Thermoreflectance temperature measurement with millimeter wave

Abstract

GigaHertz (GHz) thermoreflectance technique is developed to measure the transient temperature of metal and semiconductor materials located behind an opaque surface. The principle is based on the synchronous detection, using a commercial THz pyrometer, of a modulated millimeter wave (at 110 GHz) reflected by the sample hidden behind a shield layer. Measurements were performed on aluminum, copper, and silicon bulks hidden by a 5 cm thick Teflon plate. We report the first measurement of the thermoreflectance coefficient which exhibits a value 100 times higher at 2.8 mm radiation than those measured at visible wavelengths for both metallic and semiconductor materials. This giant thermoreflectance coefficient κ, close to 10(-3) K(-1) versus 10(-5) K(-1) for the visible domain, is very promising for future thermoreflectance applications.

Analysis of the Thermo-Reflectivity Coefficient Influence Using Photothermal Pump–Probe Techniques

“…[1][2][3][4][5][6][7][8] In this study, we present an analytical thermo-reflectivity coefficient depending on the thermo-optical properties of the sample and surrounding fluid. This coefficient is related to the thermoreflectance coefficient measured in several experimental works, [13][14][15] leading us to believe that it must influence both TL and TM experiments. We analyze the role of this effect in two semi-transparent materials for TL and TM theoretical signals, considering continuous-wave (cw) and pulsed laser excitations.…”

Capability of THz for Thermo-transmittance/water content measurements of insulating materials: heat and mass transfer

“…The infrared imaging technique showed to be efficient to evaluate the heat transport properties in chemical reaction at micro scale [2]. When the sample is opaque in visible or infrared range, THz could be an efficient alternative tool for non-contact temperature imaging [3]. Therefore the 2D and 3D temperature distribution could be reconstructed by tomography [4].…”

“…THz waves have been rarely applied as a tool for temperature measurement [3]. C. Pradere et al used THz source with infrared mono-detector to estimate the thermal reflectance coefficient for metal and semiconductor materials.…”

Multispectral IR thermotransmittance technique for temperature measurement

“…THz w aves are defined as a very far IR w avelength covering a spectral range from 30 µm to 3 mm. Based on w orks previously reported [4], the thermoreflectance technique from visible to THz w avelengths has been extended. Thus, the ability of those millimetric radiations to pass through a thick plate of Teflon opaque to visible w avelengths and perform transient temperature measurements of metallic and semiconductor materials has been demonstrated.…”