title: A scanning tunneling microscopy study of distyrylbenzene on Ag/Ge(111)-(sqr rt of 3 x sqr rt of 3)R30 degrees.
abstract: The adsorption and self-organized monolayers of trans,trans-distyrylbenzene (tt-DSB) and cis,cis-distyrylbenzene (cc-DSB) on Ag/Ge(111)-(sqr rt of 3 x sqr rt of 3)R30 degrees (Ag/Ge(111)-sqr rt of 3) were studied by low-temperature scanning tunneling microscopy (STM) in ultrahigh vacuum. tt-DSB and cc-DSB overlayers were prepared by vapor deposition at a substrate temperature of 200 K and imaged after the samples were cooled to 100 K. High-resolution images allow identification of the internal structure of individual tt-DSB molecules with three phenyl rings and their molecular arrangements on the Ag/Ge(111)-sqr rt of 3 surface. It is found that the intermolecular distance between two terminal phenyl rings in tt-DSB is about twice the lattice constant of Ag/Ge(111)-sqr rt of 3. Such a lattice match makes Ag/Ge(111)-sqr rt of 3 an ideal substrate for tt-DSB self-organization and the formation of a (3 x 1) overlayer unit cell. The structural model and the molecule registry corresponding to STM images for the adlayers of tt-DSB on Ag/Ge(111)-sqr rt of 3 are proposed and discussed. For cc-DSB adsorption on Ag/Ge(111)-sqr rt of 3, uniform molecular overlayers with two discernible molecular images corresponding to two major types of cc-DSB conformers were observed. The coexistence of multiple conformers and the mismatch of molecular dimension of cc-DSB with the substrate unit cell length limit the growth of large cc-DSB domains.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan.
authors.forename: H C
authors.initials: HC
authors.lastname: Wu
authors.forename: C-S
authors.initials: CS
authors.lastname: Tsai
authors.forename: L-W
authors.initials: LW
authors.lastname: Chou
authors.forename: Y-R
authors.initials: YR
authors.lastname: Lee
authors.forename: J C
authors.initials: JC
authors.lastname: Jiang
authors.forename: C
authors.initials: C
authors.lastname: Su
authors.forename: J-C
authors.initials: JC
authors.lastname: Lin
mesh_terms: D000327:Adsorption; D001555:Benzene Derivatives / Q000737:chemistry*; D005857:Germanium / Q000737:chemistry*; D016252:Microscopy, Scanning Tunneling / Q000379:methods*; D008958:Models, Molecular; D010316:Particle Size; D012834:Silver / Q000737:chemistry*; D013237:Stereoisomerism; D013343:Styrenes / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature
chemical_list: D001555:Benzene Derivatives; D013343:Styrenes; C507243:distyrylbenzene; D005857:Germanium; D012834:Silver