(165a) Covalent Molecular Assembly of Conducting Polymers on Silicon

Organic functionalization of semiconducting surfaces is emerging as an important area in the development of new semiconductor based materials and devices. Polythiophenes are one of the most important classes of conjugated polymers with a wide range of electronic properties and applications as conducting films, electrochromics, chemical sensing, memory, light emitting devices and field effect transistors. By self assembling the polythiophene film on silicon interfaces, these characteristic properties of polythiophenes can be incorporated into silicon-based electronic devices.

In this work, we report formation of nano-structured, regio-regular conducting polythiophene films by covalently binding the thiophene to silicon. The covalently bound nanostructured films possessed uniformity, good thermal and chemical stabilities. Mobility and conductivity characterizations carried out showed increase in conductivity with doping.

We further investigated the deposition of multilayers of covalently bonded polythiophene films on silicon substrates using an intermediate linker as well as by modifying the functional end group of the polythiophene. The electronic properties of the polythiophene films can be significantly improved by multilayer assemblies. The covalent bonding of polythiophene was confirmed using the spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), Fourier transform - infrared spectroscopy (FTIR), and UV-Vis spectroscopy.

By covalent bonding with the substrate, conducting polymers can be incorporated as constituents micro- and nano scale devices such as chemical sensors and Field effect transistors.