Abstract Self-assembled monolayers (SAMs) prepared by adsorption of 4-Fluorobenzenethiol (p-FBT) and 4-Fluorobenzenemethanethiol (p-FBMT) on Au(111) substrates with different immersion times (ITs) at room temperature have been characterized using scanning tunneling microscopy (STM). The resulting p-FBT and p-FBMT monolayers showed substantial differences concerning their adlayer SAM structure and surface morphology. The structural quality of p-FBT-SAMs was found to depend significantly on the preparation conditions such as the IT. At short IT of ~3 h, the p-FBT-SAMs were found to mainly include disordered phase (α-phase) between the surrounding areas of the gold islands. With increasing IT, a gradual phase transition from the disordered phase (α) into ordered one (β-phase) was observed. Consequently, increasing the IT to ~ 24 h resulted in the formation of well-defined and highly ordered β-phase that is characterized by the commensurate ( 8 3 × 2 3 ) R 30 ∘ superstructure. In contrast to the p-FBT-SAMs, a full-coverage and close packed monolayers were formed in p-FBMT-SAMs only after very short IT of ~1 min. The upright-standing p-FBMT molecules were found to form a ( 3 × 3 ) R 3 0 ∘ structure. Despite the absence of a periodic variation in the height of the molecules within the molecular domains, we proposed a larger ( 2 3 × 3 ) R 30 ∘ unit cell containing two inequivalent p-FBMT molecules arranged in a herringbone-type structure instead of the smaller ( 3 × 3 ) R 30 ∘ unit cell. The considerable difference in the behavior of these closely related molecules which differ only in their structure (an additional methyl group between benzene and S group in p-FBMT), clarifies the delicate balance of the factors which define the energy and the structure of thiol SAMs.

中文翻译：

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烷基间隔基对 Au(111) 上 4-氟苯硫醇和 4-氟苯甲硫醇自组装单层形成和结构的影响

摘要 使用扫描仪表征了室温下不同浸泡时间 (ITs) 在 Au(111) 基底上吸附 4-氟苯硫醇 (p-FBT) 和 4-氟苯甲硫醇 (p-FBMT) 制备的自组装单分子层 (SAMs)。隧道显微镜（STM）。所得的 p-FBT 和 p-FBMT 单层在其 adlayer SAM 结构和表面形态方面表现出显着差异。发现 p-FBT-SAMs 的结构质量在很大程度上取决于制备条件，如 IT。在约 3 小时的短暂 IT 中，发现 p-FBT-SAM 主要包括金岛周围区域之间的无序相（α 相）。随着 IT 的增加，观察到从无序相 (α) 到有序相 (β 相) 的逐渐相变。最后，将 IT 增加到 ~ 24 小时导致形成明确且高度有序的 β 相，其特征在于相称的 ( 8 3 × 2 3 ) R 30 ∘ 上层结构。与 p-FBT-SAM 相比，只有在约 1 分钟的非常短的 IT 后，才能在 p-FBMT-SAM 中形成全覆盖和密堆积的单层。发现直立的 p-FBMT 分子形成 ( 3 × 3 ) R 3 0 ∘ 结构。尽管分子域内分子的高度没有周期性变化，但我们提出了一个更大的 (2 3 × 3 ) R 30 ∘ 晶胞，其中包含两个不等价的 p-FBMT 分子排列在人字形结构中，而不是较小 ( 3 × 3 ) R 30 ∘ 晶胞。