Fabrication of high-electron-mobility ZnO epilayers by chemical vapor deposition using catalytically produced excited water

Hot H2O jet evolved by the exothermic reaction of H2 with O2 on a Pt-dispersed ZrO2 catalyst was employed for gas-phase hydrolysis of dimethyl zinc to fabricate thin ZnO films. The X-ray diffraction pattern and photoluminescence spectra showed that the ZnO epilayers directly grown on a-sapphire substrate at 873 K had a defect free crystal structure close to a single crystal. The as-grown ZnO epilayers exhibited average transparency higher than 90% in the visible and infrared regions (400-2000 nm). The epilayers had high electron mobilities of 140-170 cm2 V−1 s−1 and low residual electron concentrations of 1.7-6×1017 cm−3 that are significantly better than those for ZnO films so far reported by conventional chemical vapor deposition and any other energy-consuming physical method such as pulse laser deposition and molecular beam epitaxy. The present method uses the chemical energy from only H2 and O2, which is energy-saving and ecologically friendly, while it is superior in high-quality ZnO fabrication. It is also pointed out that the method raises unlimited possibilities for a wide range of the fabrication of high-quality metal oxide epilayers, because of the availability for various volatile alkyl metals.