Seeded supersonic beams of oligothiophenes have been developed and used to
grow very high quality films on CaF2 and SiO2. Optical characterizations sh
ow features previously observed only on single crystals and very thin films
. In particular, the vibronic progression of the 0-0 transition is well res
olved at 10 K. Highly supersonic beams give best results. High quality film
s are produced over a range of thicknesses greater than or equal to 500 nm.
The correlation between properties of the films and beam parameters are di
scussed. The energy state of oligomers is envisaged to play a key role in t
he growth. (C) 2000 American Institute of Physics. [S0003-6951(00)01614-4].