Initial preferred growth in zinc oxide thin films on Si and amorphous substrates by a pulsed laser deposition

Abstract

Zinc oxide (ZnO) thin films have been prepared on Si (0 0 1), Si (1 1 1), glass, and thermally grown SiO 2/Si (0 0 1) substrates using a pulsed laser deposition. High-resolution transmission electron microscopy and selected-area electron diffraction showed that there are neither amorphous layer nor random oriented polycrystalline ZnO layer at the film/substrates interfaces even if the films were formed at a relatively low substrate temperature of 400°C. Typically, consecutive c-axis oriented ZnO film on Si (0 0 1) substrate with deviation angle below ±4.5° in the 30 nm thick ZnO film is formed directly on the about 2.5 nm-thick amorphous native silicon oxide layer. These results indicate that during the initial film growth particles may satisfy the tetrahedral coordination, which results in nucleation with c-axis orientation even on the amorphous substrate. The phase evolution and preferred orientation of the ZnO films at the initial stage of the film growth at the interface are discussed.