Raman thermometry analysis: Modelling assumptions revisited

Juliana Jaramillo-Fernandez,Emigdio Chavez-Angel,Clivia M Sotomayor-Torres

doi:10.1016/j.applthermaleng.2017.11.033

Juliana Jaramillo-Fernandez, Emigdio Chavez-Angel + Show 1 more

Open Access

https://doi.org/10.1016/j.applthermaleng.2017.11.033

Copy DOI

Abstract

In Raman thermometry, several assumptions are made to model the heat conduction and to extract the thermal conductivity of the samples from the measured data. In this work, the heat conduction in bulk and mesa-like samples was investigated by numerical simulation and measured by the temperature-induced Raman shift method, to study the range of applicability of these assumptions. The effects of light penetration depth and finite sample size on the accuracy of the thermal conductivity determination were investigated by comparing the results of the finite element method with the usual analytical approximation for bulk samples. We found that the assumptions used in the analytical model can be applied to extract the thermal conductivity in solids if the following conditions are fulfilled: the ratio of light penetration depth to laser spot radius is smaller than 0.5, the ratio of spot radius to sample thickness is smaller than 0.1, and the ratio of spot radius to sample half width is smaller than 0.01.

Highlights

The accurate experimental determination of the thermal conductivity of bulk materials is a very challenging task
We found that the semiinfinite substrate approximation is fulfilled if the half width of the sample is at least 100 times larger than the spot radius, for thermal conductivity predictions with errors below 10% using Eq (2)
We developed a finite-element based numerical simulation of the heating of bulk and microscale mesa-like samples induced by a Gaussian laser beam

Summary

Introduction

The accurate experimental determination of the thermal conductivity of bulk materials is a very challenging task. It usually involves the measurement of temperature differences across a sample in response to the introduction of thermal energy into the system [1,2]. Electrothermal methods generally use microfabricated metal lines to induce Joule heating and probe temperature changes based on the temperature-dependent electrical resistance of the metal strip. Optothermal techniques use laser light as a heat source and measuring probe. The latter approaches are advantageous over electrothermal techniques because they forestall the need for electrical contacts, facilitating measurements in vacuum

Methods

Results

Conclusion