Self-assembled monolayers prepared from ω-thiophene-functionalized n-alkyltrichlorosilane on silicon substrates

Self-assembled monolayers (SAMs) of thienyl-functionalized n-alkyltrichlorosilane (11-(3-thienyl)undecyltrichlorosilane [TUTS]) have been prepared by adsorption from solution and characterized by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle measurements, ellipsometry, and scanning electron microscopy (SEM). Using contact angle and SEM measurements, the film preparation protocol was optimized, resulting in reproducible SAM formation with no adverse deposition of polysiloxane particles. XPS and ellipsometry studies confirmed the existence of SAM formation. AFM results show a smooth and homogeneous SAM, with surface roughness of Ra≤0.2 nm, which is slightly higher than the corresponding values for octadecyltrichlorosilane (OTS) SAMs. Such thiophene-based SAM surfaces can be used for surface-initiated polymerization of thiophene. The resulting formed polythiophene layers at non-compatible surfaces offer some practical applications in manufacturing [W. Plieth, A. Fikus, D. Appelhans, H.-J. Adler, German Patent Application No. 2661977 (1998); D. Appelhans, D. Ferse, H.-J. Adler, A. Fikus, W. Plieth, B. Aldolphi et al., J. Electrochem. Soc. (accepted)].