AVS 47th International Symposium
    Material Characterization Tuesday Sessions
       Session MC-TuP

Paper MC-TuP26
Dynamic Force Microscopy Investigations on Molecular Structures and Electrical Properties of Organic Ultrathin Films

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: K. Kobayashi, Kyoto University, Japan
Authors: K. Kobayashi, Kyoto University, Japan
T. Fukuma, Kyoto University, Japan
H. Yamada, Kyoto University, Japan
T. Horiuchi, Kyoto University, Japan
K. Matsushige, Kyoto University, Japan
Correspondent: Click to Email
Dynamic force microscopy (DFM) was used to investigate the nanometer-scale structures and electrical properties of organic molecular films, which should be elucidated for their promising applications for molecular electronics. Frequency modulation (FM) detection method which can give high sensitivity especially in a vacuum environment was used in our DFM. The samples used in this study were organic ultrathin films such as self-assembled monolayers (SAMs) of alkanethiol molecules on Au(111) surface and fullerene crystalline islands deposited on Si(111) surface. On fullerene crystalline islands, we successfully obtained molecularly-resolved images, in which molecules were hexagonally packed. Local variation in surface potential (SP) was also mapped using Kelvin null method in DFM, which allowed us to study the local charge transfer between fullerene thin films and the substrate. In the SP image, a small contact potential difference (CPD) between the fullerene crystalline islands and monolayer-covered Si(111) surface was measured. In addition, we obtained molecularly-resolved images on both SAMs of short-chain alkanethiol molecule (octanethiol) and long-chain molecule (hexadecanethiol). The fact that the latter long-chain SAMs could not be imaged by scanning tunneling microscopy (STM) due to the poor electrical conductivity demonstrates a remarkable advantage of DFM for the studies of organic thin films.