Chemical and electrical passivation of silicon (111) surfaces through functionalization with sterically hindered alkyl groups

E. Joseph Nemanick, Patrick T. Hurley, Bruce S. Brunschwig, Nathan S Lewis

Research output: Contribution to journalArticle

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Abstract

Crystalline Si(111) surfaces have been alkylated in a two-step chlorination/alkylation process using sterically bulky alkyl groups such as (CH3)2CH - (iso-propyl), (CH3)3C - (tert-butyl), and C6H5 - (phenyl) moieties. X-ray photoelectron spectroscopic (XPS) data in the C Is region of such surfaces exhibited a low energy emission at 283.9 binding eV, consistent with carbon bonded to Si. The C 1s XPS data indicated that the alkyls were present at lower coverages than methyl groups on CH3-terminated Si(111) surfaces. Despite the lower alkyl group coverage, no Cl was detected after alkylation. Functionalization with the bulky alkyl groups effectively inhibited the oxidation of Si(111) surfaces in air and produced low (-1) surface recombination velocities. Transmission infrared spectroscopy indicated that the surfaces were partially H-terminated after the functionalization reaction. Application of a reducing potential, -2.5 V vs Ag+/Ag, to Cl-terminated Si(111) electrodes in tetrahydrofuran resulted in the complete elimination of Cl, as measured by XPS. The data are consistent with a mechanism in which the reaction of alkyl Grignard reagents with the Cl-terminated Si(111) surfaces involves electron transfer from the Grignard reagent to the Si, loss of chloride to solution, and subsequent reaction between the resultant silicon radical and alkyl radical to form a silicon-carbon bond. Sites sterically hindered by neighboring alkyl groups abstract a H atom to produce Si - H bonds on the surface.

Original languageEnglish
Pages (from-to)14800-14808
Number of pages9
JournalJournal of Physical Chemistry B
Volume110
Issue number30
DOIs
Publication statusPublished - Aug 3 2006

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Silicon
Passivation
passivity
silicon
Photoelectrons
photoelectrons
alkylation
Alkylation
X rays
reagents
Carbon
chlorination
x rays
carbon
Chlorination
tetrahydrofuran
Chlorides
elimination
Infrared spectroscopy
electron transfer

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Chemical and electrical passivation of silicon (111) surfaces through functionalization with sterically hindered alkyl groups. / Nemanick, E. Joseph; Hurley, Patrick T.; Brunschwig, Bruce S.; Lewis, Nathan S.

In: Journal of Physical Chemistry B, Vol. 110, No. 30, 03.08.2006, p. 14800-14808.

Research output: Contribution to journalArticle

Nemanick, E. Joseph ; Hurley, Patrick T. ; Brunschwig, Bruce S. ; Lewis, Nathan S. / Chemical and electrical passivation of silicon (111) surfaces through functionalization with sterically hindered alkyl groups. In: Journal of Physical Chemistry B. 2006 ; Vol. 110, No. 30. pp. 14800-14808.
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