Publications
133 results found
Hota MK, Caraveo-Frescas JA, McLachlan MA, et al., 2014, Electroforming-free resistive switching memory effect in transparent <i>p</i>-type tin monoxide, APPLIED PHYSICS LETTERS, Vol: 104, ISSN: 0003-6951
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- Citations: 27
Beesley DJ, Semple J, Krishnan Jagadamma L, et al., 2014, Sub-15-nm patterning of asymmetric metal electrodes and devices by adhesion lithography, Nat Commun, Vol: 5
Coplanar electrodes formed from asymmetric metals separated on the nanometre length scale are essential elements of nanoscale photonic and electronic devices. Existing fabrication methods typically involve electron-beam lithography—a technique that enables high fidelity patterning but suffers from significant limitations in terms of low throughput, poor scalability to large areas and restrictive choice of substrate and electrode materials. Here, we describe a versatile method for the rapid fabrication of asymmetric nanogap electrodes that exploits the ability of selected self-assembled monolayers to attach conformally to a prepatterned metal layer and thereby weaken adhesion to a subsequently deposited metal film. The method may be carried out under ambient conditions using simple equipment and a minimum of processing steps, enabling the rapid fabrication of nanogap electrodes and optoelectronic devices with aspect ratios in excess of 100,000.
Franklin JB, Gilchrist JB, Downing JM, et al., 2014, Transparent conducting oxide top contacts for organic electronics, JOURNAL OF MATERIALS CHEMISTRY C, Vol: 2, Pages: 84-89, ISSN: 2050-7526
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- Citations: 12
Marshall J, Hooton J, Han Y, et al., 2014, Polythiophenes with vinylene linked <i>ortho</i>, <i>meta</i> and <i>para</i>-carborane sidechains, POLYMER CHEMISTRY, Vol: 5, Pages: 6190-6199, ISSN: 1759-9954
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- Citations: 19
Koch FPV, Rivnay J, Foster S, et al., 2013, The impact of molecular weight on microstructure and charge transport in semicrystalline polymer Semiconductors poly(3-hexylthiophene), a model study, PROGRESS IN POLYMER SCIENCE, Vol: 38, Pages: 1978-1989, ISSN: 0079-6700
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- Citations: 238
Wood S, Franklin JB, Stavrinou PN, et al., 2013, Interfacial molecular order of conjugated polymer in P3HT:ZnO bilayer photovoltaics and its impact on device performance, APPLIED PHYSICS LETTERS, Vol: 103, ISSN: 0003-6951
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- Citations: 12
Lin Y-H, Faber H, Zhao K, et al., 2013, High-Performance ZnO Transistors Processed Via an Aqueous Carbon-Free Metal Oxide Precursor Route at Temperatures Between 80-180 °C (vol 25, pg 4340, 2013), ADVANCED MATERIALS, Vol: 25, Pages: 4689-4689, ISSN: 0935-9648
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- Citations: 3
Mallinson CF, Gray BM, Hector AL, et al., 2013, Templated non-oxide sol-gel preparation of well-ordered macroporous (inverse opal) Ta3N5 films., Inorganic Chemistry, Vol: 52, Pages: 9994-9999, ISSN: 1520-510X
Reactions of Ta(NMe2)5 and n-propylamine are shown to be an effective system for sol-gel processing of Ta3N5. Ordered macroporous films of Ta3N5 on silica substrates have been prepared by infiltration of such a sol into close-packed sacrificial templates of cross-linked 500 nm polystyrene spheres followed by pyrolysis under ammonia to remove the template and crystallize the Ta3N5. Templates with long-range order were produced by controlled humidity evaporation. Pyrolysis of a sol-infiltrated template at 600 °C removes the polystyrene but does not crystallize Ta3N5, and X-ray diffraction shows nanocrystalline TaN plus amorphous material. Heating at 700 °C crystallizes Ta3N5 while retaining a high degree of pore ordering, whereas at 800 °C porous films with a complete loss of order are obtained.
Lin Y-H, Faber H, Zhao K, et al., 2013, High-Performance ZnO Transistors Processed Via an Aqueous Carbon-Free Metal Oxide Precursor Route at Temperatures Between 80-180 °C, ADVANCED MATERIALS, Vol: 25, Pages: 4340-4346, ISSN: 0935-9648
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- Citations: 155
Downing JM, Ryan MP, McLachlan MA, 2013, Hydrothermal growth of ZnO nanorods: The role of KCl in controlling rod morphology, Thin Solid Films
The role of potassium chloride (KCl) in controlling ZnO nanorod morphology of large area thin films prepared by hydrothermal growth has been extensively investigated. The influence of KCl and growth time on the orientation, morphology and microstructure of the nanorod arrays has been studied with systematic changes in the length, width, density and termination of the nanorods observed. Such changes are attributed to stabilization of the high-energy (002) nanorod surface by the KCl. At low KCl concentrations (< 100 mM) c-axis growth i.e. perpendicular to the polar surface, dominates, leading to nanorods with increased length over the control sample (0 mM KCl). At higher concentrations (> 100 mM) stabilization of the high-energy surface by KCl occurs and planar (002) facets are observed accompanied by increased lateral (100) growth, at the highest KCl concentrations near coalesced (002) terminated rods are observed. Additionally we correlate the KCl concentration with the uniformity of the nanorod arrays; a decrease in polydispersity with increased KCl concentration is observed. The vertical alignment of nanorod arrays was studied using X-ray diffraction, it was found that this parameter increases as growth time and KCl concentration are increased. We propose that the increase in vertical alignment is a result of nanorod–nanorod interactions during the early stages of growth.
Pattanasattayavong P, Thomas S, Adamopoulos G, et al., 2013, <i>p</i>-channel thin-film transistors based on spray-coated Cu<sub>2</sub>O films, APPLIED PHYSICS LETTERS, Vol: 102, ISSN: 0003-6951
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- Citations: 93
Franklin JB, Downing JM, Giuliani F, et al., 2012, Building on Soft Foundations – New Possibilities for Controlling Hybrid Photovoltaic Architectures, Advanced Energy Materials
Here we outline a methodology for the deposition of a highly crystalline transparent conductive metal oxide (ZnO) onto a functionalised organic thin film poly (3-hexylthiophene, P3HT) without degradation of the microstructural, optical or electronic properties of the organic layer. To confirm the absence of damage we have assembled a simple bilayer photovoltaic (PV) device. The processing methodology has enabled us to demonstrate hybrid photovoltaic (h-PV) device formation in the conventional architecture for the first time. The compatibility of this novel low temperature processing route with π-conjugated molecular materials has tremendous potential for applications including electron accepting layers and optical spacers in organic PVs and light emitting diodes, as transparent electrodes and all future devices reliant on flexible substrates.
Fei Z, Kim Y, Smith J, et al., 2012, Comparative Optoelectronic Study between Copolymers of Peripherally Alkylated Dithienosilole and Dithienogermole, Macromolecules
Here we report a simple methodology for the synthesis of dithienosilole and dithienogermole monomers in which the necessary solubilizing long chain alkyl groups are incorporated into the peripheral 3,5-positions of the fused ring. We report four novel monomers in which methyl or butyl groups are attached to the bridging Si and Ge atom. Copolymers with bithiophene were synthesized by a Stille polymerization in high molecular weight. We report the optical, electrical, electrochemical and morphological properties of the resulting polymers. We find that the nature of the bridging heteroatom (Si or Ge) has only a minor influence on these properties, whereas the nature of the alkyl chain attached to the bridging atom is found to have a much larger effect.
McLachlan MA, Rahman H, Illy B, et al., 2011, Electrochemical deposition of ordered macroporous ZnO on transparent conducting electrodes, Materials Chemistry and Physics, Pages: 343-348
Large area macroporous zinc oxide (ZnO) films have been prepared by colloidal crystal templating on to transparent conducting oxide (TCO) substrates using an electrochemical deposition technique. Characterisation by scanning electron microscopy (SEM) reveals changes in the microstructure of the ZnO films as the template diameter and deposition potential are varied. Analysis by X-ray diffraction (XRD) and UV-Vis spectroscopy show that the structural variations do not influence the inherent properties of the ZnO. We attribute the observed microsturctural differences to variations in growth kinetics in response to the applied deposition potential and solution transport phenomena that are controlled by the template dimensions. The optical properties of the structures exhibit two distinct features, originating from the optical bandgap of the ZnO and the photonic band gap of the ordered macroporous structure.
Illy BN, Cruickshank AC, Schumann S, et al., 2011, Electrodeposition of ZnO layers for photovoltaic applications: controlling film thickness and orientation, Journal of Materials Chemistry
Illy BN, Cruickshank AC, Da Campo R, et al., 2011, Electrodeposition of ultrathin ZnO buffer layers with controllable orientation for photovoltaic applications, ISSN: 0065-7727
ZnO is one of the most promising materials for applications in nanotechnology due to its large band gap and high electron mobility. A large amount of work has focused on the study of nanostructured ZnO. However, two dimensional transparent compact layers are also of great interest as transparent conductive oxides in optoelectronic devices. Compact ZnO layers are usually deposited by methods which are generally costly thus significantly limiting their potential application. Electrodeposition is a low cost alternative, offering a high degree of control on the characteristics. In this work the effects of the deposition parameters on the film characteristics have been studied in order to fabricate the thinnest electrodeposited films ever reported and to tune the crystallographic orientation. Incorporation of the layer into an organic ZnO/P3HT:PCBM solar cell is used to demonstrate how a careful control of the orientation can dramatically improve the photovoltaic device efficiency.
Cruickshank A, Tay S, Illy B, et al., 2011, Electrodeposition of ZnO Nanostructures on Molecular Thin Films, Chemistry of Materials, Vol: 23, Pages: 3863-3870, ISSN: 1520-5002
Electrodeposition of highly crystalline ZnO nanostructures directly onto copper phthalocyanine and pentacene thin films, from aqueous solutions containing zinc nitrate and dissolved oxygen, has been successfully demonstrated for the first time using a two-step electrochemical deposition process. Importantly, surface activation of the molecular thin film substrates by depositing a thin layer of ZnO nanoparticles at high cathodic overpotentials prior to film growth was found to be crucial for achieving a dense coverage of ZnO nanostructures with uniform morphology. The mechanism for ZnO deposition via electroreduction of hydroxide precursor species (oxygen and NO3– ions) at the organic-electrolyte interface was shown to be analogous to that reported for conventional inorganic and metal electrodes. Comparison of cathodic current density-time curves, measured during deposition, with film orientation and morphology revealed that the cathodic current density and number of nucleation sites are key factors in determining the characteristics of ZnO film growth on organic substrates. Significantly, the CuPc and pentacene films are not damaged or degraded during this process.
Franklin JB, Zou B, Petrov P, et al., 2011, Optimised Pulsed Laser Deposition of ZnO Thin Films on Transparent Conducting Substrates, Journal of Materials Chemistry, Vol: 21, Pages: 8178-8182
The growth of polycrystalline zinc oxide (ZnO) thin films by pulsed laser deposition (PLD) on indium tin oxide (ITO) is reported. For the first time the influence of deposition temperature over an extended range (50 - 650 °C) is investigated on ITO. We describe the role of temperature on the optical and crystalline properties of the deposited films, of 120-250 nm thickness. Additionally, the effect of the background oxygen pressure is reported. Under all of the deposition conditions highly textured c-axis oriented ZnO, transparent (> 85%) and low roughness (RMS < 10 nm) films are formed. Growth temperatures ≥ 450 ˚C lead to the highest degree of crystallinity and film quality with measured full width half maximum (FWHM) of X-ray diffraction (XRD) peaks as small as 0.14 ˚2θ. XRD measurements of films grown at < 350 °C show a shift in the (002) diffraction peak to lower 2θ values, indicating that the deposited films are oxygen deficient. Increasing the oxygen pressure results in the preparation of stoichiometric films at temperatures as low as 50 °C. We demonstrate that in addition to forming high quality ZnO, the optical and electronic properties of ITO can be preserved, even at high temperature, presenting a methodology for preparing highly crystalline ZnO on ITO over a temperature window significantly larger than that of previous literature reports. Furthermore, the low temperature processing opens up the possibility of deposition on a wide range of substrates, especially those unsuitable for exposure to high temperatures.
Adamopoulos G, Stuart T, Bradley DDC, et al., 2011, High-mobility low-voltage ZnO transistors based on ZrO2 high-kdielectric grown by spray pyrolysis in ambient air, Advanced Materials, 2011, Vol: 23
Adamopoulos G, Thomas S, Bradley DDC, et al., 2011, Low-voltage ZnO thin-film transistors based on Y2O3 and Al2O3 high-kdielectrics deposited by spray pyrolysis in air, Applied Physics letters, 2011, Vol: 98
We report the application of ambient spray pyrolysis for the deposition of high-k polycrystalline Y2O3 and amorphous Al2O3 dielectrics and their use in low-voltage ZnO thin-film transistors. The films are studied by means of atomic force microscopy, UV-visible absorption spectroscopy, impedance spectroscopy, and field-effect measurements. ZnO transistors based on spray pyrolysed Y2O3 and Al2O3 dielectrics show low leakage currents, low voltage 6 V , and hysteresis-free operation with a maximum electron mobility of 34 cm2 / V s and current on/off ratio on the order of 105. This work is a significant step toward high-performance oxide electronics manufactured using simple and scalable processing methods
Mclachlan MA, McComb DW, Ryan MP, et al., 2011, Probing local and global ferroelectric phase stability and polarization switching in ordered macroporous PZT, Advanced Functional Materials, Vol: 21, Pages: 941-947
We describe the characterization, ferroelectric phase stability and polarization switching in strain-free assemblies of PbZr0.3Ti0.7O3 (PZT) nanostructures. The 3-dimensionally ordered macroporous structures present uniquely large areas and volumes of PZT where the microstructure is spatially modulated and the composition is homogeneous. Variable temperature powder X-ray diffraction (XRD) studies show that the global structure is crystalline and tetragonal at room temperature and undergoes a reversible tetragonal to cubic phase transition on heating/cooling. The measured phase-transition temperature is 50 – 60 °C lower than bulk PZT of the same composition. The local ferroelectric properties were assessed using piezoresponse force spectroscopy that reveal an enhanced piezoresponse from the nanostructured films and demonstrate that the switching polarization can be spatially mapped across these structures. An enhanced piezoresponse is observed in the nanostructured films which we attribute to the formation of strain free films, thus for the first time we are able to assess the effects of crystallite-size independently of internal stress. Corresponding polarization distributions have been calculated for the bulk and nanostructured materials using a direct variational method and Landau-Ginzburg-Devonshire (LGD) theory. By correlating local and global characterisation techniques we have for the first time unambiguously demonstrated the formation of tetragonal and ferroelectric PZT in large volume nanostructured architectures. With the wide range of materials available that can be formed into such controlled architectures we conclude that this study opens a pathway for the effective studies of nanoscale ferroelectrics in uniquely large volumes
McLachlan MA, McComb DW, Ryan MP, et al., 2011, Ferroelectric Materials: Probing Local and Global Ferroelectric Phase Stability and Polarization Switching in Ordered Macroporous PZT (Adv. Funct. Mater. 5/2011), Advanced Functional Materials, Vol: 21, Pages: 802-802, ISSN: 1616-301X
<jats:title>Abstract</jats:title><jats:p>We describe the characterization, ferroelectric phase stability and polarization switching in strain‐free assemblies of PbZr<jats:sub>0.3</jats:sub>Ti<jats:sub>0.7</jats:sub>O<jats:sub>3</jats:sub> (PZT) nanostructures. The 3‐dimensionally ordered macroporous structures present uniquely large areas and volumes of PZT where the microstructure is spatially modulated and the composition is homogeneous. Variable temperature powder X‐ray diffraction (XRD) studies show that the global structure is crystalline and tetragonal at room temperature and undergoes a reversible tetragonal to cubic phase transition on heating/cooling. The measured phase‐transition temperature is 50–60 °C lower than bulk PZT of the same composition. The local ferroelectric properties were assessed using piezoresponse force spectroscopy that reveal an enhanced piezoresponse from the nanostructured films and demonstrate that the switching polarization can be spatially mapped across these structures. An enhanced piezoresponse is observed in the nanostructured films which we attribute to the formation of strain free films, thus for the first time we are able to assess the effects of crystallite‐size independently of internal stress. Corresponding polarization distributions have been calculated for the bulk and nanostructured materials using a direct variational method and Landau‐Ginzburg‐Devonshire (LGD) theory. By correlating local and global characterization techniques we have for the first time unambiguously demonstrated the formation of tetragonal <jats:italic>and</jats:italic> ferroelectric PZT in large volume nanostructured architectures. With the wide range of materials available that can be formed into such controlled architectures we conclude that this study opens a pathway for the effective studies of nanoscale ferroelectrics in uniquely large volumes.</jats:p>
Downing J, Ryan MP, Stingelin N, et al., 2011, Solution Processed Hybrid Photovoltaics - The Preparation of a Standard ZnO Template, Journal of Photonics for Energy, 2011, Vol: 1
The formation of a well-defined, reproducible ZnO nanorod scaffolds for hybrid photovoltaic (h-PV) applications has been investigated. A standard hydrothermal growth method was used and the influence of chemical additions in controlling length, width, density and orientation was studied. The nanostructures prepared have been characterised by scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy in addition to measurement of the wetting behaviour. A standard procedure for the production of vertically orientated nanorods with a narrow size distribution, high areal density and good wettability in aqueous solutions is presented.
Schumann S, Campo RD, Illy B, et al., 2011, Inverted organic photovoltaic devices with high efficiency and stability based on metal oxide charge extraction layers, Journal of Materials Chemistry, 2011, Pages: 2381-2386
A substantial increase in device performance and operational stability in solution processed inverted bulk heterojunction (BHJ) organic photovoltaic devices (OPV) is demonstrated by introducing a zinc oxide (ZnO) interlayer between the electron collecting bottom electrode and the photoactive blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM). The structure and morphology of the dense, planar ZnO layers were controlled either by electro-deposition or spray pyrolysis techniques. Metal oxide sandwich OPV devices based on the photoactive blend on an electro-deposited ZnO interlayer with a (100) preferential crystal orientation, and using a tungsten oxide (WOx) interlayer on the opposite electrode, resulted in a remarkable increase in power conversion efficiency with a value of 4.91% under AM1.5 illumination and an external quantum efficiency of 74%. Electro-deposition of the ZnO at low temperature proved to be the most promising method for forming the ZnO interlayers, allowing the highest control of film structure and morphology, as well as leading to significantly improved device efficiency and stability.
Thomson NR, McLachlan MA, Bower CL, et al., 2009, Formation of Patterned Arrays of Polystyrene Colloidal Crystal Structures on Flexible Functional Substrates, Langmuir
Zhu R, McLachlan MA, Reyntjen S, et al., 2009, Controlling the electrodeposition of mesoporous metals for nanoplasmonics, Nanoscale, Vol: 1, Pages: 355-359
Zhu R, McLachlan MA, McComb DW, et al., 2008, Electrochemically grown metallic inverse opals, Pages: 1-6, ISSN: 1938-5862
3-dimensionally ordered macroporous Cu and Ag were grown using electrodeposition coupled with a colloidal template. The films are homogenous and uniform over a large scale. Optical characterization has confirmed their three-dimensional periodicity and indicated the inverse structures have stop band properties in the visible wavelength range consistent with variation in the effective refractive index of the films. © The Electrochemical Society.
McLachlan MA, McComb DW, Ying A, et al., 2008, Engineered Nanocomposites for Solid Oxide Fuel Cells By Colloidal Crystal Templating
Berhanu S, McLachlan MA, McComb DW, et al., 2008, Colloidal Crystals as Nanostructured Templates for Organic Solar Cells, Conference on Organic Photovoltaics IX, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
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- Citations: 1
McLachlan MA, Barron CCA, Johnson NP, et al., 2008, Preparation of large area three-dimensionally ordered macroporous thin films by confined infiltration and crystallisation, Journal of Crystal Growth, Vol: 310, Pages: 2644-2646
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