Ion beam irradiation effect on thermoelectric properties of Bi₂Te₃ and Sb₂Te₃ thin films

Thermoelectric energy harvesting is a very promising application in nuclear power plants for self-maintained wireless sensors. However, the effects of intensive radiation on the performance of thermoelectric materials under relevant reactor environments such as energetic neutrons are not fully understood. In this work, radiation effects of bismuth telluride (Bi₂Te₃) and antimony telluride (Sb₂Te₃) thermoelectric thin film samples prepared by E-beam evaporation are investigated using Ne²⁺ ion irradiations at different fluences of 5 × 10¹⁴, 10¹⁵, 5 × 10¹⁵ and 10¹⁶ ions/cm² with the focus on the transport and structural properties. Electrical conductivities, Seebeck coefficients and power factors are characterized as ion fluence changes. X-ray diffraction (XRD) and transmission electron microscopy (TEM) of the samples are obtained to assess how phase and microstructure influence the transport properties. Carrier concentration and Hall mobility are obtained from Hall effect measurements, which provide further insight into the electrical conductivity and Seebeck coefficient mechanisms. Positive effects of ion irradiations from Ne²⁺ on thermoelectric material property are observed to increase the power factor to 208% for Bi₂Te₃ and 337% for Sb₂Te₃ materials between fluence of 1 and 5 × 10¹⁵ cm², due to the increasing of the electrical conductivity as a result of ionization radiation-enhanced crystallinity. However, under a higher fluence, 5 × 10¹⁵ cm² in this case_, the power factor starts to decrease accordingly, limiting the enhancements of thermoelectric materials properties under intensive radiation environment.