Reactions of atomic hydrogen with the Si(111) (7×7) surface by high resolution electron energy loss spectroscopy

Publisher Website
Google Scholar
Abstract
High resolution electron energy loss spectroscopy (vibrational and electronic excitations) and monochromatic low-energy electron diffraction (LEED) have been applied to the study of atomic-hydrogen adsorption on the Si(111) (7×7) surface at ∼300 K. Adsorbed states of hydrogen are differentiated by taking the vibrational loss spectra of the Si(111) surface exposed to various amounts of hydrogen and of the same surface subsequently heated to high temperatures. The existence of four adsorbed states is proposed. Hydrogen adsorption is considered to proceed as follows. In the very early stage (fractional hydrogen coverage θ≲0.3), the SiH species are produced by the covalent bond formation of hydrogen atoms with the dangling bonds of the Si(111) surface atoms. Then, the Si–Si bond breaking and the desorption of SiH4 and, possibly, SiH3 occur, and the corrosion-induced SiH (with the bond axes parallel to and away from the surface-normal direction), SiH2, and SiH3 species are also produced. The hydrogen coverage is saturated at θ∼1.5, where the amount of the SiH2 and SiH3 species formed is estimated to be <1/4 of that of the total SiH species. The electronic transition associated with the SiH species is observed at 9.1 eV for low hydrogen exposure, which is shifted to lower energy by the increase in the exposure. Corrosion-induced surface roughening is reflected in the high background and in the degradation of the 1/7 order beam intensities of LEED angular profiles. Patch formation of the SiH, SiH2, and SiH3 species is evident from the slow decay of the 1/7 order beam intensities.

This publication has 27 references indexed in Scilit: