Surface potential measurement of As-doped homojunction ZnO nanorods by Kelvin probe force microscopy

In this study, we demonstrate the electronic properties of As-doped homojunction ZnO nanorods by Kelvin probe force microscopy (KPFM). The self-assembled undoped/As-doped homojunction ZnO nanorods were grown on Si (111) substrates by using vapor phase transport. Individual nanorods were transferred onto Au films grown on Si substrates. The morphology and surface potentials of the ZnO nanorods were simultaneously measured by KPFM. For the homojunction nanorods with ~200 nm in diameter, the KPFM images show obviously doping transition across the junction region, indicating local doping types. Also, the surface potential difference across the junction was measured to be ~85 mV, which could be the result from the work function difference between undoped and As-doped region. It is in good agreement with the work function difference of ~95 meV between the As-doped p-type and intrinsic n-type nanorods in the same measurement condition. The work function of the doped ZnO nanorods measured by KPFM is discussed in terms of surface band bending induced by surface states of ZnO. Copyright © 2011 John Wiley & Sons, Ltd.