Probing surface band bending of surface-engineered metal oxide nanowires

Cheng Ying Chen, Jose Ramon Duran Retamal, I. Wen Wu, Der Hsien Lien, Ming Wei Chen, Yong Ding, Yu Lun Chueh, Chih I. Wu, Jr Hau He*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

147 Scopus citations


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 O2 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.

Original languageEnglish
Pages (from-to)9366-9372
Number of pages7
JournalACS Nano
Issue number11
StatePublished - 27 Nov 2012


  • Schottky junction
  • ZnO
  • metal oxide
  • nanowire
  • oxygen vacancy
  • surface band bending


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