Structural Order of Nanocrystalline ZnO Films

Abstract

Long- and short-range structural order of nanocrystalline ZnO films grown using single source chemical vapor deposition (SS-CVD) of basic zinc acetate Zn 4 O(CH 3 COO) 6 have been investigated. The addition of a low background pressure of H 2 O during SS-CVD provides a mechanism for varying the structural properties through control of impurities occluded within the film. The structure of the resultant films can be varied from amorphous (10 at. % impurities) to highly crystalline with preferred c -axis orientation (less than 1 at. % impurities). Transmission electron microscopy, X-ray diffraction, and electron spectroscopy measurements have been used to investigate the structure of the film grains and to explain the observed correlation between impurity concentration and size of the film crystallites (3−40 nm). The results of extended X-ray absorption fine structure studies indicate that the orientation of the crystallites (random or c -axis) is dependent on the atomic short-range structural properties. Self-texturing, an intrinsic property of ZnO, is inhibited for high defect densities.