- TITLE:
- Reactivity of Fluorinated Si(100) with F2
- AUTHORS:
- Pullman, D.P.; Dept. of Chem., SDSU, San Diego, CA, USA; Tsekouras, A.A.; Dept. of Chem., UoA, Athens, Greece; Li, Y.L.; Yang, J.J.; Tate, M.R.; Gosalvez, D.B.; Laughlin, K.B.; Schulberg, M.T.; Ceyer, S.T.; Dept. of Chem., MIT, Cambridge, MA, USA
- PUBLICATION:
- Journal of Physical Chemistry B, vol.105, no.2, p. 486-496, 18 January 2001 46 Refs.
- ABSTRACT:
- The dissociative chemisorption of
F2 on the Si(100)(2 x 1) surface saturated with 1 monolayer
(ML) of fluorine is investigated as a function of the incident
F2 translational energy. At energies below 3.8 kcal/mol, no
reaction with the Si-Si bonds occurs. Above this threshold, the
probability of dissociative chemisorption rises linearly with the
normal component of the incident translational energy up to a value of
3.6 x 10-3 at 13 kcal/mol. The relatively small effect of
translational energy implies a late barrier in the potential energy
surface for the interaction of F2 with the Si-Si bonds.
These probabilities are measured by exposing the fluorine-saturated
surface to supersonic F2 beams of variable energy, followed
by thermal desorption measurements to determine the resulting fluorine
coverage. Information regarding the specific Si-Si site (Si-Si dimer or
Si-Si lattice bonds) at which the translationally activated reaction
occurs is obtained from He diffraction measurements. The intensity of
the diffracted beams is monitored after exposing the fluorine-saturated
surface to F2 of variable energy. The intensities remain
constant after exposure to low-energy (<3.8 kcal/mol) F2,
whereas they decline monotonically as a function of F2
normal energy above the 3.8 kcal/mol threshold. Moreover, the
similarity of the relative cross sections for diffusive scattering
measured after exposure to translationally fast F2 to those
measured after Ar+ ion bombardment strongly suggests that
the reaction does not occur preferentially at the Si-Si dimer bonds,
which are the weakest Si-Si bonds in the system. Reaction at Si-Si
lattice bonds also occurs, leading to surface disorder. Additional data
show that for submonolayer coverages generated from low energy
F2, no reaction with Si-Si bonds occurs, while exposure to
high-energy F2 leads to reaction with Si-Si bonds.