Direct determination of absolute monolayer coverages of chemisorbed C2H2 and C2H4 on Si(100)

Abstract

A convenient kinetic uptake method has been employed to determine the absolute saturation monolayer coverage of C2H2 and C2H4 on a Si(100)(2×1) surface. Such measurements are important for postulating the structure of the chemisorbed hydrocarbon species on this surface. The saturation surface coverage for both chemisorbed molecules at 105 K is 2.5(±0.2)×1014 molecules/cm2 . This number is consistent with 1 hydrocarbon molecule per Si dimer site at monolayer coverage when the role of surface defects on Si(100) is considered. A di-σ bonding model for both molecules is proposed at saturation coverage.

Hydrocarbon surface chemistry on Si(100)

“…The ultrahigh vacuum (UHV) system (with a base pressure of 1 x 10-10 Torr) and the Si(100) crystal preparation have been described previously [12][13][14][15][16]; selected aspects will be summarized here. The system is equipped with an Auger electron spectrometer, an argon ion sputtering gun, a collimated and calibrated microcapillary array doser [21], and a multiplexed quadrupole mass spectrometer (QMS) with capabilities for both random flux and line-of-sight detection (22].…”

“…Heating of the For the adsorption of molecular species, a calibrated microcapillary array doser was used to deliver the gas molecules onto the Si(100) surface [21]. The doser contains an internal pinhole aperture (2 Am diameter) whose conductance has been calibrated accurately for the molecular species to be studied [12]. The partial pressure change of the molecular onto the crystal surface is determined from the calibrated conductance through the internal pinhole aperture [12] and from the calculated angular distribution of the beam [24].…”

“…The hydrocarbon species studied in this work include acetylene (C 2 H 2 ) [12,15] The methyl radical is also generally considered as an active species for carbon deposition using plasma sources as well as in high temperature CVD reactors [9,11]. Our investigations of the thermal behavior of CH 3 (a) on Si(100)…”

“…This indicates that the methyl group is an efficient source of surface carbon by thermal decomposition. This paper is a review of our investigations of the interaction of various hydrocarbon species with the Si(100) surface [12][13][14][15][16][17]. It is known that the reconstructed Si(100) surface consists of parallel rows of Si 2 dimers with one dangling bond on each surface Si atom.…”

First-principles study of the adsorption ofC2H2andCho1, Kleinman2, Chan3 et al. 2001Phys. Rev. B51250View full textAdd to dashboardCite

“…However, an ultraviolet photoemission spectroscopy study with the kinetic uptake method determined the saturation coverage to be ϭ1 ML. [14][15][16] In this work we study the adsorption of both C 2 H 2 and C 2 H 4 molecules on Si͑100͒ for coverages of ϭ0.5 and 1 ML, using the same first-principles calculation scheme. 17,18 Here the equilibrium geometries and energetics of the three existing models, i.e., dimerized, dimer-cleaved, and tetramodels, are considered.…”