Titration of submonolayer Au growth on Si(111)

Abstract

We study and analyze the growth of submonolayers of Au on Si(111) by a complementary set of surface techniques. Specifically, we focus on the 5 × 2 and the α √ 3 × √ 3 structures. We determine the gold coverage of these structures as a function of temperature by means of low energy electron diffraction (LEED) and low energy electron microscopy (LEEM). These results are independently calibrated by ex-situ ion scattering experiments. This allows us to present a phase diagram for this system. Remarkably, for all temperatures considered (820-1040 K), we find a coverage for the 5 × 2 phase that is significantly (≈10%) higher than the value of 0.6 monolayers which is assumed in the latest structural models. Therefore, a further refinement of the present picture of the quasi-one-dimensional 5 × 2 structure is required.

Identification of the Au Coverage and Structure of theAu/Si(111)−(5×2)Surface

“…Figure 1(a) shows the best structural model so far, proposed by a combined theoretical-experimental study of Erwin, Barke, and Himpsel (hereafter, EBH) in 2009 [25]. It features a Si honeycomb chain and an Au triple chain and contains six Au atoms and twelve top-layer Si atoms in a 5×2 unit cell, well reflecting the experimental estimations of 5.6-6.7 Au atoms [17][18][19] and 11-14 Si atoms [28,29]. The EBH model was recently challenged by a new model derived by Abukawa and Nishigaya (hereafter, AN) in a reflection high-energy electron diffraction (RHEED) study [26].…”

“…The incorporation of one more Au atom is not only a simple way of transforming into a desirable 5×2 structure but also could possibly be a physical realization of the idea of electron doping given by EBH. The resulting seven Au atoms per 5×2 cell, which is referred to as 0.7 ML, is slightly out of the experimental estimations of 0.56-0.67 ML [17][18][19] but is worth examining in light that a higher calibration of 0.65-0.67 ML is the latest result of a low-energy electron diffraction and microscopy study [19]. Figure 1(b) shows the lowest-energy structure where the added Au atom prefers to adsorb on a hollow site between the 1st and 2nd Au rows with at least 0.62 eV more gain in adsorption energy than other sites.…”

“…Its atomic structure, however, is not yet solved in spite of extensive experimental studies [8][9][10][11][12][13][14][15][16][17][18][19] and density functional theory (DFT) calculations [20][21][22][23][24][25]. This long-standing surface science problem is thus considered a touchstone of our ability to look into the structure of complex surface/nano systems at truly atomic scale.…”

“…Bc, 73.20.At, 81.07.Vb The Au/Si(111)-5×2 surface is a representative selforganized one-dimensional (1D) metal chain system [1][2][3][4] and has served as a rich source of intriguing 1D phenomena such as atomic-scale Schottky barriers [5], 1D domain-wall hoppings [6], and confined doping on a metallic chain [7]. Its atomic structure, however, is not yet solved in spite of extensive experimental studies [8][9][10][11][12][13][14][15][16][17][18][19] and density functional theory (DFT) calculations [20][21][22][23][24][25]. This long-standing surface science problem is thus considered a touchstone of our ability to look into the structure of complex surface/nano systems at truly atomic scale.…”

Differential reactivity of alkanethiols with Si(111)–Au 2D surface alloys

“…The advantage of using this surface alloy over a bulk system is that the number of gold atoms that can participate in SAM formation is known and fixed. At the temperature of our experiments there is no Au desorption or diffusion into the bulk, resulting in a constant Au content [14].…”