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Low energy photodesorption from Si(100) exposed to CO, CO2, O2, NO and SO2
A5 119
Surface Science 179 (1987) 119-131 North-Holland, Amsterdam
LOW ENERGY PHOTODESORFTION TO CO, CO,, 0,, NO AND SO, E. EKWELUNDU
and A. IGNATIEV
Department of Physics and Chemistry Houston, TX 77004, USA Received
FROM Si(100) EXPOSED
8 April 1986; accepted
University of Houston,
for publication
12 August
University Park, 1986
A Si(100) surface exposed to different doses of CO, COz, O,, NO and SO2 with and without accompanying electron beam irradiation was found to exhibit photodesorption when irradiated with photons of wavelength 200-500 nm. CO and CO, were found to be the only desorbing species when CO or CO, were adsorbed on clean silicon. NO was found to desorb from the clean surface exposed to NO, and SO was found to desorb from the clean surface exposed to SO,. The threshold energies for photodesorption for the different species were measured to be between 2.50 and 2.62 eV. The photodesorption signal was found to be linearly dependent on the incident photon flux with the yield varying from approximately 10W6 molecules/photon at X = 450 nm to approximately lo-’ molecules/photon at X = 300 nm for all the species studied. A desorption mechanism incorporating the formation of photo-holes in the surface state bands as well as in the bulk valence bands is proposed for the system.
132
Surface
ALKYL RADICAL INVOLVEMENT M.J. BOZACK,
P.A. TAYLOR,
Surface Science Center, Department Pittsburgh, PA 15260, USA Received
3 June 1986; accepted
IN SILICON SURFACE CHEMISTRY
W.J. CHOYKE
of Chemistry,
for publication
Science 179 (1987) 132-142 North-Holland, Amsterdam
*,** and J.T. YATES,
Jr.
University of Pittsburgh, 19 August
1986
The reaction of Si(lOO)-(2 X 1) with CsH, has been observed to increase with the addition of atomic hydrogen to the CsH, overlayer. The enhancement in reactivity is postulated to originate from a free radical process involving the creation of the chemisorbed propyl species. The propyl species is bound to free valencies on the Si(100). The increase in reactivity is shown in two ways. First, the thermal desorption yield of C,H, decreases with increasing exposures of atomic hydrogen to the C,H,-covered Si(100). Second, measurements of the C(KLL)/Si(LVV) Auger peak-to-peak ratio before and after thermal desorption show that more carbon remains on the surface after C,H,(ads) interaction’with H: The ability to control the reaction of a hydrocarbon molecule with a semiconductor surface has several implications for processes of chemical vapor deposition (CVD), plasma vapor deposition (PVD), and reactive ion etching (RIE).
Surface Science 179 (1987) 119-131 North-Holland, Amsterdam
LOW ENERGY PHOTODESORFTION TO CO, CO,, 0,, NO AND SO, E. EKWELUNDU
and A. IGNATIEV
Department of Physics and Chemistry Houston, TX 77004, USA Received
FROM Si(100) EXPOSED
8 April 1986; accepted
University of Houston,
for publication
12 August
University Park, 1986
A Si(100) surface exposed to different doses of CO, COz, O,, NO and SO2 with and without accompanying electron beam irradiation was found to exhibit photodesorption when irradiated with photons of wavelength 200-500 nm. CO and CO, were found to be the only desorbing species when CO or CO, were adsorbed on clean silicon. NO was found to desorb from the clean surface exposed to NO, and SO was found to desorb from the clean surface exposed to SO,. The threshold energies for photodesorption for the different species were measured to be between 2.50 and 2.62 eV. The photodesorption signal was found to be linearly dependent on the incident photon flux with the yield varying from approximately 10W6 molecules/photon at X = 450 nm to approximately lo-’ molecules/photon at X = 300 nm for all the species studied. A desorption mechanism incorporating the formation of photo-holes in the surface state bands as well as in the bulk valence bands is proposed for the system.
132
Surface
ALKYL RADICAL INVOLVEMENT M.J. BOZACK,
P.A. TAYLOR,
Surface Science Center, Department Pittsburgh, PA 15260, USA Received
3 June 1986; accepted
IN SILICON SURFACE CHEMISTRY
W.J. CHOYKE
of Chemistry,
for publication
Science 179 (1987) 132-142 North-Holland, Amsterdam
*,** and J.T. YATES,
Jr.
University of Pittsburgh, 19 August
1986
The reaction of Si(lOO)-(2 X 1) with CsH, has been observed to increase with the addition of atomic hydrogen to the CsH, overlayer. The enhancement in reactivity is postulated to originate from a free radical process involving the creation of the chemisorbed propyl species. The propyl species is bound to free valencies on the Si(100). The increase in reactivity is shown in two ways. First, the thermal desorption yield of C,H, decreases with increasing exposures of atomic hydrogen to the C,H,-covered Si(100). Second, measurements of the C(KLL)/Si(LVV) Auger peak-to-peak ratio before and after thermal desorption show that more carbon remains on the surface after C,H,(ads) interaction’with H: The ability to control the reaction of a hydrocarbon molecule with a semiconductor surface has several implications for processes of chemical vapor deposition (CVD), plasma vapor deposition (PVD), and reactive ion etching (RIE).