Oxygen-substituted tetrathiafulvalene (TTF) derivatives of bis(ethlenedioxy)tetrathiafulvalene (BEDO-TTF) were deposited on -COOH-terminated alkylsilane self-assembled monolayers (SAMs). The BEDO-TTF molecules were effectively attached on the -COOH-terminated SAMs. A formation of mixed valence state (MVS), which is a characteristic conducting phase of TTF, was observed by Fourier transform infrared spectroscopy. Such MVS formation is estimated to be brought about by an appearance of charge-transfer complex of (BEDO-TTF)(2)((COOHOOC)-H-...-O-...) through a chemical reaction with -COOH group of the surface. Atomic force microscopy images revealed the existence of many small islands on the surface. It is expected that the first layer of BEDO-TTF molecules are absorbed onto -COOH group of the surface through the reaction, then the first layer stimulates a crystallization of BEDO-TTF above it, giving rise to the islands formation. (c) 2004 Elsevier B.V. All rights reserved.