Modulating thermoelectric properties in oxygen-passivated Sb2Te3 thin film through grain boundary engineering

TL;DR

This study demonstrates that oxygen passivation of Sb2Te3 thin films enhances thermoelectric performance by modifying grain boundaries, increasing electrical mobility, and reducing thermal conductivity, supported by experimental and theoretical analyses.

Contribution

It introduces a novel approach of oxygen incorporation to engineer grain boundaries and improve thermoelectric properties of Sb2Te3 thin films.

Findings

Oxygen-related impurities wet grain boundaries and create Schottky barriers.

Oxygen chemisorption increases electrical mobility within Sb2Te3.

Spatial thermal conductivity variations confirmed by scanning thermal microscopy.

Abstract

The present study demonstrates the effectiveness of incorporating oxygen atoms into the Sb2Te3 thin film, leading to an improved power factor and reduction in thermal conductivity. Based on the experimental evidence, it can be inferred that oxygen-related impurities preferentially wet the grain boundary (GB) and introduce a double Schottky barrier at the GB interface, promoting energy-dependent carrier scattering, ultimately leading to a rise in the Seebeck coefficient. Additionally, the introduction of chemisorbed oxygen creates a high mobility state within the valence band of Sb2Te3, as corroborated by theoretical calculations, resulting in a significantly increased electrical mobility. These factors collectively contribute to improved thermoelectric performance. A set of Scanning probe (SPM) techniques is used to experimentally confirm the alteration in charge transport resulting from the oxygen-passivated grain boundary. Additionally, Scanning Thermal Microscopy (SThM) is employed to observe the spatial variations of thermal conductivity at the nanoscale regime. This study presents a comprehensive microscopic investigation of the impact of oxygen on the phonon and charge carrier transport characteristics of Sb2Te3 thermoelectric materials and indicates that incorporating oxygen may represent a feasible approach to improve the thermoelectric efficiency of these materials.