Deposition of high-electron-mobility transparent conducting zinc oxide thin films by DC magnetron sputtering in gas mixture of argon and hydrogen

Abstract

Transparent conducting zinc oxide thin films having high electron-mobility are deposited on glass substrates by DC magnetron sputtering in gas mixture of argon and hydrogen at room temperature. Introducing a little amount of hydrogen gas into sputtering Ar gas can remarkedly improve the electron mobility in ZnO thin films. With gas flow rate ratios of hydrogen to argon range from 7.2 % to 19.2 %, ZnO films with hydrogen (ZnO:H) have stable and low resistivity of 6.6×10^-4 Ω.cm. At H₂/Ar flow rate ratio 7.2 %, electron Hall mobility in ZnO:H film reaches a maximum value of 61 cm².V^-1.s^-1. This value is much higher than the one of 23 cm².V^-1.s^-1 in pure ZnO films under the same deposition condition. Morever, electron density of 1.5´10²⁰ cm^-3 in ZnO:H films is also higher than the one of 6×10¹⁹ cm^-3 in pure ZnO films. XRD and FESEM show that the average crystalline-grain size in ZnO:H films are larger than the one in pure ZnO films. The 600-nm-thick ZnO:H films (substrate included) have average transmission of 83 % in the wide wavelength range of 380-1100 nm and low sheet resistance of 11 W/square.