Accession Number:

ADA289218

Title:

Atomically Resolved STM study of the Adsorption and Dissociation of Methyl chloride on Si(001).

Descriptive Note:

Interim technical rept.,

Corporate Author:

WISCONSIN UNIV-MADISON DEPT OF CHEMISTRY

Report Date:

1994-12-20

Pagination or Media Count:

24.0

Abstract:

We have studied the room-temperature adsorption and dissociation of methyl chloride CH3Cl on Si001 using Scanning Tunneling Microscopy STM. Fragments are identified by the symmetry of their binding on the underlying Si001 lattice. Methyl chloride adsorbs dissociatively at room temperature, yielding a methyl group and a chlorine atom bound to the surface. Chlorine atoms bind in a variety of geometries, the most common being two chlorine atoms bonded to a single silicon dimer silicon monochloride dimers. When the surface is heated to 150 deg C, all Cl rearranges to this monochloride-type bonding configuration, and images reveal the beginnings of monochloride island formation. The ClCH3 ratio on the surface is found to be approximately 21, implying that not all methyl groups are bound to the surface in the reaction. Consideration of the relative bond strengths involved leads us to propose a reaction mechanism in which the surface sometimes abstracts a Cl atom from the CH3Cl molecule, ejecting a methyl group back into the vacuum.

Subject Categories:

  • Organic Chemistry
  • Physical Chemistry
  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE