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

Fingerprint

Quantum theory
quantum mechanics
Monolayers
Free energy
Chlorination
free energy
Alkylation
Silicon
chlorination
packing density
alkylation
heat of formation
energy of formation
tetrahydrofuran
elimination
Atoms
methylidyne
silicon
atoms

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Quantum mechanics calculations of the thermodynamically controlled coverage and structure of alkyl monolayers on Si(111) surfaces. / Nemanick, E. Joseph; Solares, Santiago D.; Goddard, William A.; Lewis, Nathan S.

In: Journal of Physical Chemistry B, Vol. 110, No. 30, 03.08.2006, p. 14842-14848.

Research output: Contribution to journalArticle

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