Local phonon mode in thermoelectric Bi2Te2Se from charge neutral antisites

TL;DR

This study identifies a charge-neutral antisite defect-induced local phonon mode in Bi2Te2Se, revealing its temperature behavior and impact on thermal transport, which is crucial for thermoelectric performance.

Contribution

It provides the first direct identification of a charge-neutral antisite defect local mode in Bi2Te2Se using temperature-dependent Raman spectroscopy.

Findings

Identified a specific local phonon mode linked to antisite defects.

Observed temperature-independent broadening of the mode.

Mode behavior explained by anharmonic Klemens's model.

Abstract

Local modes caused by defects play a significant role in the thermal transport properties of thermoelectrics. Of particular interest are charge-neutral defects that suppress thermal conductivity, without significantly reducing electrical transport. Here we report a temperature dependent Raman study, that identifies such a mode in a standard thermoelectric material, Bi2Te2Se. One of the modes observed, whose origin has been debated for decades, was shown mostly likely to be an antisite defect induced local mode. The anomalous temperature independent broadening of the local mode is ascribed to the random arrangement of Se atoms. The temperature renormalization of all modes are well explained by an anharmonic model-Klemens's model.