Paper SS+AS+EN-MoM5
Characterizations of Non-polar Polar Interfaces: Cr₂O₃ on ZnO (0001) and (000-1)

Monday, October 19, 2015, 9:40 am, Room 113

The growth of non-polar Cr₂O₃ on oppositely poled ZnO surfaces was characterized to determine how the polar substrate influences the properties of the non-polar film. Photoelectron spectroscopy (XPS and UPS), electron diffraction (RHEED and LEED), High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray reflectivity (XRR) have been performed to determine the growth mode, film quality and interfacial electronic properties are influenced by the substrate polarization. The growth is 2D; however, the films appear initially disordered on both substrates. With increasing film thickness, the films ordered with a well-defined epitaxial relationship. The HRTEM and XRD/XRR results for thicker films confirm a clear interface and well-defined lattice structure near the interface and throughout the film, indicating that above a critical thickness the entire film reorganizes into an ordered structure. The polar interfaces show a small but noticeable band offset that decayed with increasing film thickness. Statistical analysis of UPS valence band spectra revealed an enhanced density of states near the Fermi level for Cr₂O₃ on the positive surface consistent with stabilization of the positive interface by charge transfer; in contrast, no significant valence band differences were observed between bulk Cr₂O₃ and thin Cr₂O₃ thin layers on the negative surface. The results will be compared with those obtained for ZnO/Cr₂O₃/ ZnO (0001) and (000-1) to determine if the interfacial properties are sensitive to how the interface is formed.