Measurement of the band bending and surface dipole at chemically functionalized Si(111)/vacuum interfaces

David C. Gleason-Rohrer, Bruce S. Brunschwig, Nathan S Lewis

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

The core-level energy shifts observed using X-ray photoelectron spectroscopy (XPS) have been used to determine the band bending at Si(111) surfaces terminated with Si-Br, Si-H, and Si-CH3 groups, respectively. The surface termination influenced the band bending, with the Si 2p3/2 binding energy affected more by the surface chemistry than by the dopant type. The highest binding energies were measured on Si(111)-Br (whose Fermi level was positioned near the conduction band at the surface), followed by Si(111)-H, followed by Si(111)-CH3 (whose Fermi level was positioned near midgap at the surface). Si(111)-CH3 surfaces exposed to Br2(g) yielded the lowest binding energies, with the Fermi level positioned between midgap and the valence band. The Fermi level position of Br2(g)-exposed Si(111)-CH3 was consistent with the presence of negatively charged bromine-containing ions on such surfaces. The binding energies of all of the species detected on the surface (C, O, Br) shifted with the band bending, illustrating the importance of isolating the effects of band bending when measuring chemical shifts on semiconductor surfaces. The influence of band bending was confirmed by surface photovoltage (SPV) measurements, which showed that the core levels shifted toward their flat-band values upon illumination. Where applicable, the contribution from the X-ray source to the SPV was isolated and quantified. Work functions were measured by ultraviolet photoelectron spectroscopy (UPS), allowing for calculation of the sign and magnitude of the surface dipole in such systems. The values of the surface dipoles were in good agreement with previous measurements as well as with electronegativity considerations. The binding energies of the adventitious carbon signals were affected by band bending as well as by the surface dipole. A model of band bending in which charged surface states are located exterior to the surface dipole is consistent with the XPS and UPS behavior of the chemically functionalized Si(111) surfaces investigated herein.

Original languageEnglish
Pages (from-to)18031-18042
Number of pages12
JournalJournal of Physical Chemistry C
Volume117
Issue number35
DOIs
Publication statusPublished - Sep 5 2013

Fingerprint

Vacuum
dipoles
vacuum
Binding energy
Fermi level
binding energy
Ultraviolet photoelectron spectroscopy
Core levels
photoelectron spectroscopy
ultraviolet spectroscopy
photovoltages
X ray photoelectron spectroscopy
Bromine
Electronegativity
Surface measurement
Chemical shift
Surface states
Valence bands
Surface chemistry
Conduction bands

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Measurement of the band bending and surface dipole at chemically functionalized Si(111)/vacuum interfaces. / Gleason-Rohrer, David C.; Brunschwig, Bruce S.; Lewis, Nathan S.

In: Journal of Physical Chemistry C, Vol. 117, No. 35, 05.09.2013, p. 18031-18042.

Research output: Contribution to journalArticle

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