•Al-Mg-Ti-B coatings have been prepared at room temperature by HIPIMS.•The negative bias voltage had a strong effect on the chemical composition of coatings.•The mechanical properties of coatings were improved by reducing the number of BO bonds.•The values of H and E of the HIPIMS Al-Mg-Ti-B coatings were as high as 37 GPa and 348 GPa, respectively.In this work, Al-Mg-Ti-B coatings were synthesized at room temperature via high power impulse magnetron sputtering (HIPIMS). The as-deposited Al-Mg-Ti-B coatings exhibited a dense and X-ray amorphous microstructure. It was demonstrated that the chemical composition and mechanical properties of Al-Mg-Ti-B coatings were significantly altered by applying different negative bias voltages during the HIPIMS process. The XPS results showed that oxygen concentration in the coatings was reduced from ~ 22 at.% to ~ 8 at.% and the number of oxygen-boron bonds dropped with an increasing bias voltage, which contributed significantly to the improved mechanical properties. Nano-indentation results showed that the nano-hardness and elastic modulus of the HIPIMS Al-Mg-Ti-B coatings were as high as 37 GPa and 348 GPa, respectively.

Natural-superlattice-structured/intergrowth CaBi2Nb2O9-Bi4Ti3O12 (CBNO-BIT) ferroelectric thin films were successfully prepared via a magnetron sputtering process. XRD and TEM analysis revealed the [Bi2O2-(CaNb2O7)-Bi2O2-(Bi2Ti3O10)]n intergrowth structure of the film, as well as a (200)/(020) texture. XPS and EDS results confirmed that the film composition is close to the chemical stoichiometry. With its microstructure being successfully tailored at the nanoscale, the CBNO-BIT film exhibits good electrical properties, including a large dielectric constant (εr ∼390), a high piezoelectric coefficient (d33 ∼90 pm/V) as well as a high energy storage density (WE ∼76 J/cm3). Finally, the intergrowth nature of the film was verified by the measured temperature-dependent dielectric response (C-T).

Reducing thermal budget of functional layers grown on Si substrates has become a necessity for their integration into contemporary manufacturing technology of microelectronics. The work presented here exemplifies one of such efforts by preparing barium titanate (BaTiO3 or BTO) films at temperatures as low as 350 °C on Si substrates via a CMOS-compatible RF-magnetron sputtering process. In this study, X-ray diffraction (XRD) results reveal that use of LaNiO3 (LNO) buffer layer successfully induces BaTiO3 film’s transition from polycrystalline to highly c-axis oriented tetragonal in low temperature range. Moreover, encouraged by BaTiO3 films prepared at 500 °C that shows a nearly uniform (00l) orientation with excellent ferroelectric properties (Pr ~ 2.6 μC/cm2, Ec ~ 100 kV/cm, d33 ~ 150 pm/V), we further push the deposition temperature down to 350 °C. While showing reduced crystallinity, these lower temperature films still possess good dielectric properties which are characterized by a stable dielectric constant of 110 ± 5 and a small dielectric loss between 0.7 and 3 % in the frequency range of [1 kHz, 2 MHz]. We believe the finding of high quality BaTiO3 films achievable at 350 °C is meaningful in that it paves the road for BaTiO3’s real application in Si based CMOS technology.

•Epitaxial BaTiO3/(La0.5Sr0.5)CoO3 heterostructures were successfully grown on various single-crystal substrates.•Film/electrode interface state is the dominant contributor to the fluctuations of the physical properties.•The leakage current characteristics of BTO films can be well described by a modified-Schottky-model.•A large space charge density contributes to the shrinking/tilting of the loops and provides high energy-storage density.Epitaxial BaTiO3 (BTO) films were deposited on (La0.5Sr0.5)CoO3 buffered (001)-oriented YAlO3, LaAlO3, (La0.5Sr0.5)(Al0.5Ta0.5)O3, and SrTiO3 single-crystal substrates using radio-frequency magnetron sputtering. XRD analyses identified that the actual in-plane misfit strains are an order of magnitude less than the unrelaxed lattice misfit (the relaxation of the film/substrate internal stresses). The dielectric properties, polarization and leakage current performances all exhibit slightly the substrate-dependent behavior, which can be mainly attributed to the difference of the film/electrode interface-state parameters. A modified Schottky model was employed to describe the leakage current behaviors. Large space-charge densities calculated with this theory achieved on the order of 1019 cm−3 for all BTO films, which will significantly contribute to shrinking and tilting of our P-V loops. One possible potential application for ferroelectric films with such characteristic is to provide high storage density of capacitive energy.Download high-res image (253KB)Download full-size image

In this work, strain engineered polycrystalline thin films (∼250 nm) of bismuth layer-structured ferroelectric (BLSF) CaBi2Nb2O9 (CBNO) were prepared by using a radio frequency (RF) magnetron sputtering technique. XRD analysis revealed that the films were (200)/(020) and (00l) textured with a large in-plane tensile stress. Cross-sectional TEM analyses confirmed the bismuth layered-structure, as well as crystalline orientations and a strain-controlled growth mode of the grains. Result of a quantitative XPS analysis revealed that the composition of the film is close to the chemical stoichiometry. Excellent electrical properties were achieved in the CBNO films, including a high dielectric constant (∼280 @5 kHz), a small dielectric loss (tgδ ≤ 1.6% up to an applied electric field of ∼1200 kV/cm) and a large polarization (Pr ≈ 14 μC/cm2 @ 1 kHz).

Epitaxial BiFeO3 films (∼0.5 μm thick) were prepared on (100) LaAlO3 substrates using radio-frequency (RF) magnetron sputtering. A good heteroepitaxial growth of BiFeO3 films was confirmed by XRD and TEM analyses. While co-existing rhombohedral and tetragonal-like phases were revealed near the bottom interface of the films in the form of elastic domains to relax the initial misfit stresses, the bulk of the films consists of only the rhombohedral phase. The sputtering atmosphere, i.e. the flow ratio of Ar/O2 at a fixed sputtering pressure, did not affect the epitaxial growth and phase structure of the BiFeO3 films. Instead, it showed significant influences on the electrical properties, i.e. dielectric behavior, as well as the ferroelectric and leakage current characteristics. It was shown that, among the four films deposited at different Ar/O2 flow ratios (2:1, 3:1, 4:1 and 6:1), the film with a 4:1 flow ratio has the best overall electrical properties, which can be attributed to its stoichiometric physical vapor growth at a balanced Ar/O2 flow ratio. It showed a remnant polarization (2Pr) of 150 μC cm−2 and a low leakage current density of about 3.6 × 10−4 A cm−2 at 200 kV cm−1.

Epitaxial BaTiO3 ferroelectric films with (001), (110), and (111) orientations were, grown on SrRuO3 buffered SrTiO3 substrates via a radio-frequency magnetron sputtering method. The effects of the orientation on dielectric response were systematically investigated. We found that the (110)-oriented film exhibited the largest dielectric permittivity, tunability and phase transition temperature, whereas the (111)-oriented film demonstrated the best figure of merits if the dielectric loss was taken into consideration. The large anisotropic dielectric behavior, which is predominantly attributed to the differences of polarization states in these orientation engineered BaTiO3/SrTiO3 heterostructures, was observed. These results suggest the (111)-oriented film may be an attractive candidate for applications in dielectric tunable devices.

•TiAlN/TiAlSiN/Si3N4 SSAC is prepared using dc magnetron sputtering technique.•The SSAC exhibits an average absorptance of 0.938 and emittance of 0.099.•The spectral properties of the SSAC are stable in air up to 500 °C.Spectrally selective TiAlN/TiAlSiN/Si3N4 multilayer coatings were deposited on stainless steel (SS) plate using a reactive direct current magnetron sputtering technique. In this tandem absorber system, TiAlN, TiAlSiN and Si3N4 act as the main absorbing layer, the semi-absorbing layer and the antireflection layer, respectively. An average absorptance (α) of 0.938 and emittance (ε) of 0.099 were achieved in coatings prepared under optimized conditions, which exhibit a fine-grained morphology and an amorphous microstructure as evidenced by SEM and XRD analysis, respectively. Absorptance and emittance data, as well as Raman spectra were collected for coatings exposed to different levels of thermal stresses (2 h in air @200 °C, 300 °C, 400 °C, 500 °C, 600 °C). These heat treated coatings showed negligible to small degradations in their selective absorbing capabilities as compared with the as-grown ones. There was no significant change of the coatings in their morphology or composition after the heat treatments, as evidenced by the SEM and Raman spectra analysis, respectively. The spectral selectivity of the coatings remained stable after a heat-treatment at 272 °C in air for 300 h.

•The TiN/TiSiN/SiN SSACs are prepared using a dc reactive sputtering technique.•The SSACs exhibit an average absorptance of 0.95 and an emittance as low as 0.04.•The spectral properties of TiN/TiSiN/SiN SSAC are stable after 300 h annealing in air at 200 °C.TiN/TiSiN/SiN solar selective absorbing coatings (SSACs) with and without a copper underlayer were deposited on stainless steel (SS) substrates via dc reactive magnetron sputtering. In this SSAC, SS/Cu or SS, TiN, TiSiN and SiN act as the metal reflector layer, high metal volume fraction layer, low metal volume fraction layer and anti-reflection layer, respectively. An absorptance (α) of 0.95 and a total hemispherical emittance (ε (70 °C)) of 0.04 were achieved in coatings with Cu underlayer. On the other hand, the SS/TiN/TiSiN/SiN SSAC showed a similar absorptance (∼0.95) but a poorer emittance and solar selectivity. X-ray diffraction analysis showed that the Cu layer is polycrystalline, while TiN, TiSiN and SiN are amorphous. The chemical-bonding states of each layer of the TiN/TiSiN/SiN SSAC were analyzed by using X-ray photoelectron spectroscopy. The solar selective absorbing performance of the Cu/TiN/TiSiN/SiN SSAC did not show significant changes after they were heat-treated in vacuum up to 700 °C. Raman spectra and atomic force microscopy images were collected to illustrate the structural and morphological stabilities of this SSAC upon heating in vacuum. Lastly, heat treatments in air for 150 and 300 h based on the PC nomenclature were carried out to demonstrate long term thermal stability of SS/TiN/TiSiN/SiN.

Bi(Zn0.5,Ti0.5)O3 (BZT) doped Pb(Zr0.4,Ti0.6)O3 (PZT) films were fabricated using a chemical solution deposition method and were characterized intensively in the present work. It was discovered that the room temperature remnant polarization and zero-field longitudinal piezoelectric constant of the BZT-doped PZT film were enhanced by 23% and 30%, respectively, as compared with those of the undoped PZT film prepared under the same experiment conditions. In order to explain the improved ferroelectric properties, the phase structures of the BZT–PZT and undoped PZT films were experimentally investigated in a broad temperature range (from 30 to 600 °C) by using the high temperature two-dimensional X-ray diffraction method. It was found that the improvement in ferroelectricity does not correspond to an elevated Curie temperature (TC) or a substantially larger tetragonality (c/a). The difference on the change of TC by doping of Bi-based perovskites in PZT solid solutions between this work and some previous investigations was explained on the basis of Zr/Ti ratio, and the necessity of an in-depth theoretical investigation was addressed.Highlights► Pr and d33 of the fabricated films were enhanced by 23% and 30%, respectively. ► The phase transition process was investigated in a broad temperature range. ► Ferroelectricity improvement does not correspond to a high Curie temperature.

(1−x)BaTiO3-xBaSnO3 (BT-xBS, 0≤x≤0.20) perovskite thin films were deposited on Pt/Ti/Si substrates with uniaxial graded composition by using a dual-target combinatorial sputtering technique. These films were highly (101)-oriented and showed strong composition dependence in their electromechanical properties. The maximum value of the relative dielectric constant was 925 at around x=0.028, where the transverse piezoelectric coefficient |e31, f| also peaked at about 1.5–1.9 C/m2. This |e31, f| value is higher than those of epitaxial BaTiO3 thin films. Our results indicate that BT-xBS is a promising substitute of lead-based perovskites for applications in piezoelectric MEMS devices.

•TiAlN/TiAlSiN/Si3N4 SSAC is prepared using dc magnetron sputtering technique.•The SSAC exhibits an average absorptance of 0.938 and emittance of 0.099.•The spectral properties of the SSAC are stable in air up to 500 °C.Spectrally selective TiAlN/TiAlSiN/Si3N4 multilayer coatings were deposited on stainless steel (SS) plate using a reactive direct current magnetron sputtering technique. In this tandem absorber system, TiAlN, TiAlSiN and Si3N4 act as the main absorbing layer, the semi-absorbing layer and the antireflection layer, respectively. An average absorptance (α) of 0.938 and emittance (ε) of 0.099 were achieved in coatings prepared under optimized conditions, which exhibit a fine-grained morphology and an amorphous microstructure as evidenced by SEM and XRD analysis, respectively. Absorptance and emittance data, as well as Raman spectra were collected for coatings exposed to different levels of thermal stresses (2 h in air @200 °C, 300 °C, 400 °C, 500 °C, 600 °C). These heat treated coatings showed negligible to small degradations in their selective absorbing capabilities as compared with the as-grown ones. There was no significant change of the coatings in their morphology or composition after the heat treatments, as evidenced by the SEM and Raman spectra analysis, respectively. The spectral selectivity of the coatings remained stable after a heat-treatment at 272 °C in air for 300 h.

In this work, we report the polymorphic phase transitions(PPT) in ferroelectric Ba0.95Sr0.05ZrxTi(1-x)O3 (BSZT, x = 0.01–0.10) ceramics synthesized by using a solid-state reaction method. The doping elements and composition ratios were selected to create adjoining PPT phase boundaries near room temperature, hence to achieve a broadened peak of piezoelectric performance with respect to composition. The temperature-composition phase diagram was constructed and the effects of PPT on the electromechanical and ferroelectric properties of the ceramics were investigated. It was revealed that the two adjacent PPT regions at room temperature showed different characteristics in property enhancement. However, due to the proximity of the phase boundaries, Ba0.95Sr0.05ZrxTi(1-x)O3 ceramics in a fairly broad range of compositions (0.02 ≤ x ≤ 0.07) showed excellent piezoelectric properties, including a large piezoelectric constant (312 pC/N ≤ d33 ≤ 365 pC/N) and a high electromechanical coupling coefficient kp (0.42 ≤ kp ≤ 0.49).

In an attempt to build a CMOS-compatible process with reduced thermal budget for the integration of barium titanate ferroelectric films into Si-based MEMS and IC devices, BaTiO3 films were prepared on Pt/Ti/(1 0 0) Si substrate at 500 °C by a rf magnetron sputtering process without a post-growth annealing. Effects of substrate temperature, gas composition, gas pressure and target power on the microstructure of these films were analyzed in details. The BaTiO3 films deposited under the conditions of 500 °C substrate temperature, 120 W target power and 0.3 Pa gas pressure with a 4:1 Ar/O2 flow ratio displayed good ferroelectric and dielectric properties. The microstructure analysis by XRD and AFM indicated that these BaTiO3 films were polycrystalline with a preferred (0 0 1) orientation and a smooth surface with a Ra ∼ 1.7 nm. The twice remnant polarization 2Pr was 10.9 μC/cm2 @ 1 kHz, while the relative dielectric constant and dielectric loss tangent were measured to be 720/0.042 @ 1 kHz, and 360/0.038 @ 1 MHz, respectively.Highlights► BaTiO3 films were prepared on (1 0 0) Si substrates @ 500 °C by rf magnetron sputtering. ► The effects of gas pressure and target power on the property of BaTiO3 were studied. ► Under high target power, ferroelectric BaTiO3 films were obtained without annealing. ► These ferroelectric films showed a (0 0 1) texture and a smooth surface with Ra ∼ 1.7 nm. ► These films showed good ferroelectric and dielectric properties at room temperature.