The Structure of Atomic Sulfur Phases on Au(111)

Abstract

The structural phases formed by atomic sulfur on Au(111) due to reaction with molecular S2 have been investigated by qualitative low-energy electron diffraction (LEED), scanning tunneling microscopy, and normal incidence X-ray standing wavefield absorption (NIXSW) combined with X-ray photoelectron spectroscopy (XPS). Three phases are identified with increasing coverage, namely, a newly identified (5 × 5) phase, a ( × )R30° phase, and a “complex” phase. The (5 × 5) phase, with a LEED pattern having the appearance of a “split-spot” ( × )R30° pattern, is interpreted in terms of local ( × )R30° ordering within a (5 × 5) ordered domain structure. The S atoms in the (5 × 5) phase occupy fcc hollow sites 1.56 Å above the outermost extended Au(111) bulk atomic scatterer plane. A specific model of the ordering in this phase is proposed that, together with the observed marginal stability of the true, long-range-ordered, ( × )R30° phase, indicates significant short-range S−S repulsion and probably compressive surface stress. The complex phase, that coexists in a poorly ordered state with the lower coverage atomic chemisorption phases, is interpreted in terms of an incommensurate long-range periodicity, but the NIXSW data shows clear evidence of local commensuration, with the S atoms mainly close to atop sites relative to the underlying Au(111) substrate; these data provide strong support for a previously proposed model based on a sulfide layer of stoichiometry AuS.

The structure of the Au(111)/methylthiolate interface: New insights from near-edge x-ray absorption spectroscopy and x-ray standing waves

“…[14]) until a clean surface was achieved as indicated by X-ray photoelectron spectroscopy (performed with synchrotron radiation); LEED showed the characteristic splitting of the (1x1) diffracted beams associated with the (23x3)rect. 'herring-bone' reconstruction.…”

A scanning tunneling microscopy investigation of the phases formed by the sulfur adsorption on Au(100) from an alkaline solution of 1,4-piperazine(bis)-dithiocarbamate of potassium

“…Some authors have proposed the use of S 2 and SO 2 from the gas phase [29][30][31] and from electrochemical oxidation of gold surfaces in the presence of Na 2 S [32,33] in order to study sulfur/gold interactions. They have reported that sulfur is initially chemisorbed on Au(111) at the step edges.…”

“…They have reported that sulfur is initially chemisorbed on Au(111) at the step edges. Deposition of sulfur on Au(111) using gaseous S 2 shows a diluted phase of the (5 × 5) structure at a coverage of ∼0.25 ML [31], which is identified by means of low-energy electron diffraction (LEED). The sulfur is adsorbed on Au(111) from the electrochemical adsorption of the Na 2 [32].…”

New Insights into Sulfur Deposition on Gold Using Dithiobisphthalimide as a New Precursor

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Despite the considerable amount of work in this area, the nature of this interaction is still not totally understood, even with the most simple system where only sulfur is deposited on gold. [5][6][7][8][9][10][11][12][13][14][15] This is especially important considering the present debate regarding the structure of the thiolate/Au interface in self-assembled monolayers (SAMs). [4] This debate is driven by a need to understand a number of characteristics associated with SAM formation, such as the mobility of the adsorbed species leading to different phases, lifting of the Au reconstruction, production of etch pits, and adsorption site determination.…”

“…[5][6][7][8][9][10][11][12][13][14][15] The resulting modified surface at high coverage, showing rectangular structures by scanning tunneling microscopy (STM), has been interpreted in diverging ways, and conflicting models to describe it have been proposed. [5][6][7][8][9][10][11][12][13][14][15] Sulfur deposition on gold surfaces is usually achieved in aqueous electrolytic solutions using precursors, such as S 2À , SH À , and H 2 S, through spontaneous [6,7] or electrochemical [8][9][10] conditions; or in the gas phase using S 2 or SO 2 . [10] The opportunity to investigate this deposition in an organic solvent, at conditions similar to those used for SAM formation in solution, may provide helpful information in regards to the S/Au interaction.…”