The Electronic, Optical, and Thermoelectric Properties of Monolayer PbTe and the Tunability of the Electronic Structure by External Fields and Defects

• Published in: physica status solidi (b) Vol. 257; no. 6
• Main Authors: Bafekry, Asad, Stampfl, Catherine, Peeters, Francois M.
• Format: Journal Article
• Language: English
• Published: 01.06.2020
• Subjects: density functional theory; electronic structure; monolayer PbTe; native defects; strain
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202000182

First‐principles calculations, within the framework of density functional theory, are used to investigate the structural, electronic, optical, and thermoelectric properties of monolayer PbTe. The effect of layer thickness, electric field, strain, and vacancy defects on the electronic and magnetic properties is systematically studied. The results show that the bandgap decreases as the layer thickness increases from monolayer to bulk. With application of an electric field on bilayer PbTe, the bandgap decreases from 70 meV (0.2 V Å−1) to 50 meV (1 V Å−1) when including spin–orbit coupling (SOC). Application of uniaxial strain induces a direct‐to‐indirect bandgap transition for strain greater than +6%. In addition, the bandgap decreases under compressive biaxial strain (with SOC). The effect of vacancy defects on the electronic properties of PbTe is also investigated. Such vacancy defects turn PbTe into a ferromagnetic metal (single vacancy Pb) with a magnetic moment of 1.3 μB, and into an indirect semiconductor with bandgap of 1.2 eV (single Te vacancy) and 1.5 eV (double Pb + Te vacancy). In addition, with change of the Te vacancy concentration, a bandgap of 0.38 eV (5.55%), 0.43 eV (8.33%), and 0.46 eV (11.11%) is predicted. First principles calculations for PbTe monolayers show a wide variation in electronic properties depending on the number of layers, applying an electric field or strain engineering. In addition, vacancy defects can induce magnetism. The possibility to control the band gap and induce magnetism indicate its high potential for use in various technological applications, such as nanoelectronic and spintronic devices.