We have studied the effects of the N2 gas flow rate on the surface morphology of ZnO films deposited by the sputtering of a ZnO target using Ar/ N2. Height-height correlation function (HHCF) analysis indicates that introducing a small amount of N2 (<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/N2 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 × 10-3 to 4:0 × 10-4 Ω·cm by utilizing a ZnO buffer layers prepared at N2 flow rate of 5 sccm.
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