ZnO（002） films with different thicknesses, grown on Al2O3 （006） substrates by metal-organic chemical vapor deposition（ MOCVD）, were etched by Ar ion beams. The samples were examined by D8 X-ray diffraction, scanning electron microscopy（SEM）, and photoluminescence（PL） spectrometry. The structural properties vary with the increasing thickness of the films. When the film thickness is thin, the phi（Φ） scanning curves for ZnO（103） and sapphire（116） substrate show the existence of two kinds of orientation relationships between ZnO films and sapphire, which are ZnO（002）//Al2O3 （006）, ZnO（ 100）//Al2O3 （110） and ZnO（002）//Al2O3 （006）, ZnO（ 110）//Al2O3 （110）. When the thickness increases to 500 nm there is only one orientation relationship, which is ZnO（002）// Al2O3 （006）, ZnO [ 100]//Al2O3 [ 110]. Their photoluminescence（PL） spectra at room temperature show that the optical properties of ZnO films have been greatly improved when increasing the thickness of films is increased.
ZnO（002） films with different thicknesses ranging from 7 to 300 nm were grown on sapphire（006） substrates via metal-organic chemical vapor deposition （MOCVD）. The two-dimensional（2D） planar layer and the three-dimensional（3D） island layer were studied by using of X-ray diffraction（XRD） rocking curves and atomic force microscopy （AFM）. The room temperature photoluminescence （PL） spectra show a blue shift of the peak positions of the uhraviolet（UV） emission with increasing film thickness. The blue shift is remarkably high（393-380 nm） when an increase in film thickness（7-15 nm） is accompanied by the change of structure from a 2D planar layer to a 3D island layer. The PL spectra at 77 K also indicate that there are different transition mechanisms in the film thickness from a 2D planar layer to a 3D island layer near the 2D layer region.
The orientation of the nano-columnar ZnO films grown on sapphire using the technique of metal-organic chemical vapor deposition （MOCVD） exhibits deviation because of the mismatch between the crystal lattices of the films and the sapphire substrate. A high-throughout X-ray diffraction method was employed to determine the crystal orientation of the ZnO films at a time scale of the order of minutes based on the general area detection diffraction system （GADDS）. This rapid, effective, and ready method, adapted for characterizing the orientation of the nano-columnar crystals is used to directly explain the results of observation of the X-ray diffraction images, by the measurements of the orientations of the crystal columns of the ZnO films along c-axis and in parallel to ab plane.
