Dual-wavelength flash Raman mapping method for measuring thermal diffusivity of suspended 2D nanomaterials

Abstract

This paper presents a “dual-wavelength flash Raman (DFR) mapping method” for in-situ measuring the thermal diffusivity of suspended 2D nanomaterials. Using a periodical heating laser pulse to heat the sample, and using another different wavelength laser pulse as a probe to measure the temperature rises of the sample by its Raman band shifts, the temperature variations of the sample during the heating and cooling period can be determined by changing the time deviation between the heating pulse and the probing pulse. Through changing the position of the probing laser spot, the temperature variation curves at various positions can be measured. The sensitivity and uncertainty analysis shows the measurement accuracy of the mapping method can be significantly improved compared with it of the concentric DFR method. Furthermore, instead of normalization analysis in the DFR method, a specific definition of temperature phase is proposed to analyze the above-mentioned temperature variation curves for characterizing the thermal diffusivity. The uncertainty analysis with a hundred virtual experiments verified that phase analysis is more accurate than the normalization analysis of the same experimental data. When the uncertainty of the temperature measurement is ±2% and each temperature measurement repeated 4 times, with multi-position phase analysis, the uncertainty of the measured thermal diffusivity can be within ±5%.