title: Low-temperature STM images of methyl-terminated Si(111) surfaces.
abstract: Low-temperature scanning tunneling microscopy (STM) has been used to image CH(3)-terminated Si(111) surfaces that were prepared through a chlorination/alkylation procedure. The STM data revealed a well-ordered structure commensurate with the atop sites of an unreconstructed 1 x 1 overlayer on the silicon (111) surface. Images collected at 4.7 K revealed bright spots, separated by 0.18 +/- 0.01 nm, which are assigned to adjacent H atoms on the same methyl group. The C-H bonds in each methyl group were observed to be rotated by 7 +/- 3 degrees away from the center of an adjacent methyl group and toward an underlying Si atom. Hence, the predominant interaction that determines the surface structure arises from repulsions between hydrogen atoms on neighboring methyl groups, and secondary interactions unique to the surface are also evident.
authors.affiliation: Division of Chemistry and Chemical Engineering, 127-72, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Yu
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Webb
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Ries
authors.forename: Santiago D
authors.initials: SD
authors.lastname: Solares
authors.forename: William A
authors.initials: WA
authors.lastname: Goddard
authors.forename: James R
authors.initials: JR
authors.lastname: Heath
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Lewis
mesh_terms: D006838:Hydrocarbons / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling / Q000379:methods; D010316:Particle Size; D012680:Sensitivity and Specificity; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
chemical_list: D006838:Hydrocarbons; D012825:Silicon