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Origin of a surface state above the Fermi level on Ge(001) and Si(001) studied by temperature-dependent ARPES and LEED

Eriksson, P E J; Adell, Martin LU ; Sakamoto, Kazuyuki and Uhrberg, R I G (2008) In Physical Review B (Condensed Matter and Materials Physics) 77(8). p.5-085406
Abstract
Variable temperature photoemission studies in the literature have revealed the presence of a surface state above the Fermi level on clean Ge(001). We present photoemission and low energy electron diffraction results from Ge(001) obtained between 185 and 760 K. Our measurements show a peak above the Fermi level with a maximum intensity at a sample temperature of around 625 K. At higher temperatures, we observe a gradual decrease in the intensity. Angle resolved spectra show that the surface state has a (k) over bar (parallel to) dependence and is therefore not attributed to defects. Very similar results were obtained on both an intrinsic (30 Omega cm) and a 10 m Omega cm n-type sample. The overall appearance of the spectral feature is found... (More)
Variable temperature photoemission studies in the literature have revealed the presence of a surface state above the Fermi level on clean Ge(001). We present photoemission and low energy electron diffraction results from Ge(001) obtained between 185 and 760 K. Our measurements show a peak above the Fermi level with a maximum intensity at a sample temperature of around 625 K. At higher temperatures, we observe a gradual decrease in the intensity. Angle resolved spectra show that the surface state has a (k) over bar (parallel to) dependence and is therefore not attributed to defects. Very similar results were obtained on both an intrinsic (30 Omega cm) and a 10 m Omega cm n-type sample. The overall appearance of the spectral feature is found to be quite insensitive to sample preparation. Low energy electron diffraction investigations show how the sharp c(4x2) pattern becomes streaky and finally turns into a 2x1 pattern. The onset of the structure above the Fermi level takes place just before all c(4x2) streaks have disappeared which corresponds to a temperature of around 470 K. On Si(001), we also observe photoemission intensity above the Fermi level. It is weaker than on Ge(001) and appears at higher temperature. We find that the emission above the Fermi level can be explained by thermal occupation of the pi(*) band derived from a 2x1 ordering of asymmetric dimers on the surface. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review B (Condensed Matter and Materials Physics)
volume
77
issue
8
pages
5 - 085406
publisher
American Physical Society
external identifiers
  • wos:000253764300089
  • scopus:38849126715
ISSN
1098-0121
DOI
10.1103/PhysRevB.77.085406
language
English
LU publication?
yes
id
693e873c-25de-4a00-9621-67ea0fb8bd43 (old id 1185893)
date added to LUP
2008-09-03 11:10:28
date last changed
2017-10-22 04:03:22
@article{693e873c-25de-4a00-9621-67ea0fb8bd43,
  abstract     = {Variable temperature photoemission studies in the literature have revealed the presence of a surface state above the Fermi level on clean Ge(001). We present photoemission and low energy electron diffraction results from Ge(001) obtained between 185 and 760 K. Our measurements show a peak above the Fermi level with a maximum intensity at a sample temperature of around 625 K. At higher temperatures, we observe a gradual decrease in the intensity. Angle resolved spectra show that the surface state has a (k) over bar (parallel to) dependence and is therefore not attributed to defects. Very similar results were obtained on both an intrinsic (30 Omega cm) and a 10 m Omega cm n-type sample. The overall appearance of the spectral feature is found to be quite insensitive to sample preparation. Low energy electron diffraction investigations show how the sharp c(4x2) pattern becomes streaky and finally turns into a 2x1 pattern. The onset of the structure above the Fermi level takes place just before all c(4x2) streaks have disappeared which corresponds to a temperature of around 470 K. On Si(001), we also observe photoemission intensity above the Fermi level. It is weaker than on Ge(001) and appears at higher temperature. We find that the emission above the Fermi level can be explained by thermal occupation of the pi(*) band derived from a 2x1 ordering of asymmetric dimers on the surface.},
  author       = {Eriksson, P E J and Adell, Martin and Sakamoto, Kazuyuki and Uhrberg, R I G},
  issn         = {1098-0121},
  language     = {eng},
  number       = {8},
  pages        = {5--085406},
  publisher    = {American Physical Society},
  series       = {Physical Review B (Condensed Matter and Materials Physics)},
  title        = {Origin of a surface state above the Fermi level on Ge(001) and Si(001) studied by temperature-dependent ARPES and LEED},
  url          = {http://dx.doi.org/10.1103/PhysRevB.77.085406},
  volume       = {77},
  year         = {2008},
}