Preparation and growth mechanism of nonpolar, semipolar and polar ZnO films: Correlation of preferred orientation, defects and optical properties

Abstract

In the study, ZnO films with different preferred orientations were controllably prepared by using NH3·H2O to modulate the pH0 of chemical bath deposition. The samples were all characterised by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), ultraviolet-visible spectrophotometry (UV–VIS), X-ray photoemission spectroscopy (XPS) and photoluminescence (PL). The results show that ZnO films with polar, semipolar and nonpolar preferred orientations can be synthesised in a controlled manner by varying the pH0. Meanwhile, the influence of NH3·H2O concentration on the growth process of ZnO films is investigated in detail, and the relationship between the preferred orientation and optical properties is preliminarily discussed. At pH0= 7.32, the films exhibited semipolar (101) preferred orientation, the highest optical transmittance (89.15 %), and the highest concentration of Zni in the films. This study provides a method for the controlled synthesis of ZnO films with polar, semipolar and nonpolar preferred orientations and offers new possibilities for ZnO-based transparent semiconductor devices.