The Structure of -sexithiophene ultra-thin films on passivated Si(001) surfaces

Hiraga, Kenta*; Toyoshima, Hiroaki*; Ono, Shinya*; Hirao, Norie; Sekiguchi, Tetsuhiro  ; Shimoyama, Iwao   ; Baba, Yuji  ; Mukai, Kozo*; Yoshinobu, Jun*; Tanaka, Masatoshi*

It is important to control orientation structure and electric property at the interface between organic semiconductor molecule and surfaces of semiconductor substrates in order for the development of commercial base organic transistors and solar cells. In the present work, we have investigated the surface reflection spectroscopy (RDS, SRDS), S-1s angle resolved near-edge X-ray absorption fine-structure (NEXAFS), and UPS for -sexithiophene (-6T) ultra-thin films with a variety of thickness from 0.25 to 1.0 nm. The results of RDS and SDRS, and NEXAFS gave the information on orientation structure of the -6T molecules. In contrast, UPS gave the uniformity of the thin films. We report on how orientation structures and condensed structures are changed depending on the method of passivation and the film thickness.