Thermal conductivity of PLD-grown thermoelectric Bi₂Te_2.7Se_0.3 films using temperature-dependent Raman spectroscopy technique

Thermoelectric (TE) materials have increasingly entranced the attention of researchers globally, with a view to providing alternative routes to clean energy. This work reports the first thermal conductivity measurement on pulsed laser deposited Bi₂Se_2.7Te_0.3 (BTS) thin films by a non-contact and optical-based method. Structural characterization revealed well-crystalline films whereas the scanning electron microscope images show abundant grains typical of the BTS nanostructures. A highly stoichiometric composition was observed under energy dispersive spectroscopy. The film's first-order temperature coefficient was estimated by varying the substrate temperature using advanced Raman spectrometer equipped with an inbuilt Linkam stage. The linear dependence of the E_2g phonon mode on temperature and excitation laser power was harnessed to estimate the value of the suspended film's room temperature thermal conductivity. The first-order temperature coefficient was measured to be 0.0359cm⁻¹K⁻¹. The low thermal conductivity measured at room temperature (κ~1.12 Wm⁻¹K⁻¹) is comparable to previously reported values obtained using different conventional techniques. 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 BTS is an excellent material for thermoelectric energy harvesting.