Effects of Nitrogen on Crystal Growth of Sputter-Deposited ZnO Films for Transparent Conducting Oxide

We have studied the effects of the N-2 gas flow rate on the surface morphology of ZnO films deposited by the sputtering of a ZnO target using Ar/N-2. Height-height correlation function (HHCF) analysis indicates that introducing a small amount of N-2 (<5 sccm) to the sputtering atmosphere enhances adatom migration, leading to a larger grain size in the ZnO films associated with an increase in the lateral correlation length. The HHCF analysis also reveals that films deposited with and without N-2 exhibit a self-affine fractal surface structure. We demonstrate that utilizing such ZnO films deposited using Ar/N-2 as buffer layers, the crystallinity of ZnO:Al (AZO) films on the buffer layers can be greatly improved. The electrical resistivity of 100-nm-thick AZO films decreases from 1.8 x 10(-3) to 4.0 x 10(-4) Omega.cm by utilizing a ZnO buffer layers prepared at N-2 flow rate of 5 sccm. (C) 2013 The Japan Society of Applied Physics