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

Zinc oxide (ZnO) thin films have been prepared on Si (001),Si (111), glass, and thermally grown SiO2/Si (001) substrates using a pulsed laser depositi on. High-resolution transmission electron microscopy and selected-area elec tron diffraction showed that there are neither amorphous layer nor random o riented polycrystalline ZnO layer at the film/ substrates interfaces even i f the films were formed at a relatively low substrate temperature of 400 de greesC. Typically, consecutive c-axis oriented ZnO film on Si (001) substra te with deviation angle below +/-4.5 degrees in the 30 nm thick ZnO film is formed directly on the about 2.5nm-thick amorphous native silicon oxide la yer. These results indicate that during the initial film growth particles m ay 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 Nm growt h at the interface are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.