Oxygen adsorption effects on geometries and electronics of thermoelectric PbTe surfaces

Abstract

Surface oxidation on PbTe during the synthesis and operation inevitably degrades its thermoelectric performance. We theoretically investigate oxygen adsorption on six stable PbTe surfaces. The oxygen adsorption on PbTe surfaces leads to a significantly strong adsorption energy (−3.06 eV/O) at the (1 1 1) surface, and a ∼30 % expansion of the first interlayer spacing at the stepped surfaces. These facilitate the oxygen penetration and initiates the surface oxidation. From electronic structure analysis, oxygen adsorptions induce PbTe thermoelectric performance degradation due to density of states reduction at the Fermi level, defect levels within the bandgap, and carrier-type inversion. Thus, we propose the PbTe anti-oxidation strategies including eliminating surface defects, passivating active oxygen adsorption sites, and applying anti-oxidation coatings.