title: 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 enhancing the formation of the charge O(2) adsorbates. These surface-related phenomena should be generic to all metal oxide nanostructures. Our study is greatly beneficial for the NW-based device design of sensor and optoelectronic applications via surface engineering.
authors.affiliation: Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan, ROC.
authors.forename: Cheng-Ying
authors.initials: CY
authors.lastname: Chen
authors.forename: Jose Ramon Duran
authors.initials: JR
authors.lastname: Retamal
authors.forename: I-Wen
authors.initials: IW
authors.lastname: Wu
authors.forename: Der-Hsien
authors.initials: DH
authors.lastname: Lien
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Chen
authors.forename: Yong
authors.initials: Y
authors.lastname: Ding
authors.forename: Yu-Lun
authors.initials: YL
authors.lastname: Chueh
authors.forename: Chih-I
authors.initials: CI
authors.lastname: Wu
authors.forename: Jr-Hau
authors.initials: JH
authors.lastname: He
mesh_terms: D055119:Elastic Modulus; D008422:Materials Testing / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D013499:Surface Properties; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D015034:Zinc Oxide