Structural order of nanocrystalline ZnO films

Long- and short-range structural order of nanocrystalline ZnO films grown u sing single source chemical vapor deposition (SS-CVD) of basic zinc acetate Zn4O(CH3COO)(6) have been investigated. The addition of a low background p ressure of H2O during SS-CVD provides a mechanism for varying the structura l properties through control of impurities occluded within the film. The st ructure of the resultant films can be varied from amorphous (10 at. % impur ities) to highly crystalline with preferred c-axis orientation (less than 1 at. % impurities). Transmission electron microscopy, X-ray diffraction, an d electron spectroscopy measurements have been used to investigate the stru cture of the film grains and to explain the observed correlation between im purity concentration and size of the film crystallites (3-40 nm). The resul ts of extended X-ray absorption fine structure studies indicate that the or ientation of the crystallites (random or c-axis) is dependent on the atomic short-range structural properties. Self-texturing, an intrinsic property o f ZnO, is inhibited for high defect densities.