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ZnO; Thin Film; Optical Properties; Defect Levels; Scanning Probe Mircroscopy; STM-Luminescence
Abstract:
Luminescence spectroscopy with an STM is used to analyze the role of lattice defects in crystalline ZnO films grown on Au(111). The films exhibit a strong band-recombination peak at 373 nm as well as three maxima at higher wavelength, indicating the presence of oxide defects. To identify their nature, we systematically alter the preparation conditions by treating the films with UV radiation, hydrogen, and oxygen and at elevated temperature. From concomitant changes in the emission response, we are able to assign the subgap peaks to specific O and Zn defects in the wurtzite lattice. Our conclusions are discussed in light of recent DFT calculations.