Effects of Oxygen Adsorption and Temperature on Lead Telluride Surfaces

Abstract

As a traditional thermoelectric material, PbTe exhibits a high peak zT value. However, it is highly susceptible to oxidation during either synthesis or device operation. Thus, it is essential to understand the oxidation behavior at finite temperatures and its effects on the geometries of PbTe surfaces. Focusing on oxygen adsorption at two stable PbTe(100) and PbTe(111) surfaces, using cluster expansion, we identify the most stable adsorption configurations of 0.5O−PbTe(100) and 0.33O−PbTe(111) with oxygen coverages of 0.5 and 0.33, respectively. Electronic structure calculations reveal that oxygen atoms form covalent bonds with surface Te atoms. Ab initio molecular dynamics investigations demonstrate temperature is a critical factor that damages PbTe surfaces and drives oxygen atoms into sublayers, forming surface oxides. Oxygen atoms migrate into a deeper sublayer on PbTe(111) than on PbTe(100). Increasing temperature and oxygen coverage aggravate these effects. Surface oxidation fundamentally deteriorates electrical transport characteristics by changing carrier concentration, inducing transitions between n- and p-type conduction, and decreasing carrier mobility. This ultimately leads to significant degradation in its thermoelectric performance. Possible approaches include depositing dense passivation layers to block oxygen adsorption and diffusion.