QUANTITATIVE PHOTOPYROELECTRIC OUT-OF-PHASE SPECTROSCOPY OF AMORPHOUS-SILICON THIN-FILMS DEPOSITED ON CRYSTALLINE SILICON

A photopyroelectric spectrometer with real-time and(or) self-normalization capability was used for both conventional transmission and thermal-wave spectroscopic measurements of amorphous Si thin films, deposited on crystalline Si substrates. Optical-absorption-coefficient spectra were obtained from these measurements and the superior dynamic range of the out-of-phase (quadrature) photopyroelectric signal was established as the preferred measurement method, owing to its zero-background compensation capability. An extension of a photopyroelectric theoretical model was established and successfully tested in the determination of the optical absorption coefficient and the thermal diffusivity of the sample under investigation. Instrumental sensitivity limits of beta-t almost-equal-to 5 x 10(-3) were demonstrated.