Thermal Stability of Self-Assembled Monolayers of n-Hexanethiol on Au(111)-(1 × 1) and Au(001)-(1 × 1)

Abstract

The thermal desorption in ultra-high vacuum of n-hexanethiol (C6T) self-assembled monolayers (SAMs) prepared from ethanolic solutions on Au(111) and Au(001) unreconstructed surfaces was investigated by X-ray photoelectron spectroscopy. The SAMs desorption was performed from room temperature (RT) to 380 K. We reported that the hexanethiolate surface saturation coverage is bigger (∼ 0.4 ML) for the SAM on Au(001) than on Au(111) (∼ 0.33 ML). We identified a greater stability for C6T SAMs on Au(001). Large amounts of physisorbed species was found on preferred oriented (111) polycrystalline Au at the low coverage regime at RT, while the SAM on the Au(001) single-crystal at this conditions desorbs at a steady pace. At 340 K, both SAMs remain stable at the coverage expected for the lying-down phases that maximizes the van der Waals interactions. We observed that at higher temperatures the carbon alpha-sulfur bond cleavages producing free S on both gold surfaces.

Mechanistic Framework for the Formation of Different Sulfur Species by Electron Irradiation of n-Dodecanethiol Self-Assembled Monolayers on Au(111) and Au(100)

“…In good agreement with previous reports, the S2 has a BE of 162.05 eV for DDT on Au(111), 63 while it is 161.85 eV for Au(100). 35,37,66 According to Arisnabarreta et.al. this BE shift is associated with a larger electronic charge transfer from the Au to the S in the case of the (100) surface.…”

Understanding metal organic chemical vapour deposition of monolayer WS2: the enhancing role of Au substrate for simple organosulfur precursors

“…This is consistent with the known strong chemisorption of organosulfides on Au and their favourable dissociation on Au reported in heterogeneous catalysis literature. [40][41][42] There are a range of possible competing reactions including W carbide formation. 62 Our operando XPS data highlights that although the sulfidation of W is self-limiting, the deposition of a-C contamination and formation of tungsten carbide proceeds with ongoing DMS exposure (Fig.…”

“…39 There is a large body of literature on the absorption of thiols or disulfides onto Au, forming self-assembled monolayers, including reports of dissociation of organosulfides on Au. [40][41][42] This motivates us here to explore the use of Au in conjunction with DMS as sulfidation agent for MOCVD of WS 2 layer growth. We find that the Au substrate allows a significant reduction in the DMS pressure required to nucleate and grow WS 2 by MOCVD.…”

Thermal Stability of Alkanethiolate and Aromatic Thiolate Self-Assembled Monolayers on Au(111): An X-ray Photoelectron Spectroscopy Study

“…The thermal stability certainly depends on the identity of the SAM-forming molecules, the parameters of their self-organization, and the substrate. ,− This issue can be addressed from different viewpoints. First, the effect of temperature can be monitored by temperature-programmed desorption (TPD), which gives information about the desorption kinetics, characteristic activation energies, and character of desorbed species. , Second, temperature-induced changes can be monitored with molecular precision by scanning tunneling microscopy exposing consecutive structural modifications. − Third, a particular parameter of a SAM, such as the contact angle, molecular orientation, structural order, etc., can be monitored, as a fingerprint of temperature-induced changes. ,,, Finally, the reaction of a SAM to temperature variation can be traced by spectroscopic techniques, providing insight into the underlying processes. ,,,− …”