Electrical properties of ZnO thin films grown on a-plane sapphire substrates using catalytically generated high-energy H2O

Abstract

The electrical properties of zinc oxide (ZnO) epitaxial films grown by chemical vapor deposition (CVD) using high-energy H2O generated by H2–O2 reactions on Pt nanoparticles were evaluated. High-energy ZnO precursors formed by the reaction between dimethylzinc gas molecules and H2O molecules were supplied to the substrate surface. The ZnO epitaxial films were grown directly on a-plane sapphire (a-Al2O3) substrates at 773K without any buffer layer. The electron mobility (μH) at room temperature increased from 30 to 190 cm2V−1s−1 with increasing film thickness from 100nm to 2800nm. The μH increased significantly with decreasing temperature to approximately 100–150K, but it decreased at temperatures less than 100K for films thicker than 500nm. The μH of the ZnO film (189 cm2V−1s−1) at 290K increased to 660 cm2V−1s−1 at 100K. In contrast, μH hardly changed with temperature for films thinner than 500nm. According to a two-layer Hall-effect model, the μH and electron concentration of the upper layer were corrected based on the above results, assuming that the degenerate layer had a thickness of 100nm.