Time-Resolved Photoluminescence Properties of ZnO Thin Films Evaporated by Atomic Layer Deposition

We have studied time-resolved photoluminescence (PL) properties of ZnO thin films which were grown by layer-by-layer manner using atomic layer deposition (ALD) method. The deposited film thickness was estimated by X-ray reflectance spectroscopy, which proved that the ALD system deposited -1.57 Å/cycle in thickness. As-grown films showed typical band-edge and surface defect induced emissions. The evaluated PL lifetimes showed interesting trend as the film thickness approaching to exciton Bohr diameter. Moreover, PL lifetime imaging technique clearly showed the characteristic lifetime modulation with changing film thickness in both band-edge and surface defect emissions.