Traub Matthew C, Biteen Julie S, Brunschwig Bruce S, Lewis Nathan S
Division of Chemistry and Chemical Engineering, 210 Noyes Laboratory, 127-72, Beckman Institute and Kavli Nanoscience Institute, California Institute of Technology, 1200 E. California Boulevard, Pasadena, California 91125, USA.
J Am Chem Soc. 2008 Jan 23;130(3):955-64. doi: 10.1021/ja076034p. Epub 2008 Jan 3.
The effective use of nanocrystalline semiconductors requires control of the chemical and electrical properties of their surfaces. We describe herein a chemical functionalization procedure to passivate surface states on GaAs nanocrystals. Cl-terminated GaAs nanocrystals have been produced by anisotropic etching of oxide-covered GaAs nanocrystals with 6 M HCl(aq). The Cl-terminated GaAs nanocrystals were then functionalized by reaction with hydrazine or sodium hydrosulfide. X-ray photoelectron spectroscopic measurements revealed that the surfaces of the Cl-, hydrazine-, and sulfide-treated nanocrystals were As-rich, due to significant amounts of As0. However, no As0 was observed in the photoelectron spectra after the hydrazine-terminated nanocrystals were annealed at 350 degrees C under vacuum. After the anneal, the N 1s peak of hydrazine-exposed GaAs nanocrystals shifted to 3.2 eV lower binding energy. This shift was accompanied by the appearance of a Ga 3d peak shifted 1.4 eV from the bulk value, consistent with the hypothesis that a gallium oxynitride capping layer had been formed on the nanocrystals during the annealing process. The band gap photoluminescence (PL) was weak from the Cl- and hydrazine- or sulfide-terminated nanocrystals, but the annealed nanocrystals displayed strongly enhanced band-edge PL, indicating that the surface states of GaAs nanocrystals were effectively passivated by this two-step, wet chemical treatment.
纳米晶半导体的有效利用需要控制其表面的化学和电学性质。我们在此描述一种化学功能化程序，用于钝化砷化镓纳米晶体上的表面态。通过用6 M盐酸水溶液对氧化覆盖的砷化镓纳米晶体进行各向异性蚀刻，制备了氯端基化的砷化镓纳米晶体。然后，氯端基化的砷化镓纳米晶体通过与肼或氢硫化钠反应进行功能化。X射线光电子能谱测量表明，由于存在大量的As0，氯、肼和硫化物处理的纳米晶体表面富含砷。然而，在肼端基化的纳米晶体在真空下350℃退火后，光电子能谱中未观察到As0。退火后，肼暴露的砷化镓纳米晶体的N 1s峰向结合能低3.2 eV处移动。这种移动伴随着一个Ga 3d峰的出现，该峰相对于体相值向低1.4 eV处移动，这与在退火过程中纳米晶体上形成了氮氧化镓覆盖层的假设一致。氯、肼或硫化物端基化的纳米晶体的带隙光致发光（PL）较弱，但退火后的纳米晶体显示出带边PL的强烈增强，表明通过这种两步湿化学处理有效地钝化了砷化镓纳米晶体的表面态。
