Imperial College London

ProfessorMaryRyan

Faculty of EngineeringDepartment of Materials

Vice-Dean (Research), Faculty of Engineering
 
 
 
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Contact

 

+44 (0)20 7594 6755m.p.ryan

 
 
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Location

 

B338Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

220 results found

Illy BN, Cruickshank AC, Da Campo R, Schumann S, Jones TS, Heutz SEM, McLachlan MA, McComb DW, Riley DJ, Ryan MPet 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.

Conference paper

Illy BN, Cruickshank AC, Schumann S, Campo RD, Jones TS, Heutz S, McLachlan MA, McComb DW, Riley DJ, Ryan MPet al., 2011, Electrodeposition of ZnO layers for photovoltaic applications: controlling film thickness and orientation, Journal of Materials Chemistry

Journal article

Cruickshank A, Tay S, Illy B, Dearden C, Jones TS, McLachlan MA, McComb DW, Riley DJ, Heutz S, Ryan MPet 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.

Journal article

Skinner SJ, Packer RJ, Bayliss RD, Illy B, Prestipino C, Ryan MPet al., 2011, Redox chemistry of the novel fast oxide ion conductor CeNbO4+d determined through an in-situ spectroscopic technique, 17th International Conference on Solid State Ionics, Publisher: ELSEVIER SCIENCE BV, Pages: 659-663, ISSN: 0167-2738

Conference paper

McLachlan MA, Rahman H, Illy B, McComb DW, Ryan MPet 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.

Journal article

Franklin JB, Zou B, Petrov P, McComb DW, Ryan MP, McLachlan MAet 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.

Journal article

Mclachlan MA, McComb DW, Ryan MP, Morozovska AN, Eliseev EA, Payzant EA, Jesse S, Seal4 K, Baddorf AP, Kalinin SVet 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

Journal article

Downing J, Ryan MP, Stingelin N, McLachlan MAet 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.

Journal article

Chater RJ, Corni I, Boccaccini AR, Ryan MPet al., 2011, Three-dimensional reconstruction of a nickel-alumina composite coating by FIB-SIMS, SURFACE AND INTERFACE ANALYSIS, Vol: 43, Pages: 492-494, ISSN: 0142-2421

Journal article

Woolley RJ, Illy BN, Ryan MP, Skinner SJet al., 2011, In situ determination of the nickel oxidation state in La2NiO4+delta and La4Ni3O10-delta using X-ray absorption near-edge structure, JOURNAL OF MATERIALS CHEMISTRY, Vol: 21, Pages: 18592-18596, ISSN: 0959-9428

Journal article

Schumann S, Campo RD, Illy B, Cruickshank AC, McLachlan MA, Ryan MP, Riley DJ, McComb DW, Jones TSet 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.

Journal article

Muller KH, Kulkarni J, Motskin M, Goode A, Winship P, Skepper JN, Ryan MP, Porter AEet al., 2010, pH-Dependent Toxicity of High Aspect Ratio ZnO Nanowires in Macrophages Due to Intracellular Dissolution, ACS NANO, Vol: 4, Pages: 6767-6779, ISSN: 1936-0851

Journal article

Pishbin F, Simchi A, Ryan MP, Boccaccini ARet al., 2010, A study of the electrophoretic deposition of Bioglass (R) suspensions using the Taguchi experimental design approach, 4th International Conference on Shaping of Advanced Ceramics, Publisher: ELSEVIER SCI LTD, Pages: 2963-2970, ISSN: 0955-2219

Conference paper

Fajardo S, Bastidas DM, Ryan MP, Criado M, McPhail DS, Bastidas JMet al., 2010, Low-nickel stainless steel passive film in simulated concrete pore solution: A SIMS study, APPLIED SURFACE SCIENCE, Vol: 256, Pages: 6139-6143, ISSN: 0169-4332

Journal article

Wang H, Mauthoor S, Din S, Gardener JA, Chang R, Warner M, Aeppli G, McComb DW, Ryan MP, Wu W, Fisher AJ, Stoneham M, Heutz Set al., 2010, Ultra long Copper Phthalocyanine Nanowires with New Crystal Structure and Broad Optical Absorption, ACS NANO, Vol: 4, Pages: 3921-3926, ISSN: 1936-0851

Journal article

Koblischka-Veneva A, Koblischka MR, Teng CL, Ryan MP, Hartmann U, Muecklich Fet al., 2010, EBSD analysis of electroplated magnetite thin films, 4th Joint European Magnetic Symposia (JEMS 08), Publisher: ELSEVIER SCIENCE BV, Pages: 1235-1238, ISSN: 0304-8853

Conference paper

Illy BN, Ingham B, Ryan MP, 2010, Effect of Supersaturation on the Growth of Zinc Oxide Nanostructured Films by Electrochemical Deposition, CRYSTAL GROWTH & DESIGN, Vol: 10, Pages: 1189-1193, ISSN: 1528-7483

Journal article

Ingham B, Hendy SC, Fong DD, Fuoss PH, Eastman JA, Lassesson A, Tee KC, Convers PY, Brown SA, Ryan MP, Toney MFet al., 2010, Synchrotron x-ray diffraction measurements of strain in metallic nanoparticles with oxide shells, JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 43, ISSN: 0022-3727

Journal article

Atienzar P, Ishwara T, Illy BN, Ryan MP, O'Regan BC, Durrant JR, Nelson Jet al., 2010, Control of Photocurrent Generation in Polymer/ZnO Nanorod Solar Cells by Using a Solution-Processed TiO2 Overlayer, JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Vol: 1, Pages: 708-713, ISSN: 1948-7185

Journal article

Soltis J, Krouse DP, Hodges S, Laycocki NJ, Zavadil KR, Virtanen S, Schmutz P, Ryan MPet al., 2010, Automated Analysis of Electrochemical Current Noise from Potentiostatic Conditioning of Passive Iron in Chloride-Containing Solutions, Symposium on Corrosion General Session held during the 216th Meeting of the Electrochemical-Society (ECS), Publisher: ELECTROCHEMICAL SOC INC, Pages: 157-176, ISSN: 1938-5862

Conference paper

Ingham B, Brady CDA, Burstein GT, Gaston N, Ryan MPet al., 2009, EXAFS Analysis of Electrocatalytic WC Materials, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 113, Pages: 17407-17410, ISSN: 1932-7447

Journal article

Corni I, Neumann N, Novak S, Koenig K, Veronesi P, Chen Q, Ryan MP, Boccaccini ARet al., 2009, Electrophoretic deposition of PEEK-nano alumina composite coatings on stainless steel, SURFACE & COATINGS TECHNOLOGY, Vol: 203, Pages: 1349-1359, ISSN: 0257-8972

Journal article

Zhu R, McLachlan MA, Reyntjen S, Tariq F, Ryan MPet al., 2009, Controlling the electrodeposition of mesoporous metals for nanoplasmonics, Nanoscale, Vol: 1, Pages: 355-359

Journal article

Xie F, Ryan M, Riley J, Mason Pet al., 2009, Investigation of homogeneous large surface area anodic alumina membrane synthesis, IEEE-NANO 2009. 9th IEEE Conference, Pages: 319-321

Conference paper

Ingham B, Toney MF, Hendy SC, Cox T, Fong DD, Eastman JA, Fuoss PH, Stevens KJ, Lassesson A, Brown SA, Ryan MPet al., 2008, Particle size effect of hydrogen-induced lattice expansion of palladium nanoclusters, PHYSICAL REVIEW B, Vol: 78, ISSN: 2469-9950

Journal article

Zhu R, McLachlan MA, McComb DW, Ryan MPet 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.

Conference paper

Ingham B, Illy BN, Toney MF, Howdyshell ML, Ryan MPet al., 2008, In situ synchrotron X-ray diffraction experiments on electrochemically deposited ZnO nanostructures, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 112, Pages: 14863-14866, ISSN: 1932-7447

Journal article

Boccaccini AR, Grimes RW, Ryan MP, Skinner SJet al., 2008, Rees Rawlings special issue, JOURNAL OF MATERIALS SCIENCE, Vol: 43, Pages: 3989-3989, ISSN: 0022-2461

Journal article

Ingham B, Illy BN, Ryan MP, 2008, In situ synchrotron studies of ZnO nanostructures during electrochemical deposition, 3rd International Conference on Advanced Materials and Nanotechnology, Publisher: ELSEVIER SCIENCE BV, Pages: 455-458, ISSN: 1567-1739

Conference paper

Ingham B, Illy BN, Ryan MP, 2008, Direct observation of distinct nucleation and growth processes in electrochemically deposited ZnO nanostructures using in situ XANES, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 112, Pages: 2820-2824, ISSN: 1932-7447

Journal article

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