Probing Surface Band Bending of Surface-Engineered Metal Oxide Nanowires

Abstract

We in situ probed the surface band bending (SBB) by ultraviolet photoelectron spectroscopy (UPS) in conjunction with field-effect transistor measurements on the incompletely depleted ZnO nanowires (NWs). The diameter range of the NWs is ca. 150–350 nm. Several surface treatments (i.e., heat treatments and Au nanoparticle (NP) decoration) were conducted to assess the impact of the oxygen adsorbates on the SBB. A 100 °C heat treatment leads to the decrease of the SBB to 0.74 ± 0.15 eV with 29.9 ± 3.0 nm width, which is attributed to the removal of most adsorbed oxygen molecules from the ZnO NW surfaces. The SBB of the oxygen-adsorbed ZnO NWs is measured to be 1.53 ± 0.15 eV with 43.2 ± 2.0 nm width. The attachment of Au NPs to the NW surface causes unusually high SBB (2.34 ± 0.15 eV with the wide width of 53.3 ± 1.6 nm) by creating open-circuit nano-Schottky junctions and catalytically …