Enhanced figure of merit in two-dimensional ZrNiSn nanosheets for thermoelectric applications

Abstract

A novel 2D Half Heusler ZrNiSn nanosheet for thermoelectric applications is is designed from the bulk half Heusler ZrNiSn through the first principle calculation. Investigation of bulk half Heusler and 2D ZrNiSn nanosheet has been performed through Quantum Espresso code based on Density Functional Theory-plane wave basis set. Electronic band structure and density of states calculations were used to study the confinement effects. On moving from bulk to 2D due to confinement, change of structure is observed from face centered cubic to trigonal. Semiconducting nature of bulk ZrNiSn is undisturbed while moving to 2D nanosheet, however band gap is widened from 0.46 to 1.3 eV due to the restricted motion of electron in one direction. Compared to bulk ZrNiSn, 2D nanosheet was found to have high Seebeck coefficient, low thermal conductivity and high ZT which makes 2D ZrNiSn nanosheet suitable for thermoelectric applications. Two dimensional structures with atomically thin nature and flat surface have the potential to form van der Waals hetero junctions paving the way for device fabrication at nanoscale level.