Effect of O2 plasma pretreatment on structural and optical properties of ZnO films on PES substrate by atomic layer deposition

ZnO films were deposited on the O2 plasma treated polyethersulfone (PES) substrates by atomic layer deposition. X-ray diffraction (XRD) measurements reveals that the grains in ZnO films show strongly (0 0 2) preferential orientation, when the duration of plasma pretreatment increases. The decreased grain size and improved crystallinity results in the decreased surface roughness of ZnO films. In contrast, when the duration of plasma pretreatment increases to 60 min, the surface roughness increases again due to the increased grain size and worse crystallinity. In photoluminescence measurement, slight blue shift of near-band-edge emission occurs with increasing duration of plasma pretreatment up to 30 min.