AVS 53rd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuM

Paper EM-TuM6
Transparent Conducting Zinc Oxide Thin Films Doped with Aluminum, Molybdenum, and Vanadium

Tuesday, November 14, 2006, 9:40 am, Room 2003

Session: Zinc Oxide
Presenter: J.N. Duenow, Colorado School of Mines
Authors: J.N. Duenow, Colorado School of Mines
T.A. Gessert, National Renewable Energy Laboratory
T.M. Barnes, National Renewable Energy Laboratory
T.J. Coutts, National Renewable Energy Laboratory
Correspondent: Click to Email
Transparent conducting oxide (TCO) thin films are an integral part of photovoltaic cells, flat-panel displays, and electrochromic windows. The most commonly used TCO, tin-doped indium oxide (ITO), offers excellent performance, but in recent years material costs have risen dramatically because of increased demand for limited indium resources. We are investigating alternative TCOs based on zinc oxide (ZnO). As is the case with many TCO materials, investigations by many groups have not provided clear guidance toward significant improvement of ZnO material quality. We have examined whether electron transport can be enhanced by incorporating dopants with multiple valence states into the ZnO matrix--specifically, whether molybdenum (Mo; valence +6, 5, 4, 3, 2) or vanadium (V; +5, 4, 3, 2) can surpass the performance of aluminum (Al; +3). We deposited these ZnO-based materials by radio frequency magnetron sputtering from fully oxidized targets. We evaluated electrical, optical, and structural properties of these films using Hall measurements, spectrophotometry, and X-ray diffraction, respectively. Baseline studies of undoped ZnO revealed surprisingly high mobility values of 48 cm@super 2@/Vs in films deposited with a hydrogen-to-argon partial pressure ratio of 0.3% at a substrate temperature of 200°C; corresponding carrier concentrations were ~3 x 10@super 19@ cm@super -3@. Similar baseline studies with Al-doped ZnO resulted in films with typical mobility values of 25 cm@super 2@/Vs and carrier concentrations of ~6 x 10@super 20@ cm@super -3@ when deposited in 100% argon at 200°C. Initial results for Mo-doped films deposited in a hydrogen partial pressure ambient show that Mo is an effective dopant of ZnO, suggesting that multi-valent dopants may have value in TCO materials beyond that considered previously. We also present studies of V doping. This abstract is subject to government rights.