Core-level photoemission study of thallium adsorbed on aSi(111)−(7×7)surface: Valence state of thallium and the charge state of surface Si atoms

Abstract

, Core-level photoemission study of thallium adsorbed on a Si (111) The coverage-dependent valence state of Tl adsorbed on a Si͑111͒-͑7 ϫ 7͒ surface and the coverage dependence of the charge states of surface Si atoms have been investigated by high-resolution core-level photoelectron spectroscopy. Although two different reconstructions were observed in low-energy electron diffraction at different coverages, a ͑1 ϫ 1͒ pattern at a Tl coverage of 1 monolayer ͑ML͒ and a ͑ ͱ 3 ϫ ͱ 3͒ pattern at a coverage of 1 / 3 ML, the binding energy of the Tl 5d core-level was the same at Tl coverages up to 1 ML. Taking the valence state on a ͑1 ϫ 1͒ surface reported in the literature into account, we conclude that the valence state of Tl is 1+, and that the 6s 2 electrons of Tl are inactive as an inert pair in the Tl-Si bonding on a Si͑111͒ surface at a coverage of 1 ML and below. In the Si 2p core-level spectra, one surface component was observed on the ͑1 ϫ 1͒ surface, and three surface components were observed on the ͑ ͱ 3 ϫ ͱ 3͒ surface. The binding energies and intensities of the Si 2p surface components indicate that the charge state of the surface Si atoms on Tl/ Si͑111͒-͑1 ϫ 1͒ is the same as that of the ͑ ͱ 3 ϫ ͱ 3͒ surfaces induced by the other group III metals, but they are different on the Tl/ Si͑111͒-͑ ͱ 3 ϫ ͱ 3͒ surface.

Effect of chlorination on the TlBr band edges for improved room temperature radiation detectors

“…The Tl positions in Fig. b are indicative of Tl in TlBr and Tl in TlO , while the small feature at higher energy represents Tl metal and is consistent with the composition analysis of Tl‐rich regions. We note that the TlBr Tl positions reported in Table differ from previous experimental reports by 0.4 eV (see Table ), but these studies were not supplemented by theoretical calculations and include the uncertainty in identifying the true VBM from the XPS valence band edge .…”

Symmetry induced peculiar Rashba effect on thallium adsorbed Si(1 1 1) surfaces

“…This surface state originates from the hybridization between a single Tl 6p electron and one electron of the dangling bond of surface Si atom. (The 6s 2 electrons of the Tl atoms act as an inert pair and are inactive in the Tl-Si bonding due to the monovalent character of the Tl atoms [22,23].) This means that there is no orbital degeneracy in the observed surface-state band, and, therefore, the splittings observed at around k || = 0.5Å -1 and at around theK point are splitting between spin subbands.…”

“…Tl atoms are adsorbed on the T4 site of the (1 × 1) unreconstructed surface as shown in Fig. 1(a) [22,23], leading to a three-fold symmetric structure with mirror planes in the [1 12] this surface structure leads theK (andK ) point of the surface Brillouin zone (SBZ) to have a C 3 symmetry, a threefold symmetry without mirror plane since these points do not lie on the mirror plane ( Fig. 1(b)).…”

Nanoclusters of Group-III Metal Atoms on Si(111)-7 × 7

“…34 However, a recent core-level photoemission study on Tl adsorbed on Si(111)-7 × 7 showed that the Tl 5d core level was the same for the 1 × 1 and √ 3 × √ 3 phases, the authors concluding that there is no variable valence effect for Tl on an Si(111) surface. 35 …”