Improvement in crystalline quality and surface smoothness of ZnO film by multi-step deposition process

The effect of multi-step deposition process on the crystalline quality and surface smoothness of ZnO film was investigated. ZnO films were composed of multi-layers, in which each layer was deposited at different temperatures. The maximum intensity and the smallest FWHM of (0 0 2) diffraction peak in XRD spectrum were observed for the multi-layered ZnO film of which each layer was deposited at progressively higher temperatures. In addition, the smoothest film surface was also observed for the ZnO film deposited through multi-step process in which deposition temperatures gradually increase. On the other hand, the large difference between the deposition temperatures in multi-step process did not result in the significant improvement of the crystalline quality of ZnO film. The ZnO film prepared by using multi-step process had high transmittance over 70% in visible region and the optical band gap of 3.22 eV.