Thermal difference spectroscopy

Abstract

We have developed a simple method of collecting the thermal derivative spectra of solids. In this method, a sample’s reflectance is measured at two specific temperatures and the thermal difference of the material’s reflectance is calculated. By digitally averaging these differences, we obtain spectra equivalent to thermal modulation spectra. Since this is not a modulation technique we have named it thermal difference spectroscopy. Using the thermal difference spectrometer we have achieved a base line noise level in the normalized thermal difference reflectance spectrum (ΔR/R) of approximately 5×10−5. To demonstrate the technique’s utility as a truly noncontact derivative spectroscopy we have collected thermal difference spectra of both thin-film and bulk samples.