THE GROWTH AND ANNEALING OF SINGLE CRYSTALLINE ZNO FILMS BY LOW-PRESSURE MOCVD

Abstract High-quality c -axis-oriented single-crystal ZnO films have been successfully grown on the (0 0 0 2) sapphire substrate by the low-pressure metal organic chemical vapor deposition technique. The effect of doping and annealing on the optical and structural properties has been investigated by means of X-ray diffraction (XRD), photoluminescence (PL) spectrum and atomic force microscopy (AFM). Annealing at high temperature was found to enhance the intensity of the (0 0 0 2) XRD peak and decrease the c -axis oriented lattice constant. However, the (0 0 0 2) XRD peak for the N-doped sample shifted to a low degree due to tensile stress possibly caused by nitrogen doping. The green–yellow band emission was observed in the room temperature PL spectrum of the undoped sample while the blue band emission emerged in the PL spectrum of the N-doped one. Low-temperature PL spectrum of the ZnO films was dominated by a sharp bound exciton line. Possible causes to the above differences will be given and discussed.

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