AVS 50th International Symposium
    Surface Science Wednesday Sessions
       Session SS+OF-WeA

Paper SS+OF-WeA2
Pentacene Thin Films on Clean and Chemically Modified Si(001) Surfaces

Wednesday, November 5, 2003, 2:20 pm, Room 327

Session: Growth and Characterization of Organic Films
Presenter: K.P. Weidkamp, University of Wisconsin-Madison
Authors: K.P. Weidkamp, University of Wisconsin-Madison
L. Fang, University of Wisconsin-Madison
R.J. Hamers, University of Wisconsin-Madison
Correspondent: Click to Email
We have investigated the microstructural, chemical and electronic properties of pentacene thin films formed on Si(001) surfaces. Using FTIR and valence-band photoemission spectroscopy, we find that the initial pentacene molecules deposited onto the surface undergo a transition from sp@super 2@ to sp@super 3@ bonding and partial dissociation, all indicating the formation of covalent C-Si bonds that inhibit diffusion and thereby result in poor pentacene crystal formation. In contrast films prepared by deposition on to Si(001) surfaces that were initially modified with a monolayer of pentacene molecules show no evidence for dissociation and exhibit highly reversible adsorption and desorption, demonstrating that the pentacene molecules do not form covalent bonds with the underlying organic-modified surface. In order to understand how the molecular structure of the interfacial organic layer affects that structure and electronic properties of the pentacene thin films, we have investigated pentacene thin films deposited onto silicon surfaces that were modified with several different organic molecules including cycopentene, dodecene, and phenanthrenequinone. These three molecules are expected to differ significantly in thickness, molecular rigidity, and effective molecular conductivity. AFM images show that the each organic molecular layer induces specific changes in the microstructure of the pentacene films deposited on top. Measurements of the electrical properties through the films will also be presented.