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.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry