Growth of ZnO films on R-plane sapphire substrates by atmospheric-pressure chemical vapor deposition using Zn powder and H2O as source materials

Abstract

Films of ZnO have been grown on R-plane sapphire substrates by atmospheric-pressure chemical vapor deposition (AP-CVD) using Zn powder and H2O as source materials. Variation in growth rate as a function of substrate temperature can be divided into three regions: re-evaporation region, mass transport controlled region, and surface controlled region. Scanning electron microscope observations revealed that the surface morphology of the film is dependent not only on substrate temperature but also on Zn source and H2O source temperatures. X-ray diffraction patterns of most of the films showed a dominant (110) peak, indicating highly A-axis oriented growth. A single crystalline A-plane ZnO film without mixed domain was successfully grown by optimizing the growth condition. Visible region photoluminescence changed from orange-red emission to blue-green emission systematically by adjusting Zn source and H2O source temperatures. This result suggests the possibility of defect control in our AP-CVD system. For the films grown at TS=700°C in the mass transport controlled region, resistivity decreased from 0.45to0.007Ωcm as TH2O rised from 54to75°C.