Surface-enhanced Raman spectroscopy technique for the estimation of thermal conductivity of thin film thermoelectric materials

Thermoelectric (TE) materials are remarkable semiconductors employed for heat-electricity interconversion. The performance of TE materials is assessed based on the dimensionless figure of merit (ZT). The figure of merit depends on the electrical conductivity, thermal conductivity, temperature, and Seebeck coefficient. The measurement for electrical properties is somewhat straightforward. However, the thermal conductivity measurement is incredibly challenging especially for thin film TEs, which find variety of applications in health and electronics sectors. Conventionally, the thermal conductivity is measured using methods such as 3-omega technique, which requires a series of sample preparation work. In this work, a novel thermal conductivity measurement technique based on the temperature response of the Raman vibrational modes of the materials is established. The films’ first-order temperature coefficient was estimated by varying the substrate temperature using advanced Raman spectrometer equipped with inbuilt Linkam stage. The linear dependence of the E2g phonon mode on temperature and excitation laser power was harnessed to estimate the value of the suspended film’s room temperature thermal conductivity. This work proved the potential of Raman spectroscopy to estimate the thermal conductivity as an excellent alternative tool to the existing expensive and laborious techniques. In addition, this work demonstrated that bismuth telluride selenide is an excellent material for TE energy harvesting.