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

Personal Author(s) : Bronikowski, Michael ; Hamers, Robert J.

PDF Url : ADA289218

Report Date : 20 DEC 1994

Pagination or Media Count : 24

Abstract : We have studied the room-temperature adsorption and dissociation of methyl chloride (CH3Cl) on Si(001) using Scanning Tunneling Microscopy (STM). Fragments are identified by the symmetry of their binding on the underlying Si(001) 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 Cl:CH3 ratio on the surface is found to be approximately 2:1, 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.

Descriptors :   *METHYL RADICALS, *ADSORPTION, *SILICON, *CHLORIDES, *DISSOCIATION, SCANNING, MOLECULES, CRYSTAL LATTICES, TUNNELING(ELECTRONICS), ELECTRONIC SCANNERS, RESOLUTION, VACUUM, ATOMS, STRENGTH(MECHANICS), ROOM TEMPERATURE, ELECTRON MICROSCOPY, SURFACES, CHEMICAL BONDS, RESPONSE, SYMMETRY, ORGANIC MATERIALS, ATOMIC PROPERTIES, ISLANDS, DIMERS, CHLORINE.

Subject Categories : Organic Chemistry
      Physical Chemistry
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE