Co-reporter:Riley Gatensby, Toby Hallam, Kangho Lee, Niall McEvoy, Georg S. Duesberg
Solid-State Electronics 2016 Volume 125() pp:39-51
Publication Date(Web):November 2016
DOI:10.1016/j.sse.2016.07.021
Two-dimensional (2D) transitional metal dichalcogenides (TMDs) are of major interest to the research and electrical engineering community. A number of TMDs are semiconducting and have a wide range of bandgaps, they can exhibit n- or p-type behaviour, and the electronic structure changes with the number of layers. These exceptional properties hold much promise for a host of electrical applications including low- or high power field-effect transistors, sensors and diodes. Moreover, the unique optical properties of TMDs make them attractive for optoelectronic applications such as light-emitting diodes, photodiodes, and photovoltaic cells. A prerequisite for all of these applications is a synthesis route which is well controlled, scalable, reproducible and compatible with semiconductor industry process flows. Thermally assisted conversion (TAC), a variant of chemical vapour deposition, shows much promise for meeting these requirements. Herein we review the current progress and challenges of research on 2D semiconducting materials for electronics with a special focus on TAC produced TMD thin films.
Co-reporter:Chanyoung Yim, Kangho Lee, Niall McEvoy, Maria O’Brien, Sarah Riazimehr, Nina C. Berner, Conor P. Cullen, Jani Kotakoski, Jannik C. Meyer, Max C. Lemme, and Georg S. Duesberg
ACS Nano 2016 Volume 10(Issue 10) pp:9550
Publication Date(Web):September 23, 2016
DOI:10.1021/acsnano.6b04898
Layered two-dimensional (2D) materials display great potential for a range of applications, particularly in electronics. We report the large-scale synthesis of thin films of platinum diselenide (PtSe2), a thus far scarcely investigated transition metal dichalcogenide. Importantly, the synthesis by thermally assisted conversion is performed at 400 °C, representing a breakthrough for the direct integration of this material with silicon (Si) technology. Besides the thorough characterization of this 2D material, we demonstrate its promise for applications in high-performance gas sensing with extremely short response and recovery times observed due to the 2D nature of the films. Furthermore, we realized vertically stacked heterostructures of PtSe2 on Si which act as both photodiodes and photovoltaic cells. Thus, this study establishes PtSe2 as a potential candidate for next-generation sensors and (opto-)electronic devices, using fabrication protocols compatible with established Si technologies.Keywords: low-temperature synthesis; optoelectronic devices; platinum diselenide; sensors; transition metal dichalcogenides; two-dimensional materials
Co-reporter:Nina C. Berner, Sinéad Winters, Claudia Backes, Chanyoung Yim, Kim C. Dümbgen, Izabela Kaminska, Sebastian Mackowski, Attilio A. Cafolla, Andreas Hirsch and Georg S. Duesberg
Nanoscale 2015 vol. 7(Issue 39) pp:16337-16342
Publication Date(Web):11 Sep 2015
DOI:10.1039/C5NR04772B
The non-covalent functionalisation of graphene is an attractive strategy to alter the surface chemistry of graphene without damaging its superior electrical and mechanical properties. Using the facile method of aqueous-phase functionalisation on large-scale CVD-grown graphene, we investigated the formation of different packing densities in self-assembled monolayers (SAMs) of perylene bisimide derivatives and related this to the amount of substrate contamination. We were able to directly observe wet-chemically deposited SAMs in scanning tunnelling microscopy (STM) on transferred CVD graphene and revealed that the densely packed perylene ad-layers adsorb with the conjugated π-system of the core perpendicular to the graphene substrate. This elucidation of the non-covalent functionalisation of graphene has major implications on controlling its surface chemistry and opens new pathways for adaptable functionalisation in ambient conditions and on the large scale.
Co-reporter:Sinéad Winters, Nina C. Berner, Rohit Mishra, Kim C. Dümbgen, Claudia Backes, Martin Hegner, Andreas Hirsch and Georg S. Duesberg
Chemical Communications 2015 vol. 51(Issue 94) pp:16778-16781
Publication Date(Web):28 Sep 2015
DOI:10.1039/C5CC06433C
An efficient, high-throughput method for the formation of densely packed molecular films on graphene is reported. The films exhibit high stability and remain intact during a subsequent derivatisation reaction, offering a versatile route for the non-covalent functionalisation of graphene.
Co-reporter:Christian Wirtz, Toby Hallam, Conor Patrick Cullen, Nina C. Berner, Maria O'Brien, Mario Marcia, Andreas Hirsch and Georg S. Duesberg
Chemical Communications 2015 vol. 51(Issue 92) pp:16553-16556
Publication Date(Web):24 Sep 2015
DOI:10.1039/C5CC05726D
This commmunication presents a study of atomic layer deposition of Al2O3 on transition metal dichalcogenide (TMD) two-dimensional films which is crucial for use of these promising materials for electronic applications. Deposition of Al2O3 on pristine chemical vapour deposited MoS2 and WS2 crystals is demonstrated. This deposition is dependent on the number of TMD layers as there is no deposition on pristine monolayers. In addition, we show that it is possible to reliably seed the deposition, even on the monolayer, using non-covalent functionalisation with perylene derivatives as anchor unit.
Co-reporter:Christian Wirtz;Nina C. Berner
Advanced Materials Interfaces 2015 Volume 2( Issue 14) pp:
Publication Date(Web):
DOI:10.1002/admi.201500082
Graphene has been long thought of as a perfect barrier material due to its impermeability to all gases as well as mechanical and chemical durability. Moreover, graphene layers are transparent and conductive, significantly widening the field of potential applications beyond simple barrier coatings. However, it is very challenging to realize such barriers on a macroscopic scale as immaculate large area films are not available. In this work, a highly effective oxygen gas barrier made from multiple layers of chemical vapor deposited graphene is presented. The individual graphene layers are stacked using a modified polymer-assisted transfer method, avoiding polymer residue yielding an oxygen-tight arrangement. A stack of three layers of graphene transmitted 6.9 cm3 m−2 d−1 of O2 which corresponds to 1.10 × 10−17 cm3 cm/cm2 s (cm Hg) when normalized to thickness and pressure. This is several orders of magnitude better than any macroscale graphene coating reported to date and performs on a level that can compete with most modern coatings while being much thinner and conductive.
Co-reporter:Hugo Nolan, Niall McEvoy, Maria O'Brien, Nina C. Berner, Chanyoung Yim, Toby Hallam, Aidan R. McDonald and Georg S. Duesberg
Nanoscale 2014 vol. 6(Issue 14) pp:8185-8191
Publication Date(Web):03 Jun 2014
DOI:10.1039/C4NR01528B
The electrochemical generation of hydrogen fuel via the proton reduction in the Hydrogen Evolution Reaction (HER) in aqueous media is currently dependent on the use expensive noble metal catalysts for which alternatives must be sought. Molybdenum disulfide (MoS2) has shown great promise as a suitable electrocatalyst in this regard. While many lab-scale experiments on the HER activity of this material have demonstrated its viability and explored some fundamental mechanistic features of HER at MoS2, these experimental techniques are often ill-suited to large scale production of such electrodes. In this study we present work on the fabrication of MoS2/pyrolytic carbon (PyC) electrodes via vapour phase sulfurization of Mo thin films. These hybrid electrodes combine the catalytic activity of MoS2 with the conductivity and stability of PyC, whilst using industrially compatible processing techniques. Structural defects in the sulfur lattice were found to be key catalytically active sites for HER and thinner MoS2 films displayed a higher quantity of these defects and, hence, an improved HER activity. The observed Tafel slope of 95 mV decade−1 is comparable to previous literature works on MoS2 HER performance.
Co-reporter:Hugo Nolan, Beatriz Mendoza-Sanchez, Nanjundan Ashok Kumar, Niall McEvoy, Sean O'Brien, Valeria Nicolosi and Georg S. Duesberg
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 6) pp:2280-2284
Publication Date(Web):16 Dec 2013
DOI:10.1039/C3CP54877E
Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications.
Co-reporter:Riley Gatensby, Niall McEvoy, Kangho Lee, Toby Hallam, Nina C. Berner, Ehsan Rezvani, Sinéad Winters, Maria O’Brien, Georg S. Duesberg
Applied Surface Science 2014 Volume 297() pp:139-146
Publication Date(Web):1 April 2014
DOI:10.1016/j.apsusc.2014.01.103
Highlights
- •
Controlled and scalable growth of 2D transition metal dichalcogenide thin films by vapour phase sulfurisation of predeposited metal films is demonstrated.
- •
These films are characterised thoroughly with assorted forms of spectroscopy and electron microscopy, evidencing their high quality.
- •
A simple integration scheme, based on complementary shadow masks, is proposed for the production of electronic devices from these films.
- •
A NH3 sensor, with a sensitivity of 400 ppb, is demonstrated.
Co-reporter:Maria O’Brien, Kangho Lee, Rachel Morrish, Nina C. Berner, Niall McEvoy, Colin A. Wolden, Georg S. Duesberg
Chemical Physics Letters 2014 Volume 615() pp:6-10
Publication Date(Web):5 November 2014
DOI:10.1016/j.cplett.2014.09.051
Highlights
- •
WS2 thin films are synthesised using a H2S plasma to sulphurise WO3 films.
- •
This is successful at temperature as low as 500 °C.
- •
The films produced can be contacted electrically and show a high sensitivity to NH3.
Co-reporter:Christian Wirtz, Kangho Lee, Toby Hallam, Georg S. Duesberg
Chemical Physics Letters 2014 Volumes 595–596() pp:192-196
Publication Date(Web):18 March 2014
DOI:10.1016/j.cplett.2014.02.003
Co-reporter:Kangho Lee;Riley Gatensby;Niall McEvoy;Toby Hallam
Advanced Materials 2013 Volume 25( Issue 46) pp:6699-6702
Publication Date(Web):
DOI:10.1002/adma.201303230
Co-reporter:Hye-Young Kim, Kangho Lee, Niall McEvoy, Chanyoung Yim, and Georg S. Duesberg
Nano Letters 2013 Volume 13(Issue 5) pp:2182-2188
Publication Date(Web):April 2, 2013
DOI:10.1021/nl400674k
We report the manufacture of novel graphene diode sensors (GDS), which are composed of monolayer graphene on silicon substrates, allowing exposure to liquids and gases. Parameter changes in the diode can be correlated with charge transfer from various adsorbates. The GDS allows for investigation and tuning of extrinsic doping of graphene with great reliability. The demonstrated recovery and long-term stability qualifies the GDS as a new platform for gas, environmental, and biocompatible sensors.
Co-reporter:Nanjundan Ashok Kumar, Hugo Nolan, Niall McEvoy, Ehsan Rezvani, Richard L. Doyle, Michael E. G. Lyons and Georg S. Duesberg
Journal of Materials Chemistry A 2013 vol. 1(Issue 14) pp:4431-4435
Publication Date(Web):19 Feb 2013
DOI:10.1039/C3TA10337D
An environmentally benign and scalable route for the production of gram scale quantities of nitrogen-doped graphene using a downstream microwave plasma source is reported. Simultaneous reduction and doping of graphene oxide is achieved and the process negates the need for high temperatures and toxic solvents associated with existing methods. This gas-phase low temperature process is completely dry and, thus, minimises re-aggregation of graphene flakes which is typically associated with liquid phase reduction methods. The resulting material has many potential uses, particularly in electrochemical energy.
Co-reporter:Chanyoung Yim, Niall McEvoy, Hye-Young Kim, Ehsan Rezvani, and Georg S. Duesberg
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 15) pp:6951
Publication Date(Web):June 14, 2013
DOI:10.1021/am400963x
The metal–semiconductor contact is one of the most critical factors that determine the performance of semiconductor devices such as Schottky barrier diodes (SBDs). SBDs between conductive carbon thin films and silicon have attracted attention due to their high performance and potential low cost of fabrication. Here, we introduce impedance spectroscopy (IS) as a powerful technique to characterize such SBDs. The electrical and structural characteristics of carbon–silicon SBDs between silicon and two different types of conductive carbon thin films have been investigated. Modeling the data with an extended equivalent circuit model reveals the effects of the metal electrode contacts of SBDs for the first time. From dc current–voltage measurements, diode parameters including the ideality factor, the Schottky barrier height, and the series resistance are extracted. Through use of analysis with IS, additional information on the Schottky contact is obtained, such as the built-in potential and more reliable barrier height values. Thus, IS can be utilized to analyze interfaces between metals and semiconductors in great detail by electrical means.Keywords: conductive carbon thin films; equivalent circuit model; impedance spectroscopy; interface analysis; metal−semiconductor contact; Schottky diode;
Co-reporter:Niall McEvoy, Hugo Nolan, Nanjundan Ashok Kumar, Toby Hallam, Georg S. Duesberg
Carbon 2013 Volume 54() pp:283-290
Publication Date(Web):April 2013
DOI:10.1016/j.carbon.2012.11.040
We report on an adjustable process for the functionalisation of graphene surfaces with a downstream plasma source. The parameters of oxygen plasma treatments are modified such that oxygenated functionalities can be added to the surface of graphene films prepared by chemical vapour deposition in a controlled manner. The nature of induced defects is investigated thoroughly using Raman and X-ray photoelectron spectroscopy. A massive change in the surface properties is observed through the use of contact angle and electrochemical measurements. We propose the usage of such plasma treatments to facilitate the addition of further functional groups to the surface of graphene. The incorporation of nitrogen into the graphene lattice by substitution of oxygenated functional groups is demonstrated outlining the validity of this approach for further functionalisation.
Co-reporter:Hugo Nolan, Niall McEvoy, Gareth P. Keeley, Stephen D. Callaghan, Cormac McGuinness and Georg S. Duesberg
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 42) pp:18688-18693
Publication Date(Web):25 Sep 2013
DOI:10.1039/C3CP53541J
Nitrogen-doped Pyrolytic Carbon (N-PyC) films were employed as an electrode material in electrochemical applications. PyC was grown by via non-catalysed chemical vapour deposition and subsequently functionalised via exposure to ammonia–hydrogen plasma. The electrochemical properties of the N-PyC films were investigated using the ferri/ferro-cyanide and hexaamine ruthenium(III) chloride redox probes. Exceptional electron transfer properties were observed and quantified for the N-PyC compared to the as-grown films. X-ray photoelectron spectroscopy confirmed the presence of nitrogen in edge plane graphitic configurations and the surface of the N-PyC was investigated using scanning electron microscopy and atomic force microscopy. The excellent electrochemical performance of the N-PyC, in addition to its ease of preparation, renders this material ideal for applications in electrochemical sensing.
Co-reporter:Kangho Lee, Vittorio Scardaci, Hye-Young Kim, Toby Hallam, Hugo Nolan, Brian E. Bolf, Gregory S. Maltbie, James E. Abbott, Georg S. Duesberg
Sensors and Actuators B: Chemical 2013 Volume 188() pp:571-575
Publication Date(Web):November 2013
DOI:10.1016/j.snb.2013.07.048
•We examine transparent and flexible ammonia gas sensors based on SWCNTs.•The AuNP decoration enhances ammonia sensitivity of the sensors.•The theoretical low detection limit corresponds with the experimental results.•The sensor is highly conductive and mechanically robust.We report on a high performance flexible and transparent chemical sensor based on functionalised single-walled carbon nanotubes (SWCNTs). The SWCNT films were spray-deposited on transparent and flexible plastic substrates, and subsequently decorated with Au nanoparticles (AuNPs) providing a facile and cheap fabrication route. The electrical resistance of the films changed remarkably upon exposure to ammonia (NH3), AuNP decoration enhanced sensitivity to 255 ppb (parts-per-billion), one of the lowest reported so far. The reported sensor performance is a huge improvement towards low power consumption and its room temperature operation augers well for use in mobile devices for environmental protection and air quality control.
Co-reporter:Niall McEvoy, Nikolaos Peltekis, Shishir Kumar, Ehsan Rezvani, Hugo Nolan, Gareth P. Keeley, Werner J. Blau, Georg S. Duesberg
Carbon 2012 Volume 50(Issue 3) pp:1216-1226
Publication Date(Web):March 2012
DOI:10.1016/j.carbon.2011.10.036
We report on an adjustable process for chemical vapour deposition of thin films of pyrolytic carbon on inert substrates using an acetylene feedstock. Through modification of the reaction parameters control over film thickness and roughness is attained. These conducting films can be deposited in a conformal fashion, with thicknesses as low as 5 nm and a surface roughness of less than 1 nm. The highly reliable, cost effective and scalable synthesis may have a range of applications in information and communications technology and other areas. Raman and X-ray photoelectron spectroscopies, as well as high resolution transmission electron microscopy are used to investigate the composition and crystallinity of these films. The suitability of these films as electrodes in transparent conductors is assessed through a combination of absorbance and sheet resistance measurements. The films have a resistivity of ∼2 × 10−5 Ωm but absorb strongly in the visible range. The electrochemical properties of the films are investigated and are seen to undergo a marked improvement following exposure to O2 or N2 plasmas, making them of interest as electrochemical electrodes.
Co-reporter:Nikolaos Peltekis, Shishir Kumar, Niall McEvoy, Kangho Lee, Anne Weidlich, Georg S. Duesberg
Carbon 2012 Volume 50(Issue 2) pp:395-403
Publication Date(Web):February 2012
DOI:10.1016/j.carbon.2011.08.052
This paper reports on the effects of growth, transfer and annealing procedures on graphene grown by chemical vapour deposition. A combination of Raman spectroscopy, electrical measurements, atomic force microscopy, and X-ray photoemission spectroscopy allowed for the study of inherent characteristics and electronic structure of graphene films. Contributions from contaminants and surface inhomogeneities such as ripples were also examined. A new cleaning and reconstruction process for graphene, based on plasma treatments and annealing is presented, opening a new pathway for control over the surface chemistry of graphene films. The method has been successfully used on contacted graphene samples, demonstrating its potential for in situ cleaning, passivation and interface engineering of graphene devices.
Co-reporter:Nikos Peltekis;Marcel Mausser;Shishir Kumar;Niall McEvoy;Chris Murray
Chemical Vapor Deposition 2012 Volume 18( Issue 1-3) pp:17-21
Publication Date(Web):
DOI:10.1002/cvde.201106925
Abstract
The advances in the use of a remote plasma in combination with a rapid radiative reactor in plasma-enhanced (PE) CVD is presented here. The characteristics and parameters of this system are fully analyzed and compared with conventional CVD growth methods. Growth of multi- and single-walled carbon nanotubes (CNTs) at low temperatures with high quality and reproducibility has been achieved in this way. Further, a new catalytic system, which gives dense multi-wall CNTs on metal substrates, is presented.
Co-reporter:Kangho Lee;Hye-Young Kim;Mustafa Lotya;Jonathan N. Coleman;Gyu-Tae Kim
Advanced Materials 2011 Volume 23( Issue 36) pp:4178-4182
Publication Date(Web):
DOI:10.1002/adma.201101013
Co-reporter:Gareth P. Keeley, Arlene O'Neill, Niall McEvoy, Nikos Peltekis, Jonathan N. Coleman and Georg S. Duesberg
Journal of Materials Chemistry A 2010 vol. 20(Issue 36) pp:7864-7869
Publication Date(Web):09 Aug 2010
DOI:10.1039/C0JM01527J
This paper describes the electron transfer properties of graphene nano-sheets (GNSs) immobilised on pyrolysed photoresist film (PPF) electrodes. The former are produced by the dispersion and exfoliation of graphite in dimethylformamide, and they are characterised using transmission electron microscopy, scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry and electrochemical impedance spectroscopy are used to quantify the effect of the GNSs on electrochemical surface area and on electron transfer kinetics. Compelling evidence is reported in relation to the importance of edge-plane sites and defects in the promotion of electron transfer at carbon nanostructures. A novel ascorbic acid (vitamin C) sensor is presented based on the PPF/GNS system, which is effective in the range 0.4 to 6.0 mM, with a 0.12 mM detection limit. The selectivity of the sensor is demonstrated using a commercially available vitamin C supplement. This is the first report of the electrochemical properties of graphene nano-sheets produced using liquid-phase exfoliation, and it will serve as an important benchmark in the development of inexpensive graphene-based electrodes with high surface area and electro-catalytic activity.
Co-reporter:Gareth P. Keeley, Niall McEvoy, Shishir Kumar, Nikos Peltekis, Marcel Mausser, Georg S. Duesberg
Electrochemistry Communications 2010 Volume 12(Issue 8) pp:1034-1036
Publication Date(Web):August 2010
DOI:10.1016/j.elecom.2010.05.017
This communication describes the electrochemical properties of thin pyrolytic carbon (PyC) films created using a reliable, non-catalytic chemical vapour deposition (CVD) process. After deposition, the electron transfer characteristics of the films are optimised using a simple oxygen plasma treatment. The redox probes Ru(NH3)63+/2+, Fe(CN)63−/4− and Fe3+/2+ are employed to demonstrate that the resulting material is endowed with a large electrochemical surface area and outstanding electron transfer properties. Atomic force microscopy (AFM), Raman and X-ray photoelectron spectroscopy (XPS) are used to elucidate the morphology and chemical composition of the electrode surfaces. This material represents a new class of carbon electrode, and its large densities of edge-plane sites and oxygenated functionalities make it an ideal candidate for electrochemical sensor applications.
Co-reporter:Martin Schreiber, Tarek Lutz, Gareth P. Keeley, Shishir Kumar, Markus Boese, Satheesh Krishnamurthy, Georg S. Duesberg
Applied Surface Science 2010 Volume 256(Issue 21) pp:6186-6190
Publication Date(Web):15 August 2010
DOI:10.1016/j.apsusc.2010.03.138
Abstract
Ultrathin conductive carbon layers (UCCLs) were created by spin coating resists and subsequently converting them to conductive films by pyrolysis. Homogeneous layers as thin as 3 nm with nearly atomically smooth surfaces could be obtained. Layer characterization was carried out with the help of atomic force microscopy, profilometry, four-point probe measurements, Raman spectroscopy and ultraviolet–visible spectroscopy. The Raman spectra and high-resolution transmission electron microscopy image indicated that a glassy carbon like material was obtained after pyrolysis. The electrical properties of the UCCL could be controlled over a wide range by varying the pyrolysis temperature. Variation in transmittance with conductivity was investigated for applications as transparent conducting films. It was observed that the layers are continuous down to a thickness below 10 nm, with conductivities of 1.6 × 104 S/m, matching the best values observed for pyrolyzed carbon films. Further, the chemical stability of the films and their utilization as transparent electrochemical electrodes has been investigated using cyclic voltammetry and electrochemical impedance spectroscopy.
Co-reporter:Gareth P. Keeley, Arlene O'Neill, Niall McEvoy, Nikos Peltekis, Jonathan N. Coleman and Georg S. Duesberg
Journal of Materials Chemistry A 2010 - vol. 20(Issue 36) pp:NaN7869-7869
Publication Date(Web):2010/08/09
DOI:10.1039/C0JM01527J
This paper describes the electron transfer properties of graphene nano-sheets (GNSs) immobilised on pyrolysed photoresist film (PPF) electrodes. The former are produced by the dispersion and exfoliation of graphite in dimethylformamide, and they are characterised using transmission electron microscopy, scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry and electrochemical impedance spectroscopy are used to quantify the effect of the GNSs on electrochemical surface area and on electron transfer kinetics. Compelling evidence is reported in relation to the importance of edge-plane sites and defects in the promotion of electron transfer at carbon nanostructures. A novel ascorbic acid (vitamin C) sensor is presented based on the PPF/GNS system, which is effective in the range 0.4 to 6.0 mM, with a 0.12 mM detection limit. The selectivity of the sensor is demonstrated using a commercially available vitamin C supplement. This is the first report of the electrochemical properties of graphene nano-sheets produced using liquid-phase exfoliation, and it will serve as an important benchmark in the development of inexpensive graphene-based electrodes with high surface area and electro-catalytic activity.
Co-reporter:Christian Wirtz, Toby Hallam, Conor Patrick Cullen, Nina C. Berner, Maria O'Brien, Mario Marcia, Andreas Hirsch and Georg S. Duesberg
Chemical Communications 2015 - vol. 51(Issue 92) pp:NaN16556-16556
Publication Date(Web):2015/09/24
DOI:10.1039/C5CC05726D
This commmunication presents a study of atomic layer deposition of Al2O3 on transition metal dichalcogenide (TMD) two-dimensional films which is crucial for use of these promising materials for electronic applications. Deposition of Al2O3 on pristine chemical vapour deposited MoS2 and WS2 crystals is demonstrated. This deposition is dependent on the number of TMD layers as there is no deposition on pristine monolayers. In addition, we show that it is possible to reliably seed the deposition, even on the monolayer, using non-covalent functionalisation with perylene derivatives as anchor unit.
Co-reporter:Hugo Nolan, Beatriz Mendoza-Sanchez, Nanjundan Ashok Kumar, Niall McEvoy, Sean O'Brien, Valeria Nicolosi and Georg S. Duesberg
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 6) pp:NaN2284-2284
Publication Date(Web):2013/12/16
DOI:10.1039/C3CP54877E
Herein we use Nitrogen-doped reduced Graphene Oxide (N-rGO) as the active material in supercapacitor electrodes. Building on a previous work detailing the synthesis of this material, electrodes were fabricated via spray-deposition of aqueous dispersions and the electrochemical charge storage mechanism was investigated. Results indicate that the functionalised graphene displays improved performance compared to non-functionalised graphene. The simplicity of fabrication suggests ease of up-scaling of such electrodes for commercial applications.
Co-reporter:Hugo Nolan, Niall McEvoy, Gareth P. Keeley, Stephen D. Callaghan, Cormac McGuinness and Georg S. Duesberg
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 42) pp:NaN18693-18693
Publication Date(Web):2013/09/25
DOI:10.1039/C3CP53541J
Nitrogen-doped Pyrolytic Carbon (N-PyC) films were employed as an electrode material in electrochemical applications. PyC was grown by via non-catalysed chemical vapour deposition and subsequently functionalised via exposure to ammonia–hydrogen plasma. The electrochemical properties of the N-PyC films were investigated using the ferri/ferro-cyanide and hexaamine ruthenium(III) chloride redox probes. Exceptional electron transfer properties were observed and quantified for the N-PyC compared to the as-grown films. X-ray photoelectron spectroscopy confirmed the presence of nitrogen in edge plane graphitic configurations and the surface of the N-PyC was investigated using scanning electron microscopy and atomic force microscopy. The excellent electrochemical performance of the N-PyC, in addition to its ease of preparation, renders this material ideal for applications in electrochemical sensing.
Co-reporter:Nanjundan Ashok Kumar, Hugo Nolan, Niall McEvoy, Ehsan Rezvani, Richard L. Doyle, Michael E. G. Lyons and Georg S. Duesberg
Journal of Materials Chemistry A 2013 - vol. 1(Issue 14) pp:NaN4435-4435
Publication Date(Web):2013/02/19
DOI:10.1039/C3TA10337D
An environmentally benign and scalable route for the production of gram scale quantities of nitrogen-doped graphene using a downstream microwave plasma source is reported. Simultaneous reduction and doping of graphene oxide is achieved and the process negates the need for high temperatures and toxic solvents associated with existing methods. This gas-phase low temperature process is completely dry and, thus, minimises re-aggregation of graphene flakes which is typically associated with liquid phase reduction methods. The resulting material has many potential uses, particularly in electrochemical energy.
Co-reporter:Sinéad Winters, Nina C. Berner, Rohit Mishra, Kim C. Dümbgen, Claudia Backes, Martin Hegner, Andreas Hirsch and Georg S. Duesberg
Chemical Communications 2015 - vol. 51(Issue 94) pp:NaN16781-16781
Publication Date(Web):2015/09/28
DOI:10.1039/C5CC06433C
An efficient, high-throughput method for the formation of densely packed molecular films on graphene is reported. The films exhibit high stability and remain intact during a subsequent derivatisation reaction, offering a versatile route for the non-covalent functionalisation of graphene.
