Atomic Layer Deposition of Gallium-Doped Zinc Oxide Transparent Conducting Oxide films
- PDF / 210,487 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 79 Downloads / 283 Views
Atomic Layer Deposition of Gallium-Doped Zinc Oxide Transparent Conducting Oxide films Paul R. Chalker,1 Paul A. Marshall,1 Simon Romani,1 Matthew J. Rosseinsky,2 Simon Rushworth, 3 Paul A. Williams,3 John Buckett, 4 Neil McSporran 4 and John Ridealgh 4. 1
Materials Science and Engineering, University of Liverpool, Liverpool, UK L69 3BX Department of Chemistry, University of Liverpool, Liverpool, UK L69 7ZD 3 SAFC Hitech, Power Road, Bromborough, Wirral, Merseyside, UK CH62 3QF 4 Pilkington Technology Management Limited, Hall Lane, Lathom, Ormskirk, Lancashire, UK, L40 5UF 2
ABSTRACT Thin transparent conducting oxide (TCO) films of gallium-doped zinc oxide have been deposited on glass substrates by atomic layer deposition (ALD) using diethyl zinc, triethyl gallium and water vapour as precursors. The gallium-doped zinc oxide films were deposited over the temperature range 100-350°C. Transmission electron microscopy reveals that the asdeposited films are polycrystalline in character. The electrical resistivity of the gallium-doped zinc oxide films was evaluated using four-point probe and contactless measurement methods as a function of film thickness. The lowest sheet resistance of 16 / ڙwas measured from a film thickness of 400nm and a gallium content of 5 atomic percent. The electron Hall mobility of this film was 12.3 cm2/Vs. The visible transmittance of the films was 78% with a haze of 0.2%. INTRODUCTION Transparent conducting oxide (TCO) thin films are being increasingly exploited in a range of technological applications including architectural glazing, photovoltaic solar cells, flat panel displays, light emitting diodes and lasers. For optoelectronic devices, the combination of high electrical conductivity (104 Ω-1 cm-1) and optical transparency (>80%) across the visible spectral range are enabling in terms of reduced electrical power consumption and high optical power output. Tin-doped indium oxide (In2-xSnxO3, ITO) fulfils all of these requirements and has become a ‘benchmark’ when qualifying the performances of other TCO’s such as fluorine-doped tin oxide or doped zinc oxide [1]. Nevertheless, extensive research activity continues to be focused on the development of less expensive and non-toxic alternatives. Doped zinc oxide based TCO’s are of particular interest and various substituents including group-III (B, Al, Ga, In) elements for Zn; or group-VII (F, Cl, I) elements for O have been investigated. Other impurity doping systems have been characterised including N, Si, Ge, Y, Sc, V, Ti, Zr, Hf, amongst others. The overwhelming majority of these studies have been made using physical vapour deposition techniques such as sputtering, pulsed laser deposition, molecular beam epitaxy or ion plating. Chemical vapour deposition (CVD) processes have been demonstrated for TCO’s via metalorganic CVD and more recently atomic layer deposition (ALD). The latter has been adopted by industry for the deposition of metal oxides [2], because it has a number of advantages over other deposition techniques. These include the
Data Loading...
