A study of the surface structure of deposited Au on Pb film

Abstract

Using low-temperature scanning tunnelling microscopy/scanning tunnelling spectroscopy and in situ reflection high-energy electron diffraction, the surface structure of deposited Au on Pb film was investigated. We observed two types of Moiré patterns, the first is formed by Au 2 Pb with Pb(111) √ 3 × √ 3 reconstruction (Pb-√ 3) with an average period of 2.4 nm; the second is formed by AuPb 2 with a Pb-√ 3 layer with an average period of 5.8 nm. Such a surface structure changes the boundary condition of electrons confined in the Pb film. Moreover, using the structural model proposed, it consumes three monolayers (3 ML) of Pb and reduces the film thickness. These results explain well the phase shift in the oscillation of physical properties of the Pb film, which strongly depends on film thickness by the quantum size effect.

Significantly enhanced giant Rashba splitting in a thin film of binary alloy

“…However, the LEED pattern, shown in figure 3(c), is more pronounced in the sense that it exhibits satellite Moiré spots around each alloy spot. Such Moiré patterns were observed from previous microscopic study [15,16]. Therefore, we argue that the Ge(111) substrate and even the quantum well states of Pb films are not relevant to the unique electronic structures of PbAu alloy we observe.…”

“…Figure 5(b) presents the corresponding top view of the lattice structure of the sandwiched model for PbAu alloy in the relaxed form. The Pb:Au ratio of the middle PbAu-alloy layer is 2:1 according to the preceding results [15,16]. The centered Au atom, represented by the gold ball, of each hexagonal unit corresponds to the alloy structure × 3 3R30°(5.7 Å) observed with LEED.…”

“…3 Au,consistent with our result in figure 1(d), in which the LEED spots remain the same except for those that vanish from the underlying Pb films after further Au atoms (2 Å) are deposited. However, the Moiré patterns were clearly observed in microscopic images [15,16] to reflect the strain effects from the top × − 3…”

“…We have generated thin films of binary alloy of heavy-metal atoms, PbAu alloy, on Pb films grown on Ge(111). The similar PbAu alloys were formed on Pb films grown on Si(111) and studied microscopically [15,16]. However, the focus was on the morphologies, lattice structures, and stoichiometric composition.…”

Influence of quantum well states on the formation of Au–Pb alloy in ultra-thin Pb films

“…When 2 ML Au was deposited on a global Pb film at room temperature, two types of moiré patterns were reported on the surface of Pb film; the first is formed by Au 2 Pb with an average period of 2.4 nm and the second is formed by AuPb 2 with an average period of 5.8 nm [37]. In our experiment, on the other hand, 0.2 ML Au was deposited on a Pb mesa containing many consecutive thicknesses at low temperature (90 K) and the moiré pattern showed very different average period of 7 nm (roughly 20 times the surface lattice constant of Pb (111)).…”