Molecular beam deposition of thin films of organic semiconductors.

The ultra-high vacuum technique of organic molecular beam deposition (OMBD) has been recently proved to provide a very good method for growing highly controlled thin films of organic semiconductors. The approximate ordering of a crystalline layer to a substrate, also called quasi-epitaxy, can be achieved with a proper choice of substrate and deposition conditions. Poly- and oligo-thiophenes are among the most interesting and widely studied organic semiconductors for applications in electronic and photonic devices, thanks to their high carrier mobility and large nonlinear optical response, combined with an exceptionally high flexibility of molecular engineering. Here, the deposition and the main properties of films of substituted sexithiophene molecules (6T) obtained by OMBD are discussed on the basis of X-ray diffraction and optical absorption measurements.