Thermal Behavior of Alkyl Monolayers on Silicon Surfaces

Abstract

Densely-packed alkyl monolayers similar to those previously reported by Linford et al.1,2 are formed by the reaction of 1-alkenes with hydrogen-terminated surfaces of both Si(111) and Si(100). The thermal behavior of these monolayers in vacuum has been studied using high-resolution electron energy loss spectroscopy. Both on Si(111) and on Si(100), the monolayers are found to be stable up to about 615 K. Desorption is signaled by a decrease in the intensity of C−H modes, accompanied by the appearance of Si−H modes, which suggests that desorption occurs through β-hydride elimination reactions. Upon further annealing to 785 K, C−H and Si−H modes essentially disappear, and a peak appears at 780 cm-1, which is attributed to a SiC vibrational mode. This behavior indicates that decomposition of the monolayers has taken place.