Photothermal Characterization of Surfaces and Interfaces

Abstract

Photothermal (PT) generation, referring to the heating of a sample and its surroundings by electromagnetic irradiation, can produce many effects, including refractive-index gradients, acoustic emission, surface deformation, reflectivity changes, desorption, phase change, ablation, and “gray-body” infrared emission, providing various techniques for materials characterization. Many methods of detecting these PT effects are possible, using “probe” laser beams, transducers, microphones, pyrometers, or infrared detectors. Several PT effects often occur simultaneously, depending on whether there is mainly surface heating (opaque sample) or mainly bulk heating (transparent sample), and on the nature of the coupling medium, if any. The choice of a suitable PT effect and the appropriate detection scheme depend on the nature of the sample and its environment, the light source used, and the measurement desired. This chapter describes the experimental arrangements and detection schemes for PT surface heating applied to surface and interface characterizations, and provides recent examples of such studies utilizing pulsed photoacoustic detection for imaging of layered structures and for detecting laser ablation, photothermal refraction of a probe beam to monitor pulsed PT desorption from a surface, and photothermal radiometry following pulsed heating of a layered structure for measuring the subsurface thermal contact resistance.KeywordsProbe BeamThermal Contact ResistanceRefractive Index GradientPhotothermal RefractionThin Layered StructureThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.