Far-Infrared Spectroscopic Study of Diamond Films

High quality polycrystalline diamond films grown on Si substrates by microwave plasma enhanced chemical vapor deposition were characterized in a far-infrared spectroscopic study. The spectroscopic transmissivity data were used to derive a model for the complex refractive index (n – ik) as a function of wavelength in the 10 to 200 cm−1 frequency regime. Similar transmissivity and reflectivity data from samples of varying thickness were used to validate this model. The continuum of measured transmissivity and reflectivity data from 10 to 200 cm−1 were shown to be in excellent agreement with the values calculated from the refractive index model. The films were shown to have low loss in this frequency regime.