Mobility-Enhanced Thermoelectric Performance in Textured Nanograin Bi₂Se₃, Effect on Scattering and Surface-Like Transport

We report on the effect of artificially generated textures of Bi₂Se₃in thermoelectric performance and low-temperature magnetoresistance [1]. A set of texturized nanograined Bi₂Se₃ samples was investigated, ranging from predominantly <i>c</i>-axis texture to random texture. <i>c</i>-axis oriented layered domains rendered the samples highly conducting due to drastically enhanced mobility, up to 1600 cm²V^-1s^-1 at low temperature, and enhanced both carrier concentration and electrical conductivity. The largest power factor of 800 µWm^-1K^-2 and highest 0.14 both at 300K were observed in a sample with a predominantly layered and c-axis oriented texture. The carrier scattering mechanism in the samples changed from mostly electron-phonon interaction at in the predominantly layered microstructure, to disorder-related scattering as the texture became random. The weak antilocalization effect was observed predominantly in the random textured samples, pointing towards enhanced surface-like transport channels. The phase coherence length evaluated using the Hikami-Larkin-Nagaoka model resulted in a high value of roughly 600 nm regardless of the texture. In the <i>c</i>-axis oriented layered Bi₂Se₃ oxidic insulating inclusions from either Fe₃O₄ or SiO₂ were incorporated. Both insulating phases reduced mobility. However, finely dispersed Fe₃O₄ secondary phase in Bi₂Se₃ resulted in a further increase of 0.2 due to much increased electrical conductivity. The combined effect of layered texture and Fe₃O₄ secondary phase resulted in an overall increase of around 50% compared to a non-textured polycrystal.<br/><br/>[1] Samaneh Bayesteh <i>et al.</i>, Mat. Today Physics <b>24</b> (2022) 100669,<br/>DOI: 10.1016/j.mtphys.2022.100669.