Infrared dielectric function and vibrational modes of pentacene thin films

Generalized infrared spectroscopic ellipsometry over the wave-number range from 300 to 2000 cm−1 is used for precise determination of the dielectric function, frequency, amplitude, and broadening parameters of 27 infrared active modes for polarization parallel to the growth surface of pentacene thin films obtained by molecular-beam deposition on glass. No in-plane anisotropy was detected, which is indicative for a random orientation of crystallites around the growth direction supporting previous x-ray diffraction results.