.95Ni0.05O2, were fabricated on Si(100) substrates by sol–gel process. The influences of annealing times on the structural, optical and magnetic properties were investigated. X-ray diffraction measurement indicates that all the films include anatase and rutile phases. The optical constants were obtained by fitting ellipsometric spectra with Adachi's dielectric function model. With increasing rutile content, both the refractive index and the extinction coefficient of the films increase, but the optical band gap EOBG is reduced. The refractive index at 600 nm abides by Drude's refractive index model with increasing rutile fraction. The magnetic evolution of the films is from ferromagnetic, to paramagnetic and then ferromagnetic states with increasing rutile fraction, which may be related to the magnetic polarons in the Ni-doped TiO2 films. The results indicate that optical and magnetic properties of Ni-doped TiO2 films can be tuned by controlling phase fraction.
Co-reporter:Jianjun Tian, Hongmei Deng, Lin Sun, Hui Kong, Pingxiong Yang, Junhao Chu
Applied Surface Science 2012 Volume 258(Issue 11) pp:4893-4897
Publication Date(Web):15 March 2012
DOI:10.1016/j.apsusc.2012.01.108
Abstract
The Ni-doped TiO2 films were synthesized on quartz substrates by the sol–gel method. Results from X-ray diffraction and Raman spectra indicate that Ni doping catalyzes the anatase-to-rutile transformation. When Ni content is up to 10 mol%, the transformation has been finished. The dielectric functions of Ni-doped TiO2 films were extracted by fitting transmittance spectra according to the Adachi's dielectric function model. The optical band gap decreases from 3.64 eV to 3.51 eV with increasing Ni content. The results suggest that the acceleration of phase change and variation of optical properties may be related to defects due to Ni doping.
Co-reporter:Nuofan Ding, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Letters 2012 Volume 82() pp:71-73
Publication Date(Web):1 September 2012
DOI:10.1016/j.matlet.2012.05.025
Multiferroic BiFe1 − xZnxO3 (0 ≤ x ≤ 0.10) thin films were prepared on LaNiO3 coating Si substrates by pulsed laser deposition. X-ray diffraction data confirmed the substitutions of Zn into the Fe site. The films are the dominant orientation of (101). Three A1 and five E modes are observed in Raman spectra. With increasing x, the position of the Raman active modes shift to higher wavenumber, and the full width at half maximum becomes smaller. At the photon energy of 2 eV, the refractive index is 2.71, and the extinction coefficient is close to zero. The band gap increases with the Zn amount, which may be caused by Burstein–Moss effect.Highlights► Zn-doped BiFeO3 films were grown on LaNiO3/Si substrates by PLD technique. ► Optical properties of the films were first analyzed by Spectroscopic Ellipsometry. ► Raman spectra show blue shift of the active modes with increasing Zn amount. ► The band gap of the films decreases with increasing Zn composition.
Co-reporter:Huan Deng;Hongmei Deng
Journal of Materials Science: Materials in Electronics 2012 Volume 23( Issue 6) pp:1215-1218
Publication Date(Web):2012 June
DOI:10.1007/s10854-011-0575-7
Multiferroic BiCrxFe1−xO3 (BCFO) (0 ≤ x ≤ 0.12) thin films were fabricated on silicon substrates by sol–gel technique. The microstructure and properties of the films are characterized using X-ray diffraction, spectroscopic ellipsometry, micro-Raman spectrometry and a Modular Control system. The BCFO films are the rhombohedral structure with the Cr content up to 7%. Raman scattering spectra of the BCFO films demonstrate the transformation of structure with the Cr content exceeding 10%. The band gap of the BCFO films is from 2.53 to 2.82 eV with the Cr content being from 0 to 12%. The magnetization of the BCFO films is significantly enhanced with the increasing of the Cr content.
Co-reporter:Jianjun Tian, Hongmei Deng, Lin Sun, Hui Kong, Pingxiong Yang, Junhao Chu
Thin Solid Films 2012 Volume 520(Issue 16) pp:5179-5183
Publication Date(Web):1 June 2012
DOI:10.1016/j.tsf.2012.03.125
Co-doped TiO2 thin films were synthesized on quartz substrates by sol–gel method. Atomic force microscopy results indicate that the surfaces of the Ti1 − xCoxO2 (0 ≤ x ≤ 0.10) films become smooth and compact with increasing Co content. X-ray diffraction results show that all the films are rutile phase structure and Co doping leads to lattice contraction. X-ray photoelectron spectroscopy results reveal that the predominant oxidation state of Co is divalent. Peak positions of Raman-active modes (B2g, A1g and Eg) shift to lower frequency with increasing Co content. The refractive index n at 670 nm from transmittance spectra increases with increasing Co content. The OBG varies between 3.10 and 3.26 eV. Note that optical band gap (OBG) first increases and then decreases with increasing Co content, reaching its maximum value when x is 0.03. These results suggest that the increasing mechanism of OBG is related to the decrease of grain size, compressive stress, and reduction of rutile TiO2, and the decreasing mechanism of OBG is involved with defect and impurity. The competition of the two mechanisms leads to the strange change of OBG.Highlights► Ti1 − xCoxO2 thin films (0 ≤ x ≤ 0.1) were fabricated by the sol–gel method. ► Increase in Co contents results in Raman shifts to lower frequencies. ► The packing density increases with increasing Co doping. ► The optical band gap increases and then decreases with the increasing Co content. ► The optical band gap varies between 3.1 and 3.26 eV.
Co-reporter:Jianjun Tian, Hongmei Deng, Lin Sun, Hui Kong, Pingxiong Yang, Junhao Chu
Physica E: Low-dimensional Systems and Nanostructures 2011 Volume 44(Issue 3) pp:550-554
Publication Date(Web):December 2011
DOI:10.1016/j.physe.2011.09.020
The influences of Co doping on the anatase-to-rutile transformation of TiO2 thin films have been investigated by Raman spectroscopy and X-ray diffraction. Raman spectra and XRD patterns for the samples of various Co concentrations present a clear evolution of TiO2 with different anatase-to-rutile ratios. The fraction of rutile phase increases gradually with increasing Co contents. When Co content exceeds 7 mol%, anatase phase is not detected in the samples. The results may be related to the oxygen vacancies, which are introduced by Co doping. According to the Adachi model, optical constant was extracted by spectroscopic ellipsometry. It is found that the refractive index n increases with increasing Co content from 2.29 to 2.4, and that the optical band gap decreases and varies with increment of Co content between 3.6 and 3.38 eV. This may be related to the changes in film density and band gap tailed due to the Co doping.Graphical abstractThe dielectric functions of the Co-doped TiO2 film from spectroscopic ellipsometry vary with photon energy. The fundamental absorption edges of the films from εi do not become sharp with increasing Co content. This suggests that Co doping affects the valence and conduction and then form the Urbach tail absorption characteristics.Highlights► Study of the anatase-to-rutile transformation in the Co-doped TiO2 thin films. ► Influence of the Co doping on the activity energy of grain growth of rutile phase. ► Optical properties of the Co-doped TiO2 films by spectroscopic ellipsometry.
Co-reporter:Zhenlun Zhang;Hongmei Deng
Journal of Materials Science: Materials in Electronics 2011 Volume 22( Issue 5) pp:488-491
Publication Date(Web):2011 May
DOI:10.1007/s10854-010-0165-0
Ferroelectric Bi2VO5.5 thin films were fabricated on p-type (100) Si substrates by sol–gel method and then annealed at different temperatures. The microstructures and surface morphologies of the Bi2VO5.5 thin films were examined by X-ray diffraction and atomic force microscope, respectively. The results indicate that the Bi2VO5.5 thin films show high c-axis preferred orientation and are compatible well with p-type Si substrates. The capacitance–voltage characteristics of Pt/Bi2VO5.5/Si capacitors measured at 1 MHz shows a clockwise hysteresis loop. The memory window of the hysteresis loop is 0.42 V with the gate voltage from −4 to 4 V. It is found that the memory window may be determined by the competition between ferroelectric polarization and charge injection.
Co-reporter:Dongji Huang, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Letters 2010 Volume 64(Issue 20) pp:2233-2235
Publication Date(Web):31 October 2010
DOI:10.1016/j.matlet.2010.07.020
Single-phase multiferroic BiFeO3 thin films have been prepared on LaNiO3/Si(100) and Si(100) wafer via sol–gel technique. The films are polycrystalline with preferring orientation of (101). The film has a conspicuous absorption in the blue and green light region, and band gap of 2.74 eV. The refractive index and the extinction coefficient of the film is about 2.36 and 0.06 at 600 nm, 2.26 and close to zero in the range of 800–1200 nm, respectively. The films also exhibit favorable ferroelectric and dielectric properties. A large photo induced open-circuit voltage was observed, indicating that the film exhibits photovoltaic behaviours.
Co-reporter:Jing Kong, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Chemistry and Physics 2009 Volume 114(2–3) pp:854-859
Publication Date(Web):15 April 2009
DOI:10.1016/j.matchemphys.2008.10.049
High-quality antimony-doped tin dioxide (SnO2:Sb) thin films with various concentrations of Sb have been prepared on Si (1 1 1) wafer by sol–gel technique. The microstructure, surface morphology, composition and optical properties of the films are characterized using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. It is found that the films are the dominant orientation of (1 0 1) with rutile structure of SnO2, Sb dopant causes the peak positions in XRD patterns to shift slightly instead of introducing new phases, and the average grain size of the films is about 26 nm. Optical constant, refraction index n from 1.55 to 1.95 in the visible spectral region, was determined through multilayer analyses on their respective pseudo-dielectric functions. It is also found that the optical constants depend strongly on the layers of films, annealing temperature and the concentration of Sb dopant.
Co-reporter:Zhipeng Liu, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Letters 2009 Volume 63(Issue 30) pp:2622-2624
Publication Date(Web):31 December 2009
DOI:10.1016/j.matlet.2009.09.028
The ferroelectric thin films of Fe-doped BaTiO3 and undoped BaTiO3 were prepared on LaNiO3 coating Si substrates by sol–gel technique. It was found that a small amount of Fe dopant could significantly enhance the ferroelectric properties of the BaTiO3 thin film. The remnant polarization of Fe-doped BaTiO3 thin film at room temperature reached to 14.9 μC/cm2. The loss tangent, compared to the undoped BaTiO3 film, was increased with frequency increasing and the dielectric constant was decreased. The possible mechanism of enhanced ferroelectric properties of Fe-doped BaTiO3 thin film was discussed. The results show the potential role of Fe dopant in improving the ferroelectric properties of BaTiO3 thin film.
Co-reporter:Ming Guo, Hongmei Deng, Pingxiong Yang, Junhao Chu
Materials Letters 2009 Volume 63(Issue 17) pp:1535-1537
Publication Date(Web):15 July 2009
DOI:10.1016/j.matlet.2009.04.004
Bi2VO5.5 ferroelectric thin films were fabricated on LaNiO3/Si(100) substrate via chemical solution deposition. Ferroelectric and dielectric properties of the thin films annealed at 500–700 °C were studied. The thin film annealed at 700 °C exhibited more favorable ferroelectric and dielectric properties than those annealed at lower temperatures. The values of remnant polarization 2Pr and coercive field Ec for the film annealed at 700 °C are 10.62 µC/cm2 and 106.3 kV/cm, respectively. The leakage current of the film is about 1.92 × 10− 8 A/cm2 at 6 V. The possible mechanism of the dependence of electrical properties of the films on the annealing temperature was discussed.
Co-reporter:Hongmei Deng;Jing Kong
Journal of Materials Science: Materials in Electronics 2009 Volume 20( Issue 11) pp:1078-1082
Publication Date(Web):2009 November
DOI:10.1007/s10854-008-9829-4
The optical and structural characteristics of Sb-doped SnO2 films grown on Si (111) substrates by modified sol–gel technique have been investigated. The films are both polycrystalline and retain the SnO2 peaks of the rutile phase corresponding to (110), (101), (211) and (310) without any other phases appearing. X-ray photoelectron spectroscopy shows the peaks corresponding to the Sn 3d5/2, the O 1s, and the Sb 3d5/2 states. Refractive indices n, and extinction coefficients k, as functions of the incident photon energy were obtained for the films by spectroscopic ellipsometry measurement, and the refractive indices were from 1.95 to 1.50 at 2.6 eV with increasing Sb content. The optical constants, n and k, of the films can be controlled by variable Sb content. These results are important for the applications in integrated optical devices.
Co-reporter:Pingxiong Yang, Hongmei Deng, Meirong Shi, Ziyang Tong, Sumei Qin
Materials Science and Engineering: B 2007 Volume 137(1–3) pp:99-102
Publication Date(Web):25 February 2007
DOI:10.1016/j.mseb.2006.10.017
High quality SrBi2TaNbO9 (SBTN) ferroelectric thin films were fabricated on platinized silicon by pulsed laser deposition. Microstructure and ferroelectric properties of the films were characterized. Optical fatigue (light/bias) for the thin films was studied and the average remanent polarization dropped by nearly 55% due to the bias/illumination treatment. Optical properties of the thin films were studied by spectroscopic ellipsometry (SE) from the ultraviolet to the infrared region. Optical constants, n ∼ 0.16 in the infrared region and n ∼ 2.12 in the visible spectral region, were determined through refractive index functions. The band gap energy is estimated to be 3.93 eV.
Co-reporter:Jiejin Yu, Hongmei Deng, Jiahua Tao, Leilei Chen, Huiyi Cao, Lin Sun, Pingxiong Yang, Junhao Chu
Materials Letters (15 March 2017) Volume 191() pp:
Publication Date(Web):15 March 2017
DOI:10.1016/j.matlet.2016.12.067
•CMTS film was the first time to be synthesized via electrodeposition method.•It was the first time for two-step electrodeposition method to be mentioned.•Phase-pure CMTS thin film can be prepared by using FTO as substrate.•The results offer a novel research direction for preparing CMTS thin films.Cu2MnSnS4 (CMTS) thin film was the first time to deposit on the seeded fluorine doped tin oxide (FTO) substrate via sulfurization of electrodeposited Cu-Sn/Mn metal precursors. X-ray diffraction patterns and Raman measurements reveal the formation of stannite structure CMTS film with pure phase. The morphological and chemical composition studies indicate the formation of compact and homogenous CMTS thin film with Cu-poor and Mn-rich composition. The band gap of CMTS thin film is evaluated to be about 1.35 eV by the transmission spectrum. The results offer a novel research direction for preparing pure-sulfide CMTS thin films by using a simple, facile, green and low-cost electrodeposition method.
Co-reporter:Qiao Zhang, Hongmei Deng, Leilei Chen, Jiahua Tao, Jiejin Yu, Pingxiong Yang, Junhao Chu
Materials Letters (15 April 2017) Volume 193() pp:
Publication Date(Web):15 April 2017
DOI:10.1016/j.matlet.2017.02.002
•Novel CCTS film was synthesized via direct liquid method.•The properties of CCTS thin films depend strongly on the post-annealing temperature.•Characterize the structural properties of Cu2CdSnS4 thin films.•The band gap value of CCTS thin films decreases with the increasing annealing temperature.Cu2CdSnS4 (CCTS) appears to be a promising absorber material for thin film solar cells and have been deposited on glass substrate by a direct liquid coating method. Effects of sulfurization temperature on the composition, morphology, structural and optical properties of CCTS have been investigated systematically. X-ray diffraction and Raman measurements reveal that the increase of temperature would lead to an improved crystallinity of CCTS and the secondary phase of Cu2S confirmed by Raman spectrum can be suppressed by increasing annealing temperature. The grain size of CCTS thin films is demonstrated to be improved as the annealing temperature increases with slight S-poor and Sn-poor condition. All the thin films have estimated band gap in the range of 1.31–1.14 eV, which decreases almost linearly with the increasing temperature and can be well suited for use in photovoltaics and thermoelectricity.
Co-reporter:Tantan Liu, Hongmei Deng, Huiyi Cao, Wenliang Zhou, Jun Zhang, Jian Liu, Pingxiong Yang, Junhao Chu
Journal of Crystal Growth (15 April 2015) Volume 416() pp:78-81
Publication Date(Web):15 April 2015
DOI:10.1016/j.jcrysgro.2015.01.022
•The Sb2Te3 films were prepared by a pulsed laser deposition technique.•The microstructure of Sb2Te3 films was changed with the increase of substrate temperature.•The optical band gap and TCR of Sb2Te3 film are carefully investigated.•The Sb2Te3 films have promising applications in infrared device.Sb2Te3 films were deposited using pulsed laser deposition technique onto substrates heated up to different temperatures. According to X-ray diffraction analysis, the films were well crystallized with preferred orientation of (00l), and belong to the rhombohedral structure. Raman spectrum explained the change of microstructure by the lattice vibration modes, revealing the dependent relationship between the nucleation rate and substrate temperatures. The scanning electron microscope images exhibit uniform and smooth films surface morphologies. Additionally, the absorption coefficient of the film is above 104 cm−1 in the infrared range and the corresponding optical band gap is around 0.32 eV. The resistivity of the films decreases as the substrate temperature increases, and the temperature coefficient of resistance for Sb2Te3 films is 0.15% K−1. These results imply that Sb2Te3 films have a potential application for uncooled infrared detection.
