David Henry

Transparent electronics are an essential ingredient in many new technologies which are emerging in the 21st century - high efficiency solar cells[ll, interactive and transparent displays, energy efficient windows, and photonics for communications and computing[2J. The development of functionalised transparent conductive oxide materials (TCOs), in terms of abundant, cheap and environmentally friendly, is critical for materials science in such applications. Specifically, an impmiant research goal is to find substitutes for the dominant TCO material indium tin oxide (ITO), made from indium which is scarce, expensive and toxic. Zinc oxides doped with small amounts of aluminium (AZO), are promising candidates for such a substitute but generally don't perform as well as IT0[2l. Gallium co-doping with aluminium improves AZO performance significantly, but raises similar concerns to ITO, in terms of the scarcity and high cost of gallium. This project aims to enhance the conductivity of AZO thin films-by adding a thin 'seed' layer co-doped with AI and minimum Ga concentration (AGZO). The project employed solution based sol-gel technique for synthesising AZO/GZO nanoparticles and then deposited on glass substrates through a spin coating process, followed by thermal annealing treatment. The optical properties, crystal structure and surface morphology of the films were characterised using UV-vis spectroscopy, X-ray diffraction and scanning electron microscopy. Composite multilayer films, with thickness around 400nm, exhibit transmittance above 90% across the visible range and resistivity approximately 10 O•cm. Preliminary results indicate significant improvement in AZO films with the co-doped AGZO layer, compared with AZO films alone. Compared to uniformly doped AGZO films, the composite multilayer films exhibited similar performance, but with only 20% of the gallium consumed.

Among various transparent conductive materials, indium tin oxide (ITO) demonstrates a major dominant role due to its high optical transparency and high electrical conductivity. Doping ITO with a transition metal, such as Ti, Mo, Zr, Cu, can improve the optoelectronic properties of such coatings. In this study, titanium- doped ITO (Ti:ITO) thin film coatings were developed via a low cost and simple sol-gel spin coating technique. The effect of Ti concentration and annealing temperature on the structural, morphological, optical and electrical properties of the synthesized films (350nm thickness) were characterised by FESME, XRD and UV-Vis techniques. XRD analysis confirmed the cubic bixbyite structure of polycrystalline indium oxide phase. The crystallinity, optical transparency and electric conductivity of the thin film coatings were improved with increase of annealing temperature. At 500°C annealing temperature the grain sizes, verified by FESEM, of the thin films were 79 and 65 nm for doping concentration of 4 at% and 2 at% Ti, respectively. Furthermore, at this temperature, optimum electrical resistivity (1.6x 10-4 n.cm) and optical transmittance (92%) were achieved. These results compare favourably with the resistivity (2.9x 1 o-4 n.cm) and transparency around (90%) founded by Liu et.al and Paeng et. al respectively [1, 2].

There has been considerable interest in recent years in the effects of doping of light metal materials with transition metals to improve the thermodynamics and kinetics of hydrogen chemisorption and desorption. Foremost among these is the work of Bogdanovic and Schwickardi (1997) who demonstrated that doping alkali metal hydrides with a few mol% of Ti can lead to reversible decomposition at reasonable temperatures and pressures. Theoretical studies (Chaudhuri 2005, 2006) of Ti-doped NaAlH 4 indicate that the Ti dopant is responsible for catalysing H 2 chemisorption when the Ti atoms are in specific local arrangements. The reactivity, electrostatic fields and surface features of small metal clusters can differ significantly from that of bulk materials and is often dependant on not only the composition but the size of the cluster. While theoretical and experimental studies have shown that the interaction of hydrogen atom with aluminium clusters is thermodynamically favoured, experimental studies have suggested that the kinetics for chemisorption of hydrogen molecule on pure aluminium clusters are quite slow. Experimental studies of the interaction of molecular hydrogen with aluminium clusters have generally been carried out in the gas phase with charged clusters to enable isolation and detection of the products (Cox, 1988) (Jarrold, 1988). In this study we investigate the interaction of diatomic hydrogen with a series of neutral and charged X-centred aluminium clusters (Al 12X, X = Mg, Al, Si). We use the PBE/6-311G(d, p) and PBE/DNP levels, which have been found to give close agreement with CCSD/6-31G(d, p) for the ground state structures of Al 12X clusters and ions (Henry, 2008).