Ultrathin nanowire PdX2 (X = P, As): stability, electronic transport and thermoelectric properties

Abstract

In the last few decades, the miniaturization of devices has been taking place and therefore the quest for new nanowires has become more significant. In the present study, we have investigated the geometry of new ultrathin nanowires (NWs) of PdP₂ and PdAs₂ that could be obtained experimentally. We have optimized the pentagonal structures of both the NWs and studied their dynamical stability using the phonon dispersion curve. The electronic band structure shows semiconducting behaviour of PdP₂ NWs with a band gap of 380 meV and PdAs₂ NWs with a band gap of 294 meV, with higher charge carrier mobility than that of their 2D counterparts. The NWs show a band gap of 840 meV and 740 meV for PdP₂ and PdAs₂, respectively, through hybrid potential calculations. The PdX₂ structure shows a transition from semiconducting to semi-metallic behaviour at a compressive strain of 8% within a sustainable pressure of 0.2–0.3 GPa. A negative differential conductance (NDC) effect is observed in the current–voltage graph for both the NWs. The semi-metallic behaviour with an asymmetric density of states near the Fermi energy boosts the Seebeck co-efficient value and therefore the ZT_e value is enhanced for both the nanowires. The strained PdP₂ and PdAs₂ NWs show ZT_e values of 4.75 and 5.49, respectively. Our study stimulates the feasibility of both nanowires and thermoelectric applications for the conversion of waste heat into electricity.