Crystallinity control of sputtered ZnO films by utilizing buffer layers fabricated via nitrogen mediated crystallization: Effects of nitrogen flow rate

Abstract

High quality ZnO:Al (AZO) films have been obtained by utilizing buffer layers fabricated via nitrogen mediated crystallization (NMC), where sputtering method is employed for preparation of both buffer layers and AZO films. Introduction of small amount of N2 (N2/(Ar+N2) = 16%) to the sputtering atmosphere of NMC-ZnO buffer layers drastically improves the crystallinity of buffer layers and thus AZO films. The most remarkable effect of the buffer layers is a significant reduction in the resistivity at high base pressure of background gases. The resistivity of conventional AZO films increases from 2.0 m O•cm to 70.0 O•cm with increasing the base pressure from 3×10-5 Pa to 1×10-3 Pa, while the resistivity of AZO films with NMC buffer layers increases from 0.5 mO•cm to 2.0 mO•cm, where the thickness of AZO film is 88 nm. Furthermore, AZO films with a sheet resistance of 10O/? and an optical transmittance higher than 80% in a wide wavelength range of 400–1100 nm have been obtained.