Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan, ROC.
ACS Nano. 2012 Nov 27;6(11):9366-72. doi: 10.1021/nn205097e. Epub 2012 Oct 26.
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.
我们通过紫外光电子能谱（UPS）结合场效应晶体管测量原位探测了不完全耗尽的氧化锌纳米线（NWs）的表面能带弯曲（SBB）。NWs 的直径范围约为 150-350nm。进行了几种表面处理（即热处理和 Au 纳米颗粒（NP）修饰），以评估氧吸附物对 SBB 的影响。100°C 的热处理导致 SBB 降低至 0.74±0.15eV，宽度为 29.9±3.0nm，这归因于从 ZnO NW 表面去除了大部分吸附的氧分子。氧吸附的 ZnO NWs 的 SBB 测量为 1.53±0.15eV，宽度为 43.2±2.0nm。Au NPs 附着在 NW 表面上通过形成开路肖特基结并催化增强电荷 O(2)吸附物的形成，导致异常高的 SBB（2.34±0.15eV，宽度为 53.3±1.6nm）。这些表面相关现象应该对所有金属氧化物纳米结构都是通用的。我们的研究通过表面工程极大地有益于基于 NW 的传感器和光电应用器件的设计。
