High-temperature annealing and surface photovoltage shifts onSi(111)7×7

Abstract

The relation between annealing temperature and surface photovoltage ͑SPV͒ shifts on the Si͑111͒7 ϫ 7 surface of lightly n-doped substrates has been studied by core-level and valence-band photoelectron spectroscopies at 100 K. The SPV shift was found to depend strongly on the annealing temperature and the photon flux. Between 900 and 1150°C the magnitude of the SPV shift shows a general decrease with annealing temperature. After a narrow plateau, the SPV shift becomes positive for annealings at 1250 and 1270°C. As a consequence, the adatom surface state of the 7 ϫ 7 surface appears above the Fermi level. The unexpected SPV shift can be explained by the formation of a p-type layer during high-temperature annealing of the Si sample. The role of boron and carbon contaminations has been discussed in this context in the literature. By correlating the SPV shifts with the C 1s and B 1s core-level signals, we conclude that carbon, but not boron, is involved in the formation of the p-type layer. Further, our results show that the annealing temperature plays a crucial role when binding energies are determined from photoemission spectra at low temperature. The effect is of particular importance in the study of surface band-gap openings related to phase transitions at low temperature.

Fermi level pinning at the Ge(001) surface—A case for non-standard explanation

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Tuning the conductivity along atomic chains by selective chemisorption

“…A reasonable scenario is the formation of interstitial C defects with typical concentrations of 10 14 -10 16 cm −3 or, equivalently, less than 0.1% per ML, which act as p-type dopants [38,39,41,42].…”

Effect of surface carrier concentration on valence subbands in Si(111)p-type inversion layers: Angle-resolved photoemission spectroscopy

“…In the case of Si͑111͒7 ϫ 7 at 100 K, the S 2 surface states peak was reported to shift by 0.7 eV by changing the photon flux. 53 At room temperature, however, the carrier recombination rate is high enough and no large SPV effect is expected. 53 Dispersion structures of the valence subbands in both ILs measured by ARPES are shown in Figs.…”