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The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. A high density of silicon nanowires for solar cell applications was fabricated on a single crystalline silicon wafer, using low eutectic temperature metal catalysts, namely, gallium, indium, tin, and bismuth. The use of silicon nanowires is exploited for light trapping with an aim to enhance the efficiency of solar cells. Additionally, we have optimized the deposition parameters so that there is merely deposition of amorphous silicon along with the growth of silicon nanowires. Thus, it may improve the stability of silicon-based solar cells. The different catalysts used are extensively discussed with experimental results indicating stable growth and highly efficient silicon nanowires for photovoltaic applications. To test the stability, we measured the open-circuit voltage for four hours and the change in voltage was ±0.05 V. The fabrication of all-crystalline silicon solar cells was demonstrated using the conventional mature industrial manufacturing process that is presently used for the amorphous silicon solar cells. To summarize, this research compares various post-transition metals as a catalyst for the growth of nanowires discussing their properties, and such silicon nanowires can be utilized in several other applications not only limited to photovoltaic research.

Farmer profit can be increased and air quality improved

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Effect of plasma treatment on transparent conductive oxides (TCOs) including indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO) and aluminium-doped zinc oxide (AZO) are discussed. Stability of electrical and optical properties of TCOs, when exposed to plasma species generated from gases such as hydrogen and silane, are studied extensively. ITO and FTO thin films are unstable and reduce to their counterparts such as Indium and Tin when subjected to plasma. On the other hand, AZO is not only stable but also shows superior electrical and optical properties. The stability of AZO makes it suitable for electronic applications, such as solar cells and transistors that are fabricated under plasma environment. TCOs exposed to plasma with different fabrication parameters are used in the fabrication of silicon nanowire solar cells. The performance of solar cells, which is mired by the plasma, fabricated on ITO and FTO is discussed with respect to plasma exposure parameters while showing the advantages of using chemically stable AZO as an ideal TCO for solar cells. Additionally, in-situ diagnostic tool (optical emission spectroscopy) is used to monitor the deposition process and damage caused to TCOs.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Selection of a material that serves multiple purposes is always beneficial for any electronic device including solar cells. This study investigates nickel oxide (NiO) as a multipurpose material to overcome the potential issues observed in traditional solar cells. A proof-of concept device is fabricated to understand the efficient hole transport from NiO while blocking electrons as determined by I-V measurements showing suppression of dark current and enhancement in the power conversion from the solar cell. Enhanced surface defects in the silicon nanowires (SiNWs) leading to the poor carrier collection is possible to be improved by the selection of wide bandgap metal-oxides that show high band offset for one carrier (electron/hole) while negligible band offset for another carrier (hole/electron) is discussed. Furthermore, Fermi level de-pinning for NiO sandwiched between different metal electrodes and SiNWs, signifying that the selection of appropriate metal electrodes is another key factor in improving the efficiency of solar cells; which is experimentally studied in this work. As fabricated solar cells in this work do not use high temperature diffused P[sbnd]N junction to separate the charge carriers neither toxic gases for doping SiNWs.

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. In this study, hydrogenated amorphous carbon (a-C:H) films are investigated for electronic applications as an insulating layer. a-C:H films were deposited using radio frequency-Plasma enhanced chemical vapour deposition (RF-PECVD) technique at room temperature. For the first time, the properties of a-C:H films as a function of annealing temperature is investigated, with a focus on their electrical and optical properties. This study shows that a-C:H films are stable up to 450ºC. This investigation will facilitate the use of a-C:H films as an insulating layer where the semiconductor active layers are deposited at higher temperatures (e.g. amorphous silicon deposited around 300ºC for thin film transistor TFTs). In addition to understanding the electrical and optical properties of annealed a-C:H films, we have further explored and studied its suitability in Flash-type memory devices. Various forms of diamond-like carbon are considered to have a high chemical resistance; no extensive data are available in the literature on this subject. The stability of a-C: H thin films with various reactive chemicals, commonly used in organic/printable electronic devices, is also investigated in this work. The findings may provide opportunities for adoption/integration of a-C:H in hybrid organic-inorganic electronic devices.

This is an Open Access article. Intensive research is currently underway to exploit the highly interesting properties of nano-bits (“nano-sized particles and molecules”) for optical, electronic and other applications. The basis of these unique properties is the small-size of these structures which result in quantum mechanical phenomena and interesting surface properties. The small molecules and/or nano-particles are selected in such a way so that it can create an internal electric in the nano-composite. We define a nanocomposite is an admixture of small molecules and/or nano-particles and a polymer. We have demonstrated the internal electric field in our devices, made from nano-bits (nano-particles and/or molecules) and insulating materials, can contribute to the electrical bistability i.e. two conductive states.

White button mushroom accounts for 35–45% of the total mushroom produced in the world. Modified atmosphere packaging or MAP is a technology that, along with low temperature storage, helps in extending the shelf life and maintenance of quality of the produce packaged in polymeric films. The present study mathematically modeled the various transport processes associated with the mushroom under MAP at 15C and 75% relative humidity (RH) using the enzyme kinetics approach. Low density polyethylene (LDPE), polypropylene (PP) and oriented polypropylene (OPP) films were used to pack the mushroom. Numerical solutions to the transient state equations were programed in a computer programing language to predict the in-pack gaseous partial pressures at any instant of time. The model was experimentally validated, and a simple qualitative tool based upon optimum whiteness of mushroom was developed using the predictions to determine the safe period of storage. The predicted and experimental in-pack partial pressures of O2 and CO2 were in fair agreement with each other. In the OPP film packages, the O2 and CO2 levels stabilized around 6.87 and 12.93 kPa, respectively. Whereas, O2 levels decreased drastically in LDPE and PP film packages. A combination of predicted in-pack environment in all the film packages, storage time and whiteness of mushroom led to the conclusion that mushrooms can be stored safely for 32, 44 and 108 h in the gaseous environment available in the LDPE, PP and OPP film packages, respectively. PRACTICAL APPLICATIONS The empirical approach followed in this study through assimilation of various transient state in-pack variables with a single qualitative attribute of mushroom can serve as a measure of assessment of the mushroom's safe storage period under modified atmosphere packaging. Further, the mathematical approach suggested in this study can also serve as a benchmark for its application to other fruits and vegetables, taking into consideration their respective limiting qualitative characteristics. Thus, the results detailed in the study can be easily applied for their direct practical application during storage as well as for further academic exercises.

The capacitance-voltage (C-V) characteristics of thin films of ZrO2 deposited by thermal metal-organic chemical vapour deposition (MOCVD) have been analyzed. The films were grown at three different temperatures (500, 550 and 600 ºC) and 1 mbar pressure from a novel monomeric zirconium amide-guanidinate complex [Zr(NEtMe)2(guanidinate)2]. The true capacitance was determined from measurements made at different frequencies in order to account for the series and shunt parasitic resistances during C-V measurements. Films grown at 500 and 550 ºC showed no hysteresis while those grown at 600 ºC exhibited a very small hysteresis window ≈0.16 V for O2 flow of 100 sccm and ≈0.19 V for 50 sccm O2 flow. A very small voltage shift is also obtained for the device under 10 hr voltage stress. These preliminary in-depth electrical results suggest that quality ZrO2 can be grown from the novel [Zr(NEtMe)2(guanidinate)2] complex precursor paving the way for their use as future gate dielectrics.

The evaluation of transient-state in-pack respiration rates for oxygen (O2) consumption and carbon dioxide (CO2) evolution at any instant of time for a commodity packaged in polymeric film packages and kept under modified atmosphere (MA) for long-term storage requires regular analysis of the in-pack partial pressures of O2 and CO2. Enzyme kinetic theory has been observed to make near-accurate predictions of the respiration rates of many commodities under MA. This approach was followed to evaluate the respiration rates of the ‘button’ mushroom, packaged in low-density polyethylene (LDPE), polypropylene (PP) and oriented polypropylene (OPP) film packages at any instant of time, utilising the produce, package and the environmental parameters. The respiration model parameters under the specified environmental conditions of 15 °C and 75% relative humidity (RH) were evaluated using multiple regression analysis and were utilised to know the predicted rates of respiration for O2 consumption and CO2 evolution. The experimental in-pack partial pressures of O2 and CO2 under all the packaging treatments agreed fairly well with the predicted values for a storage period of 96 h. The predicted rates of respiration dropped drastically in LDPE and PP film packages, but arrived to near-constant levels (115 and 110 ml kg−1 h−1 for the O2 consumption and CO2 evolution, respectively) in the OPP film packages after 36 h, indicating the condition of gaseous equilibrium in these packages. Results of the study confirm that the enzyme kinetics approach can be used to predict the respiration rates of any commodity under MA in polymeric films.

Nickel oxide has been investigated for several potential applications, namely, ultraviolet detectors, electro chromic devices, displays, diodes for light emitting, transparent conductive electrode, and optoelectronic devices. These applications require an in depth analysis of nickel oxide prior to its exploration in aforementioned devices. Optical properties of materials were investigated by depositing thin film of nickel oxide on different substrates in order to understand if the choice of substrate can have effect on deducing various optical parameters and can lead to wrong conclusions. In view of this, we have investigated optical properties of nickel oxide deposited on different substrates (glass, transparent plastic, sapphire, potassium bromide, and calcium fluoride).

In this work, we demonstrate a hybrid silicon-organic nanocrystal floating gate memory device combining organic insulating materials, metal nanoparticles and Si MOSFET. The nanocrystals were organically passivated gold nanoparticles (Au-nps) forming a monolayer which was deposited by Langmuir–Blodgett (LB) technique. The FET device is fabricated on a Silicon-on-Insulator (SOI) substrate using conventional silicon processing. The nanoparticle layer is separated from the channel area of the FET with a 5 nm thermal SiO2 film and is isolated from the Al gate contact with a LB-deposited organic insulator layer. The memory effect is tested by means of threshold voltage shift measurements under different program/erase pulses. The nanocrystals can be charged either from the channel through the thermal oxide layer or from the gate through the organic insulator depending on the pulse applied pulse characteristics.

From the past several years, there have been numerous studies that describe the morphology of teeth, including mandibular first molars. This tooth presents a high rate of intercanals and anastomosis, mainly in the apical 5 mm, which presents a clinical challenge in terms of cleaning and disinfection. A missed canal can lead to failure of endodontic therapy. Therefore every effort must be made to locate additional canals if any. This case report shows a variation in conventional anatomy in mandibular first molars.

Deposition of gate insulator in the arsenic-based compound semiconductors (such as GaAs, AlGaAs), always causes stoichiometric changes in these materials. The deposition of any materials above 350 °C results in the segregation of As at the surface of the semiconductor, which deteriorates the metal-insulator field effect transistor properties. a-C:H can be deposited at room temperature and hence the effect of temperature on arsenic segregation can be eliminated. This work investigates the use of a-C:H as a gate insulator in arsenic-based compound semiconductors.

In this paper, a non-volatile memory device based on a blend of metal oxides (Known as NiO) and polymer has been investigated. These devices have shown to display memory effects; a marked difference in electrical conductivity between the ‘on’ and ‘off’ states. However, the exact mechanism under-pinning these two conductivities states are not very clear. The structures used in investigation are metal-admixture-metal (MAM) and metal-insulator-semiconductor (MIS) devices. Also, glass and p-types silicon (100 orientations) with a pre-prepared Ohmic back contact were used for the MAM and MIS substrates respectively. This work will address some of the questions in regard to the electrical bistability shown by polymer memory devices.

In the recent years a notable progress in the miniaturisation of electronic devices has been achieved in which the main component that has shown great interest is electronic memory. However, miniaturisation is reaching its limit. Alternative materials, manufacturing equipment and architectures for the storage devices are considered. In this work, an investigation on the suitability of silicon nanowires as the charge storage medium in two-terminal non-volatile memory devices is presented. Silicon nanostructures have attracted attention due to their small size, interesting properties and their potential integration into electronic devices. The two-terminal memory devices presented in this work, have a simple structure of silicon nanowires sandwiched between dielectric layers (silicon nitride) on glass substrate with thermally evaporated aluminium bottom and top contacts. The silicon nanostructures and the dielectric layer were deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) technique. The electrical behaviour of the memory cell was examined by Current-Voltage (I-V), data retention time (Current-time) and write-read-erase-read measurements. Metal-Insulator-Semiconductor (MIS) structures were also prepared for further analysis. The same silicon nanowires were embedded into the MIS capacitors and Capacitance-Voltage (C-V) analysis was conducted. Strong I-V and C-V hysteresis as well as an electrical bistability were detected. The memory effect is observed by this electrical bistability of the device that was able to switch between high and low conductivity states.

This paper represents the lowest growth temperature for silicon nano-wires (SiNWs) via a vapour-liquid–solid method, which has ever been reported in the literature. The nano-wires were grown using plasma-enhanced chemical vapour deposition technique at temperatures as low as 150°C using gallium as the catalyst. This study investigates the structure and the size of the grown silicon nano-structure as functions of growth temperature and catalyst layer thickness. Moreover, the choice of the growth temperature determines the thickness of the catalyst layer to be used. The electrical and optical characteristics of the nano-wires were tested by incorporating them in photovoltaic solar cells, two terminal bistable memory devices and Schottky diode. With further optimisation of the growth parameters, SiNWs, grown by our method, have promising future for incorporation into high performance electronic and optical devices.

In order to investigate the performance of ZnO-based thin film transistors (ZnO-TFTs), we fabricate devices using amorphous hafnium dioxide (HfO2) high-k dielectrics. Sputtered ZnO was used as the active channel layer, and aluminium source/drain electrodes were deposited by thermal evaporation, and the HfO2 high-k dielectrics are deposited by metal-organic chemical vapour deposition (MOCVD). The ZnO-TFTs with high-k HfO2 gate insulators exhibit good performance metrics and effective channel mobility which is appreciably higher in comparison to SiO2-based ZnO TFTs fabricated under similar conditions. The average channel mobility, turn-on voltage, on-off current ratio and subthreshold swing of the high-k TFTs are 31.2 cm2V-1s-1, -4.7 V, ~103, and 2.4 V/dec respectively. We compared the characteristics of a typical device consisting of HfO2 to those of a device consisting of thermally grown SiO2 to examine their potential for use as high-k dielectrics in future TFT devices.

Organic photovoltaic devices offer a potentially cheap source of electrical power due to the relative ease of processing compared to silicon devices. Over the last decade the efficiency of these devices has improved significantly and the best devices are currently have >6% power conversion efficiency and ~100% quantum efficiency.A novel blend of ferroelectric nanostructures, poly(3-hexylthiophene) (P3HT) and [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) has been used to fabricate hybrid organic and inorganic photovoltaic devices. These devices comprise a glass substrate coated with indium tin oxide (ITO) and an layer of PEDOT:PSS to form the first electrode. The active layer was deposited by spin coating and finally metallic top contacts have been added by thermal evaporation. The devices were characterized using standard current-voltage (IV) measurements under illuminated and dark conditions using an AM1.5 solar simulator and a source-voltage device and the results indicate a difference in efficiency compared to similar devices fabricated at the same time without the novel nanostructures. Additional UV-Vis measurements were used to determine the absorption characteristics of the active layers. The initial results suggest an improvement in the absorption of light in the visible region and higher open circuit voltages and short circuit currents compared to P3HT/PCBM alone.

For the last a few decades the interest in using organic materials in electronic applications (light emitting diodes, field effect transistors, solar cells, etc) has increased rapidly. Recently, organic materials have also been used to realise electronic memory devices. These devices show two electrical conductance states (“high” and “low”) when voltage is applied. The memory effect in these devices with simple structure based on a thin film of nano-sized particles and/or small molecules embedded in an organic layer was demonstrated. This work investigates organic memory devices based on organic materials–blend between small organic molecules (TTF and TCNE) and polymer (PVAc).

An in-depth study of the structural and electrical properties of silicon (Si) films deposited by a novel low temperature technique at temperatures less than 400°C in a 13.56 MHz RF PECVD reactor is reported. The method is based on substrates having to undergo some initial preparatory steps (IPS) before the deposition of Si films in the PECVD chamber. The optical band gap of Si films deposited using this novel technique narrowed to 1.25 eV from 1.78 eV using the traditional a-Si:H deposition recipe. No annealing of any form was performed on the films to attain this band gap. Furthermore, photosensitivities for these films under various deposition conditions were of order 100 compared to 104 for a-Si:H films deposited under like conditions. Using metal-insulator-semiconductor devices, the Si films grown by this novel technique exhibit charge storage and memory behaviour unlike their amorphous counterparts. However, device endurance has been found to be inadequate, probably due to the presence of some contaminants - notably interstitial oxygen - which has been found elsewhere to have adverse effects on the electrical characteristics of Si films. If well harnessed, we suggest Si structures grown by this novel growth technique could be well-suited for flash memory applications, particularly 3-D flash which requires process temperatures to be less than 400 °C.

The usage of organic materials in the manufacture of electronic polymer memory devices is on the rise. Polymer memory devices are fabricated by depositing a blend (an admixture of organic polymer, small molecules and nanoparticles) between two metal electrodes. The primary aim is to produce devices that exhibit two distinct electrical conductance states when a voltage is applied. These two states can be viewed as the realisation of non-volatile memory. This is an interesting development; however, there are a number of theories that have been proposed to explain the observed electrical behaviour. We have proposed a model that is based on electric dipole formation in the polymer matrix. Here, we investigate further the proposed model by deliberately creating electric dipoles in a polymer matrix using electron donors (8-Hydroxyquinoline, Tetrathiafulvalene and Bis(ethylenedithio)tetrathiafulvalene) and electron acceptors (7,7,8,8-Tetracyanoquinodimethane, Tetracyanoethylene and Fullerene) small molecules.Two types of structures were investigated (i) a metal/blend of polymer and small molecules/metal (MOM), device and (ii) a metal/insulator/blend of small molecules and polymer/semiconductor (MIS) architecture. A blend of polymer and small organic molecules was prepared in methanol and spin-coated onto a glass substrate marked with thin aluminium (Al) tracks; a top Al contact was then evaporated onto the blend after drying - this resulted in a metal-organic-metal structure. The MIS structures consisted of an ohmic bottom Al contact, p-type Si, a polymer blend (two small organic molecules and insulating polymer), followed by polyvinyl acetate and finally a top, circular Al electrode. In-depth FTIR studies were carried out to understand the observed electrical behaviour. An electrical analysis of these structures was performed using an HP4140B picoammeter and an HP 4192A impedance analyser at a frequency of 1 MHz.

Low temperature (≤400°C) growth of polycrystalline silicon (poly-Si) is carried out using plasma-enhanced chemical vapour deposition. After an initial preparation step poly-Si was grown on the substrates. Optical band gap studies of the poly-Si films have been correlated to hydrogen content of the films as well as to their photoconductivity. Furthermore, the suitability of these films for use as information storage materials for future generation 3-D flash memory devices is investigated using capacitance-voltage (C-V) measurements via metal-insulator-semiconductor device structures. C-V analysis indicates strong charge storage behavior for the poly-Si films.

The influence of native point defects on the electrical and optical stability of zinc oxide (ZnO) layers in air produced by reactive RF magnetron sputtering is investigated. ZnO thin films are strongly affected by oxygen (O2) molecules in ambient atmosphere. For instance, surface defects such as oxygen vacancies act as adsorption sites of O2 molecules, and the chemisorption of O2 molecules depletes the surface electronic states and reduces channel conductivity. Thin films of ZnO produced have electrical resistivities between 8.6 × 103 and 8.3 × 108 Ω-cm, and were found to be electrically-stable in air. TFTs fabricated using these films exhibited effective mobilities of ∼3 cm2V-1s-1 and the threshold voltage shifts by < 5 V under gate bias stress of 1 MV/cm for up to 104 s.

We describe the use of C60 fullerene molecules as the charge storage medium in an insulating poly-vinyl-phenol (PVP) polymer. The simple metal–organic–metal (MOM) sandwich structure devices deposited from solution exhibit distinct high and low conduction states, which can be used to program read, write and erase memory operations. The charge transfer and retention in C60 molecules at room temperature has been confirmed by capacitance–voltage and Raman spectroscopy measurements. Conducting atomic force microscopy has been used to demonstrate that high and low conductance states persist even at the nanoscale.

We demonstrate a memory device, using gold nanoparticles as charge storage elements deposited at room temperature by chemical processing. The nanoparticles are deposited over a thin thermal silicon dioxide layer that insulates them from the device silicon channel. An organic insulator deposited by the Langmuir-Blodget technique at room temperature separates the aluminium gate electrode from the nanoparticles. The device exhibits significant threshold voltage shifts after application of low voltage pulses (

Paul made the major contribution to this output, which formed the basis of one invited international talk (13th International Workshop on the Physics of Semiconductor, India), an invited article (in the Journal Small) and has secured international and national collaborations (Prof. D Tsoukalas) National Technical University, Athens, Greece and (Dr A Podhorodecki) Institute of Physics & Wroclaw University of Technology, Wroclaw, Poland and (Dr M Green) King’s Collage London.

Thin films of hydrogenated amorphous carbon ( a-C:H ) deposited by radio frequency plasma-enhanced chemical vapour deposition (rf-PECVD) have been studied for various applications. An interesting property of these films is their high breakdown strength ( 107 Vcm−1 ). This property of a-C:H can be exploited in high breakdown heterostructure diodes or as passivation layers and insulator layers in MIS devices. Reports on the applications of a-C:H/Si diodes exist in the literature. Diodes in which the a-C:H films have been deposited by rf-PECVD, have been reported only once. In this article the diodes produced reportedly failed to exhibit reproducible I-V characteristics under high voltage stress. We have investigated the process dependence of structural and electrical properties of rf-PECVD a-C:H films deposited at room temperature from a CH4/Ar gas mixture (at a pressure of 100 mTorr) using a capacitively coupled rf-PECVD. We observe a clear correlation between the dc-self bias and the rectification ratio of a-C:H/Si heterojunction diodes. Optimised diodes show rectification ratios upto 104 and a stable reverse breakdown voltage, typically around 850 V. I-V and C-V measurements show no evidence of hystersis. Scanning Electron Microscopy was carried out to determine the quality of the films deposited. Micro-Raman analysis was used to estimate the ID/IG ratio in the films deposited under different dc-self bias.

In this work, we demonstrate a MISFET memory device that incorporates a monolayer of Langmuir-Blodgett (LB) deposited gold nanoparticles as floating gate charge storage elements. The FET device is fabricated on a SOI substrate using conventional silicon processing. The nanoparticle layer is separated from the channel area of the FET with a 5 nm thermal SiO2 layer and is isolated from Al gate contact with a LB-deposited organic insulator layer. The memory effect is tested using voltage pulses on the gate of the device and monitored through drain current measurements. The nanocrystals can be charged either from the channel through the thermal oxide layer by applying pulses smaller than 5 V or from the gate through the organic insulator for higher voltage depending on the pulse duration.

In recent years, interest in applications of organic materials in electronic devices (light emitting diodes, field effect transistors, solar cells), has increased rapidly. The advantages of organic materials are the ease of processing, lower production costs and structural flexibility allowing achievement of the desired electrical and mechanical characteristics. Very recently, there have been demonstrations of blends of polymer and metal nanoparticles and/or small organic molecules in memory devices; such memory devices are called polymer memory devices (PMDs). These devices show two electrical conductance states (“high” and “low”) when voltage is applied, thus rendering the structures suitable for data retention. These two states can be viewed as the realisation of non-volatile electrical memory. There is always growing need to look for inexpensive, fast, high-density memory devices with longer retention times and PMDs do possess some of these aforesaid criteria. Albeit, there is a rapid development in this area, the memory mechanism is still unclear. This work attempts to analyse the memory effect in PMDs and proposes a theory based on experimental data. The thin film polymer blends (polyvinyl acetate, polyvinyl alcohol and polystyrene) and small organic molecules were deposited by spin coating onto a glass substrate marked with thin metal tracks. A top contact was evaporated onto the blend after drying this resulted in a metal-organic-metal (MOM) structure. MOM devices with different metal electrodes (a series of metals with different work functions Al, In,Cu,Cr, Ag and Au) were used to understand the exact electrical transport mechanism through the blend and the individual polymers. An in-depth electrical analysis of these MOM devices was carried out using an HP4140B picoammeter (current-voltage) and an LCR HP4192 bridge. FTIR and UV-VIS spectroscopy were also conducted in order to understand blend properties and the effect of the same, if any, on the electrical charging mechanism in the PMDs. INTRODUCTION Organic materials exhibit very interesting properties and in recent years the interest to use these materials in electronic device has shown a rapid increase. For example, numerous organic materials have been proposed and demonstrated for their possible applications in solar cells, thin film transistors and light emitting diodes for the last two decades [1,2,3]. Recently, the use of organic materials has been demonstrated in electrical memory device [4-7]. Memory effect has been reported in a large variety of organic materials and device configurations. The fundamental structure of organic memory devices consists of cross-point elements with two parallel top and * Contact author email: spaul@dmu.ac.uk Mater. Res. Soc. Symp. Proc. Vol. 1114 © 2009 Materials Research Society 1114-G12-09

Rode pointed out that periodically-disturbed surface morphology can occur on epilayers grown on slightly misoriented substrates. Johnson and Legg investigated Rode's prediction in Metalorganic Vapour Phase Epitaxy (MOVPE) of AIGaAs at fixed V/III ratio, but no report is available on the faceting as a function of V/III ratio in epilayers of GaAs grown by MOVPE. We have therefore investigated faceting, as function of V/III ratio, during the growth of GaAs by MOVPE at atmospheric pressure, and have found that faceting in epilayers, grown by MOVPE, is not only dependent on misorientation angle but also on the V/III ratio. These layers have characterized by optical microscopy, SEM, photoluminescence(PL), and Hall ineasuremwnts. Direct correlation between surface morphology and near-band-edge PL has been observed. Mirror-like smooth morphology was obtained at a relatively low V/Ill ratio (≈ 15); faceting occur as a ratio is gradually is increased to about 25 and beyond. On the basis of our study, we believe the dimensions of faceting on micrometer scale can be tailored by varying the V/III ratio. These patterns can be utilized in the fabrication of optoelectronic and transferred electron devices, large scale integration of the later being possible.