Parametric study of the frequency-domain thermoreflectance technique

Abstract

Thermal conductivity measurements of non-metals via combined time-and frequency-domain thermoreflectance without a metal film transducer Review of Scientific Instruments 87, 094902 (2016) Without requiring regression for parameter determination, one-dimensional (1D) analytical models are used by many research groups to extract the thermal properties in frequency-domain thermoreflectance measurements. Experimentally, this approach involves heating the sample with a pump laser and probing the temperature response with spatially coincident probe laser. Micron order lateral resolution can be obtained by tightly focusing the pump and probe lasers. However, small laser beam spot sizes necessarily bring into question the assumptions associated with 1D analytical models. In this study, we analyzed the applicability of 1D analytical models by comparing to 2D analytical and fully numerical models. Specifically, we considered a generic nlayer two-dimensional (2D), axisymmetric analytical model including effects of volumetric heat absorption, contact resistance, and anisotropic properties. In addition, a finite element numerical model was employed to consider nonlinear effects caused by temperature dependent thermal conductivity. Nonlinearity is of germane importance to frequency domain approaches because the experimental geometry is such that the probe is always sensing the maximum temperature fluctuation. To quantify the applicability of the 1D model, parametric studies were performed considering the effects of: film thickness, heating laser size, probe laser size, substrate-to-film effusivity ratio, interfacial thermal resistance between layers, volumetric heating, substrate thermal conductivity, nonlinear boundary conditions, and anisotropic and temperature dependent thermal conductivity. V C 2012 American Institute of Physics. [http://dx

Local measurement of bulk thermal diffusivity using photothermal radiometry

“…Consequently, the film and the layer are not expected to significantly influence the temperature profile for materials having moderate-to-large values of diffusivity. 23,31,32 Reference samples consisted of disks with diameters of 12-25 mm and thicknesses in the range of 1-2 mm. In addition to the reference standards, POCO ® graphite [laser flash analysis (LFA)-reference sample from NETZSCH, sample ID AXM-5Q] was selected to gauge the ability to accurately extract the value of D corresponding to bulk properties for materials having large-scale structure (100 nm to 10 μm).…”

The study of frequency-scan photothermal reflectance technique for thermal diffusivity measurement

“…The theoretical models with multi-layered structures have been developed by Reichling and Gronbeck, 5 Lepoutre et al, 6 Li and Zhang 7 and Xing et al 8 In those works, the influences of important experimental factors and various measurement strategies were discussed. Based on these theoretical models, a number of lab-oriented experiments were developed to extract thermal properties, [9][10][11][12][13] measure interface thermal resistance, [14][15][16] and detect invisible defects underneath the sample surface.…”