Temperature and Strain Effects in Micro-Raman Thermometry for Measuring In-Plane Thermal Conductivity of Thin Films

Micro-Raman thermometry is an effective method for measuring thermal conductivity of thin films. It features noncontact and nondestructive probing and convenience of sample preparation. However, there is a concern of its accuracy when using the Raman peak shift as the temperature transducer since it responds to both temperature and strain upon optical heating. In this work, a series of detailed experiments are carried out to evaluate contributions to Raman signals from temperature only vs. from thermomechanical strain. It is shown that using proper calibration, contributions to Raman signals from temperature only and from thermomechanical strain can be decoupled and thermal conductivity can be evaluated correctly. These procedures are then applied to bismuth telluride thin films to illustrate measurement of thin film thermal conductivity.