Characterization of Nanomaterials by Means of Spatially and Frequency Resolved Photothermal Radiometry

Raza Sheikh1,^{1,\star}, Quentin Pompidou2^{2}, Nicolas Horny2^{2}, Heng Ban1^{1}
^{\star} :
1^{1} University of Pittsburgh
2^{2} Université de Reims Champagne-Ardenne
Mots clés : PTR, Photothermal, Radiometry
Résumé :

In this work, we desire to understand the thermal properties of anisotropic bulk and thin films as well as phase change materials (PCM) that are used in the design and fabrication of systems which depend on temperature and heat flux, such as in digital electronic devices. Common methods to measure these properties include non-contact, non-destructive optical techniques. Photothermal radiometry (PTR) is one such technique that uses a modulated laser in the visible spectrum to heat a sheet of a material that can vary in thickness from micrometers to nanometers. The sample produces an infrared response due to the excitation from the laser which is then collected by a detector and analyzed to determine the unknown thermal properties. The work presented in this abstract focuses on progressing a new PTR-based method to measure anisotropic thermal properties, including thermal conductivity measurement in two dimensions (in plane and cross plane). The new system differs from a standard PTR experiment mainly in that the detector translates within a plane to probe different points across the sample so that properties can be measured multidimensionally. Then, an analytical solution for the heat equation can be fitted with the experimentally measured data using the Gauss-Newton method to solve for the unknown quantities. It is expected that these results will agree with standard PTR measurements performed on individual cross sections of the samples representing each material direction. Current challenges include system alignment, system calibration, and programming the heat equation model to be less computationally tedious. The objective of this technique and method is to be able to measure anisotropic properties of materials of interest accurately to enable the use of the next generation of materials in temperature and heat flux sensitive applications. A better understanding of the thermal properties of these materials is crucial in order to be able to properly model thermal systems and optimize designs.

Work In Progress