Preparation of epitaxial films of the transparent conductive oxide Al:ZnO by reactive high-pressure sputtering in Ar/O2 mixtures

Abstract

Transparent conductive metal oxides are interesting materials for various optoelectronic applications including solar cells and flat panel displays. This study focuses on the in situ deposition of aluminum-doped zinc oxide (AZO) thin layers on c-axis oriented sapphire substrates by dc sputtering and on the structural and electrical characterization. The films have a typical thickness of 90nm and a roughness of 10nm root mean square. An Al/Zn ratio of 2.4at% Al was determined by X-ray photoelectron spectroscopy. X-ray diffraction shows a preferential growth in the (0002) c-axis direction. Films have an average transparency of 90% in the visible-light spectrum, a room-temperature resistivity of 3.7x103cm and a carrier mobility of 6.7 cm(2) V-1 s(-1).