Buildup and structure of theInSe∕Ptinterface studied by angle-resolved photoemission and x-ray absorption spectroscopy

Abstract

The atomic structure and the electronic nature of the $\mathrm{In}\mathrm{Se}∕\mathrm{Pt}$ interface have been studied by x-ray absorption spectroscopy and angle-resolved photoemission, respectively. By these measurements, it has been found that Pt atoms equally incorporate into two trigonal-prismatic intralayer positions existing within the InSe layer, although, at low Pt coverage, Pt atoms seem to prefer one of these sites, where they have a lower interaction with Se atoms. The atomic structure of the $\mathrm{In}\mathrm{Se}∕\mathrm{Pt}$ interface appears to determine its electronic behavior as Pt deposition increases. At initial stages of Pt diffusion, isolated Pt atoms act as a surface acceptor which turns the interface into intrinsic. Beyond a certain submonolayer Pt coverage, Pt-InSe reaction gives rise to localized states within the InSe band gap coming from the InSe valence band maximum. These states appear to mostly determine the $\mathrm{In}\mathrm{Se}∕\mathrm{Pt}$ barrier height before the onset of metallization expected by the formation of a bulklike Pt layer. As a result, the atomic structure of the $\mathrm{In}\mathrm{Se}∕\mathrm{Pt}$ interface has appeared to be quite far from that expected for an ideal $\mathrm{In}\mathrm{Se}∕\mathrm{Pt}$ interface and the formation of a final bulk-like Pt layer scarcely contributes to the electron barrier height at the interface. Nevertheless, the final $\mathrm{In}\mathrm{Se}∕\mathrm{Pt}$ barrier height appears to be that expected for an abrupt $\mathrm{In}\mathrm{Se}∕\mathrm{Pt}$ Schottky interface.