Final-state pseudopotential theory for the Ge 3dcore-level shifts on the Ge/Si(100)-(2×1) surface

Abstract

We have calculated the Ge 3d core-level shifts on the Ge/Si(100)-(2X 1) surface using the final-state pseudopotential theory. We find that the core levels of the up and down atoms within the asymmetric Ge dimer are separated by 0.54 eV at 1-ML Ge coverage, 0.43 eV at 2-ML Ge coverage, and 0.40 eV at the clean Ge(100) surface. Such a large core-level shift represents a substantial charge asymmetry within the Ge dimer. The present results agree well with recent x-ray photoemission spectroscopy (XPS) data on the Ge(100) surface, but disagree with XPS data on the adsorbed Ge/Si(100) surface.

Scanning Tunneling Microscopy Identification of Atomic-Scale Intermixing on Si(100) at Submonolayer Ge Coverages

“…This conclusion is consistent with the expectation we start with, based on comparison between clean Ge(l 00) and Si(l 00) STS results [11,12], that Ge dimers appear brighter than substrate Si dimers. Although a larger asymmetry for Ge dimers on Si(l 00) than for Ge dimers on Ge(100) has also been calculated [25], such an asymmetry simply leads to more charge transfer from down-ends of the Ge dimers to the up-ends, making for even greater visibility of Ge in low-bias empty-state imagjng. If intermixing results in a Ge-Si mixed dimer, we need to consider whether in this case the dimer is still bfighter than a substrate Si dimer.…”

Density functional theory calculations of continuum lowering in strongly coupled plasmas

“…The highly charged ions needed for plasma charge state calculations are constructed by creating excited-electron configurations in inner atomic shells and freezing them in the core of the potential. The use of excited potentials in DFT calculations to study the electronic structure, often investigated experimentally by photoemission spectroscopy, is an established technique [22][23][24][25] , and has been recently adapted to the frozen-core PAW formalism to study the properties of dense plasmas 26 . This technique has since been successfully applied to interpret XANES measurements on dense Al plasmas with a 1s core hole 27 , and to the study of X-ray emission spectroscopy and electronic structure of L-shell-excited Al on the VUV FEL FLASH 28 .…”

Effect of hydrogenation on the adsorption ofGeonSi(001)

“…4,6 The lowest-energy configuration for the 0.5 ML coverage was achieved when the Ge atom was in the top layer and occupied the up-atom site of the mixed dimer ͑nondiffused͒. 12,15 This is also true in our calculations: we find that the total energy of the system increases by 0.25 eV/dimer when the Ge atom is interdiffused into the second layer. Our result for this energy difference is very similar to the result obtained in the works of Cho et al, who obtained 0.23 eV/dimer ͑Ref.…”

“…9,[12][13][14][15] The general consensus is that the Ge-nondiffused ͑i.e., the mixed Ge-Si dimer structure on the surface layer͒ is energetically more favorable than structures with Ge interdiffused into deeper surface layers. To our best knowledge, the only theoretical work regarding the energetics of Ge deposition on hydrogenated Si͑001͒ surface has been carried out by Rudkevich et al 9 However, this work only provides a limited amount of information on the energetics of a place exchange between Ge and Si on the hydrogenated surface with 1 ML deposition of Ge.…”