Formation of a ZnO2 layer on the surface of single crystal ZnO substrates with oxygen atoms by hydrogen peroxide treatment

Formation of a ZnO2 layer by H2O2 treatment for single crystal ZnO (0001) substrates was studied. X-ray diffraction (XRD) peaks of ZnO2 with a pyrite structure were observed in XRD 2θ-ω scan patterns of the O-face of single crystal ZnO (0001) substrates with H2O2 treatment, but these peaks were not observed in patterns of the Zn-face of ZnO (0001) substrates with H2O2 treatment. XRD ω scan patterns of the ZnO (0002) plane of the O-face of single crystal ZnO (0001) substrates were broadened at the tail of the pattern by H2O2 treatment, but such broadening was not observed in that plane of the Zn-face. Grain structure of ZnO2 layers was clearly observed in atomic force microscopy (AFM) images for the O-face of ZnO (0001) substrates with H2O2 treatment. Spectra of X-ray photoelectron spectroscopy (XPS) of the O-face of ZnO (0001) substrates with H2O2 treatment showed a definite peak shift of the O 1s peak. It is thought that a pyrite structure of ZnO2 is easily formed around an O atom of the O-face of ZnO (0001) substrates. Results of XRD measurements, the AFM image, and XPS measurement of the H2O2-treated single crystal ZnO (1010) substrate that has oxygen atoms on the surface appeared to be the same as those of the O-face of ZnO (0001) substrates.