Influence of film thickness and annealing temperature on the structural and optical properties of ZnO thin films on Si (1 0 0) substrates grown by atomic layer deposition

Abstract

In this paper, ZnO thin films with different thicknesses grown on Si (100) substrates by atomic layer deposition (ALD) method were annealed in nitrogen at the temperatures ranging from 200 to 900°C. The influences of film thickness and annealing temperature on the structural and optical properties of the ZnO films were systematically investigated by XRD, SEM and RT-PL. All the ALD-ZnO thin films show polycrystalline hexagonal wurtzite structure and a high preferential c-axis orientation. The results show that the crystallinity quality and luminescence performance are both improved by increasing the film thickness. In addition, the loss of oxygen which results in the formation of oxygen vacancies (VO) is the main reason for the green emission dominating visible band of annealed ZnO thin films. The visible band is dominated by different kinds of defects including oxygen vacancies (VO and VO+), and interstitial oxygen (IO) with increasing annealing temperature. High-quality ZnO thin films with good luminescence performance can be obtained for the films annealed at 800°C in nitrogen.