Abstract The adsorption of S on Si(111)- 7 × 7 has been investigated for different preparation schemes and parameters. S was supplied from an electrochemical Ag2S cell. For room temperature adsorption and subsequent annealing, no ordered S induced reconstruction can be observed with spot profile analysis low-energy electron diffraction (SPALEED). S deposition at temperatures above about 400 ∘C, however, leads to a well-ordered reconstruction. Judging from the LEED pattern, the same reconstruction was already observed by Metzner et al. [Surf. Sci. 377–379 (1997) 71–74] who identified it as 4 × 4 reconstruction. The upper temperature limit for the preparation of this superstructure depends on S flux, which is needed to compensate for desorption. Prolonged S exposure leads to surface roughening, as observed with SPALEED and scanning tunneling microscopy (STM), pointing to surface etching by S. From our SPALEED data, we can conclude that the observed reconstruction is not a 4 × 4 reconstruction, but a ( 2 0 1 2 ) superstructure with a rectangular unit cell that exists in three rotational domains, as confirmed by STM. Different structural trial models have been assessed with density functional theory. Among these model structures, a configuration with dimers adsorbed on bridging sites, with a S coverage of 1 monolayer, is most likely, since it is energetically favorable and is in agreement with all experimental results.

中文翻译：

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硫在 Si(111) 上的吸附

摘要 针对不同的制备方案和参数，研究了 S 在 Si(111)- 7 × 7 上的吸附。S 由电化学 Ag2S 电池提供。对于室温吸附和随后的退火，使用点分布分析低能电子衍射 (SPALEED) 无法观察到有序的 S 诱导重建。然而，S 在高于约 400 ∘C 的温度下沉积会导致有序的重建。从 LEED 模式来看，Metzner 等人已经观察到了相同的重建。[冲浪。科学。377–379 (1997) 71–74] 将其确定为 4 × 4 重建。制备这种上层结构的温度上限取决于 S 通量，这是补偿解吸所需的。长时间暴露于 S 导致表面粗糙，如用 SPALEED 和扫描隧道显微镜 (STM) 观察到的，指向 S 的表面蚀刻。从我们的 SPALEED 数据，我们可以得出结论，观察到的重建不是 4 × 4 重建，而是 ( 2 0 1 2 ) 上层结构STM 证实存在于三个旋转域中的矩形晶胞。已使用密度泛函理论评估了不同的结构试验模型。在这些模型结构中，最有可能是二聚体吸附在桥接位点上，S 覆盖为 1 个单层，因为它在能量上是有利的，并且与所有实验结果一致。但是 (2 0 1 2 ) 上层结构具有矩形晶胞，存在于三个旋转域中，如 STM 所证实。已使用密度泛函理论评估了不同的结构试验模型。在这些模型结构中，最有可能是二聚体吸附在桥接位点上，S 覆盖为 1 个单层，因为它在能量上是有利的，并且与所有实验结果一致。但是 (2 0 1 2 ) 上层结构具有矩形晶胞，存在于三个旋转域中，如 STM 所证实。已使用密度泛函理论评估了不同的结构试验模型。在这些模型结构中，最有可能是二聚体吸附在桥接位点上，S 覆盖为 1 个单层，因为它在能量上是有利的，并且与所有实验结果一致。