Quantum mechanics calculations of the thermodynamically controlled coverage and structure of alkyl monolayers on Si(111) surfaces

E. Joseph Nemanick, Santiago D. Solares, William A. Goddard, Nathan S. Lewis

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The heat of formation, ΔE, for silicon (111) surfaces terminated with increasing densities of the alkyl groups CH3- (methyl), C 2H5- (ethyl), (CH3)2CH- (isopropyl), (CH3)3C- (terf-butyl), CH3(CH 2)5- (hexyl), CH3(CH2) 7(octyl), and C6H5- (phenyl) was calculated using quantum mechanics (QM) methods, with unalkylated sites being H-terminated. The free energy, ΔG, for the formation of both Si-C and Si-H bonds from Si-Cl model componds was also calculated using QM, with four separate Si-H formation mechanisms proposed, to give overall ΔGs values for the formation of alkylated Si(111) surfaces through a two step chlorination/ alkylation method. The data are in good agreement with measurements of the packing densities for alkylated surfaces formed through this technique, for Si-H free energies of formation, ΔGH, corresponding to a reaction mechanism including the elimination of two H atoms and the formation of a C=C double bond in either unreacted alkyl Grignard groups or tetrahydrofuran solvent.

Original languageEnglish
Pages (from-to)14842-14848
Number of pages7
JournalJournal of Physical Chemistry B
Volume110
Issue number30
DOIs
Publication statusPublished - Aug 3 2006

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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