Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, United States.
Langmuir. 2011 Jan 4;27(1):179-86. doi: 10.1021/la103614f. Epub 2010 Dec 8.
Understanding the bonding of sulfur at the germanium surface is important to developing good passivation routes for germanium-based electronic devices. The adsorption behavior of ethyl disulfide (EDS) and 1,8-naphthalene disulfide (NDS) at the Ge(100)-2 × 1 surface has been studied under ultrahigh vacuum conditions to investigate both their fundamental reactivity and their effectiveness as passivants of this surface. X-ray photoelectron spectroscopy, multiple internal reflection-infrared spectroscopy, and density functional theory results indicate that both molecules adsorb via S-S dissociation at room temperature. Upon exposure to ambient air, the thiolate adlayer remains intact for both EDS- and NDS-functionalized surfaces, indicating the stability of this surface attachment. Although both systems resist oxidation compared to the bare Ge(100)-2 × 1 surface, the Ge substrate is significantly oxidized in all cases (17-57% relative to the control), with the NDS-passivated surface undergoing up to two times more oxidation than the EDS-passivated surface at the longest air exposure times studied. The difference in passivation capability is attributed to the difference in surface coverage on Ge(100)-2 × 1, where EDS adsorption leads to a saturation coverage 17% higher than that for NDS/Ge(100)-2 × 1.
了解硫在锗表面的键合对于开发基于锗的电子器件的良好钝化途径非常重要。在超高真空条件下研究了乙基二硫醚（EDS）和 1,8-萘二硫醚（NDS）在 Ge(100)-2×1 表面上的吸附行为，以研究它们的基本反应性及其作为该表面钝化剂的有效性。X 射线光电子能谱、多次内反射-红外光谱和密度泛函理论结果表明，两种分子在室温下均通过 S-S 解离吸附。在暴露于环境空气后，对于 EDS 和 NDS 功能化表面，硫醇盐吸附层保持完整，表明这种表面附着的稳定性。尽管与裸露的 Ge(100)-2×1 表面相比，两种体系都能抵抗氧化，但在所有情况下，Ge 衬底都被显著氧化（相对于对照的 17-57%），在最长的空气暴露时间内，NDS 钝化表面的氧化程度比 EDS 钝化表面高两倍。钝化能力的差异归因于 Ge(100)-2×1 上的表面覆盖率的差异，其中 EDS 吸附导致的饱和覆盖率比 NDS/Ge(100)-2×1 高 17%。
