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Published December 13, 2007 | public
Journal Article

High-Resolution Synchrotron Photoemission Studies of the Electronic Structure and Thermal Stability of CH_(3-) and C_2H_(5-)functionalized Si(111) Surfaces

Abstract

The relative coverage, thermal stability, and electronic properties of CH_(3-) and C_2H_(5-)functionalized Si(111) surfaces prepared by a two-step chlorination/alkylation procedure have been compared using high-resolution synchrotron photoemission spectroscopy. Whereas the CH_(3-) terminated Si(111) surface showed only one C 2s peak for the occupied σ orbitals, the C 2s spectra of C_2H_(5-)terminated Si(111) surfaces showed a symmetric splitting of the occupied σ orbitals, as expected for an ethyl moiety bonded to the surface. The C_2H_5 termination resulted in an unpinning of the Si surface Fermi level, with a band bending of ∼0.2 eV, and produced a surface dipole potential step of −0.23(15) eV. The observed close-to-flat-band condition is similar to that of CH_3−Si(111) and is consistent with H termination of the non-alkylated Si atop sites in the two-step chlorination/alkylation process. The C_2H_(5-)functionalized Si(111) surfaces decomposed at temperatures >300 °C, whereas CH_3−Si(111) surfaces were stable up to at least 440 °C. The data clearly highlight the similarities and identify some significant differences between the behavior of the CH_3- and C_2H_(5-)functionalized Si(111) surfaces.

Additional Information

© 2007 American Chemical Society. Received 2 July 2007. Published online 10 November 2007. Published in print 1 December 2007. We gratefully acknowledge the National Science Foundation, Grant No. CHE-0604894, for support of this work (N.S.L. and L.J.W.) and for providing a graduate research fellowship to L.J.W. W.J. acknowledges the traveling support of the Deutsche Forschungsgemeinschaft, DFG Grant No. JA 85910-1. The BMBF is acknowledged for support for setting up and running SoLiAS at BESSY (Contracts 05 KS1RD1/0 and 05 KS4RD1/0, R.H. and W.J.) and for travelgrants (05 ES3XBA/5). This work was also supported by the European Network of Excellence FAME, WP6.

Additional details

Created:
August 19, 2023
Modified:
October 26, 2023