Fermi energy-level shift of p-type AgBiSe2 single crystal featuring semiconductor-to-metal transition at cryogenics

Abstract

A ternary chalcogenide AgBiSe2 (ABS) crystal was grown using the Bridgman–Stockbarger technique followed by XRD and Raman shift analysis to verify the structural properties of the ABS crystal. The temperature (300–4.2 K)-dependent resistivity (ρ) shows semiconductor behavior down to 109 K and transforms to metallic behavior down to 19 K. Due to the localization behavior, the resistance shows an upturn up on further decrease in temperature. Charge defects caused by atomic vacancies as well as anti-site defects are thermodynamically induced, and have the potential to shift the Fermi energy level. The two transitions at 109 and 19 K in ρ(T) demonstrate consequent changes as a semiconductor-to-metal transition. The magnetoresistance MR graph exhibits resistive behavior with respect to the magnetic field applied and displays a ‘U’ shape at 300 K, which changes to a ‘V’ shape at 4.2 K. The Hall effect measurements reveal that the majority carrier is a hole. The carrier density as well as mobility changes with respect to temperature are analyzed within the preview of the Ioffe–Regel criterion. ABS is a promising p-type candidate with efficient characteristics that needs further elaboration for thermoelectric, photonic and photovoltaic applications.