PHOTOTHERMAL CHARACTERIZATION OF VERTICAL AND SLANTED THERMAL BARRIERS - A QUANTITATIVE COMPARISON OF MIRAGE, THERMOREFLECTANCE, AND INFRARED RADIOMETRY

We present a quantitative and comparative study of three different pho tothermal techniques based on the signal produced on vertical/slanted thermal barriers under a variety of barrier/sample conditions. Models based on integral methods are developed to calculate the amplitude and phase of the sample surface temperature and mirage deflection in surr ounding air. The geometries studied include: vertical, tilted, buried, and finite size barriers separating identical or different media, The models incorporate the probe and pump beam sizes, the thermal resista nce of the barrier and the optothermal characteristics of the sample. Experimental measurements are performed on a variety of fabricated bar riers with three modulated photothermal techniques: the thermoreflecta nce, infrared radiometry, and mirage detection. We discuss in a compar ative way the limits, drawbacks and the applicability of each techniqu e. Model fits to the experimental results allow characterization of th e thermal barrier (spatial localization, geometry, orientation, and si ze) and provide an accurate determination of its thermal resistance. ( C) 1996 American Institute of Physics.