Comparative study of the electrical characteristics of ALD-ZnO thin films using H2O and H2O2 as the oxidants

Abstract

ZnO thin films were deposited via atomic layer deposition (ALD) using H2O and H2O2 as oxidants with substrate temperatures from 100 degrees C to 200 degrees C. The ZnO films deposited using H2O2 (H2O2-ZnO) showed lower growth rates than those deposited with H2O (H2O-ZnO) at these temperature range due to the lower vapor pressure of H2O2, which produces fewer OH- functional groups; the H2O2-ZnO films exhibited higher electrical resistivities than the H2O-ZnO films. The selection of H2O2 or H2O as oxidants was revealed to be very important for controlling the electrical properties of ALD-ZnO thin films, as it affected the film crystallinity and number of defects. Compared to H2O-ZnO, H2O2-ZnO exhibited poor crystallinity within a growth temperature range of 100-200 degrees C, while H2O2-ZnO showed a strong (002) peak intensity. Photoluminescence showed that H2O2-ZnO had more interstitial oxygen and fewer oxygen vacancies than H2O-ZnO. Finally, both kinds of ZnO thin films were prepared as transparent resistive oxide layers for CIGS solar cells and were evaluated.