Quantum Mechanics Calculations of the Thermodynamically Controlled Coverage and Structure of Alkyl Monolayers on Si(111) Surfaces
Abstract
The heat of formation, ΔE, for silicon (111) surfaces terminated with increasing densities of the alkyl groups CH_3- (methyl), C_2H_5- (ethyl), (CH_3)_2CH- (isopropyl), (CH_3)_3C- (tert-butyl), CH_3(CH_2)_5- (hexyl), CH_3(CH_2)_7- (octyl), and C_6H_5- (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 ΔG_S 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, ΔG_H, 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.
Additional Information
© 2006 American Chemical Society. Received: January 30, 2006; In Final Form: April 5, 2006. Publication Date (Web): July 13, 2006. E.J.N. and N.S.L. gratefully acknowledge the NSF, Grant CHE-021358, for support of this work. S.D.S. and W.A.G. thank the Microelectronics Advanced Research Corporation (MARCO) and its Focus Center on NanoEngineered Architectonics (FENA).Attached Files
Supplemental Material - jp060640+si20060405_071852.pdf
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Additional details
- Eprint ID
- 76677
- Resolver ID
- CaltechAUTHORS:20170419-102845785
- NSF
- CHE-0213589
- Microelectronics Advanced Research Corporation (MARCO)
- Focus Center on NanoEngineered Architectonics (FENA)
- Created
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2017-04-19Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field