  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.
