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D. Dietzel, S. Chotikaprakhan, H. Bangert, C. Eisenmenger-Sittner:
"Thermoreflectance microscopy of Cu coatings on Carbon";
Poster: EUROMAT 2003, Lausanne/Schweiz; 01.09.2003 - 04.09.2003.

In composite systems consisting of copper coatings on glassy carbon e.g. applied in thermal management problems, the relevant heat transport parameters are the effective thermal properties of the copper coating which can vary considerably with the plasma deposition conditions. By conventional techniques it is difficult or nearly impossible to measure the effective thermal properties of the copper coatings with a coating thickness in the submicron and micron range and to distinguish them from the effect of the thermal contact resistance between the copper coating and the carbon substrate. To overcome this experimental problem in this work, an alternative thermal wave method is introduced which relies on the spatial separation of the excitation and detection of the thermoreflectance signal: By controlled lateral defocusing between the modulated pump laser beam and the continuous probe laser beam, with the beam diameters in the micron range, the distance bridged by the measured thermal wave can be varied and the lateral heat transport along the coating becomes accessible to measurement. Additionally, lateral inhomogeneities of the coating and local defects of contact between coating and substrate are visualized by this method. In order to optimize the measurements, e.g. with respect to the appropriate interval of heating modulation frequencies and selection of the size of the heating and detection spots, and to verify the reliability of the quantitative interpretation with respect to the thermal parameters, the measurable signals have been simulated numerically by considering one-dimensional and three-dimensional heat transport inside the samples.