Snapshots of Crystal Growth: Nanoclusters of Organic Conductors on Au(111) Surfaces
Technical rept. no. 2, 1 May 1993-30 Jun 1994
MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
Pagination or Media Count:
Mono- and multilayer crystalline nanoclusters of tetra-hiafulvalene- tetracyanoquinodimethane TTF TCNO, a low-dimensional organic conductor in the bulk form, can be formed readily on Au111 surfaces by vapor phase sublimation under ambient conditions. Scanning tunneling microscopy of monolayer TTFTCNQ films reveals a two-dimensional density of states DOS that is consistent with the arrangement of TTF and TCNO molecules in the ac face of bulk TTFTCNO, in which the molecular planes are nearly parallel to the Au111 substrate. In contrast, clusters with thicknesses corresponding to two or three molecular layers exhibit a transformation to a highly anisotropic DOS that can be attributed to interlayer molecular overlap in segregated TTF and TCNQ molecular chains along the c-axis, which can be described as molecular wires. The orientation of the crystalline TTFTCNO clusters is preserved throughout the crystal growth sequence, leading to meso- and macroscopic TTFTCNO needles that are oriented perpendicular to the Au111 substrate. These studies provide visualization of crystal growth from the initial stages of nucleation to macroscopic crystals, and a Organic Conductors, Atomic Force Microscopy, Nucleation, Fractals.
- Organic Chemistry
- Physical Chemistry
- Electricity and Magnetism