Chemical stability towards O2 and H2O of Si(111) grafted with -CH3, -CH2CH2CH3, -CHCHCH3 and -CCCH3.

F. A. SORIA; P. PAREDES OLIVERA; PATRITO, E. MARTIN

AMER CHEMICAL SOC

Lugar: Washington; Año: 2015 vol. 119 p. 284 - 284

he chemical stability of compact monolayers on silicon toward oxidizing agents is a key issue for the use of such monolayers in devices such as solar cells or in the electronics industry. In this work, we investigated the reactivity toward H2O, O2, and OH species of monolayers terminated with a methyl group to unveil the mechanisms that prevent the oxidation of the underlying silicon. Density functional theory calculations were performed to investigate the reaction pathways for the two competing processes involved: diffusion through the monolayer and reaction with the terminal methyl group. Activation energy barriers for the diffusion of H2O and O2 are very sensitive to the monolayer structure, and they increase in the order -CH2-CH2-CH3 < -C-C-CH3 < -CH-CH-CH3 with energy barriers of 0.0 kcal/mol (0.0 kcal/mol), 35.0 kcal/mol (42.5 kcal/mol), and 57.0 kcal/mol (64.1 kcal/mol), respectively, for H2O (O2). This agrees with ordering of stabilities reported experimentally for these monol