The electrical properties of zinc oxide (ZnO) epitaxial films grown by chemical vapor deposition (CVD) using high-energy H2O generated by H-2-O-2 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 773 K without any buffer layer. The electron mobility (mu(H)) at room temperature increased from 30 to 190 cm(2)V(-1) s(-1) with increasing film thickness from 100 nm to 2800 nm. The mu(H) increased significantly with decreasing temperature to approximately 100-150 K, but it decreased at temperatures less than 100 K for films thicker than 500 nm. The mu(H) of the ZnO film (189 cm(2)V(-1) s(-1)) at 290 K increased to 660 cm(2)V(-1) s(-1) at 100 K. In contrast, mu(H) hardly changed with temperature for films thinner than 500 nm. According to a two-layer Hall-effect model, the mu(H) and electron concentration of the upper layer were corrected based on the above results, assuming that the degenerate layer had a thickness of 100 nm. (C) 2013 Elsevier B. V. All rights reserved.