ZnO:Al Thin Films with Buffer Layers Fabricated via Nitrogen Mediated Crystallization: Effects of N₂/Ar Gas Flow Rate Ratio

Abstract

Effects of N₂/Ar gas flow rate ratio on the crystallinity of sputtered ZnO films fabricated via nitrogen mediated crystallization (NMC) have been clarified. Introduction of small amount of N₂ (N₂/Ar = 4/20.5 sccm) drastically improves the crystal orientation and enlarges grain size of the NMC-ZnO films, where FWHM of XRD patterns for 2θ-ω and ω scan of (002) plane are 0.17° and 2.6°, respectively. A further increase in N₂/Ar flow rate ratio deteriorates the crystallinity, since excess N atoms in the films disarrange the crystal structure of ZnO. Furthermore, ZnO:Al (AZO) films with high crystallinity have been successfully fabricated by utilizing the NMC-ZnO films deposited at N₂/Ar = 4/20.5 sccm as buffer layers. 100-nm-thick AZO films with a resistivity of 6.8×10^-4 Ωcm and an optical transmittance higher than 80% in a wide wavelength range of 500 nm to 1500 nm has been obtained.