The effects of thermal annealing on ZnO thin films grown by pulsed laser deposition

ZnO thin films were grown on silicon (100) by pulsed laser deposition. High ly textured crystalline ZnO thin films can be grown at 600 degrees C. The f ilms were then annealed at 600 degrees C in oxygen. The effects of annealin g on chemical composition of the ZnO films were investigated by x-ray photo electron spectroscopy (XPS) and Raman spectroscopy. The XPS spectra indicat e that water has been adsorbed and then dissociated into H and OH groups. T he surface properties of ZnO were studied both by scanning tunneling micros copy and scanning tunneling spectroscopy (STS). A narrow potential well has been formed on the surface of the ZnO thin films due to high density of su rface states and negatively biasing the ZnO thin films during STS measureme nt. The discrete energy levels can be measured by STS. (C) 2000 American In stitute of Physics. [S0021-8979(00)03113-3].