An STM, AES and LEED study of the segregated sulfur on Pd(111)

First-principles study of sulfur overlayers on Pd(111) surface

“…Previous LEED and STM experiments showed that for S coverage, lower than 0.33 ML at 300 K, S atoms coalesce into two-dimensional islands with a ( p 3 · p 3) structure [19][20][21][22][23][24]26,27]. Islands with ( p 7 · p 7) and (2 · 2) structures were also detected on the Pd(1 1 1) surface [26,27].…”

“…LEED analysis and normal incidence X-ray standing wave (NIXSW) measurements show that S atoms in the ( p 3 · p 3) structure occupy threefold fcc hollow sites [22,23,25]. At elevated temperatures (400-700 K), a predominantly ( p 7 · p 7) pattern emerges [20,26,27]. At these conditions, evidence suggests that the S atoms migrate into the subsurface region.…”

“…At these conditions, evidence suggests that the S atoms migrate into the subsurface region. Published reports based on STM, scanning tunneling spectroscopy (STS) and full potential linearized augmented plane waves (FLAPW) calculations indicate that the atomic structure for the ( p 7 · p 7) phase consists of a sulfided overlayer [19,20,26,27].…”

“…Thus, the study of the structure of the adsorbed S is of crucial importance. The key model system, S adsorption on the Pd(1 1 1) surface, has been the subject of numerous experimental studies [13,[18][19][20][21][22][23][24][25][26][27]. The picture arising from these investigations is that the behavior of S on the surface is quite varied and depends markedly on the coverage and temperature.…”

“…The picture arising from these investigations is that the behavior of S on the surface is quite varied and depends markedly on the coverage and temperature. For S coverage of 0.25 ML, created at 300-350 K by exposing the Pd(1 1 1) surface to H 2 S, a ( p 3 · p 3) structure on the surface was identified by low-energy electron diffraction (LEED) [19][20][21]. The existence of this structure below 0.33 ML was suggested to be indicative of island formation.…”