Thermodynamics and robust n-type charge carrier density in Co-doped FeTe2: strain strategy

Abstract

Herein, we investigated the combined effect of Co-doping and strain (biaxial [110] and hydrostatic [111]) on the thermodynamics and electronic structure of the FeTe2 motif using ab-initio calculations by considering the strong correlation effects. The pristine one has a non-magnetic semiconducting nature with an indirect band gap (E g ) of 0.384 eV. Interestingly, our results revealed that the Co-doping at the Fe site induced an n-type conductivity (i.e. few states are crossing the Fermi level from the valence to conduction band) in the system having a substantial charge carrier density magnitude of 0.14 × 1021 cm−3. The metallicity mainly comprises the Co-3d orbitals along with a significant contribution from Fe-3d states. Thermodynamic, mechanical, and dynamical stability of the Co-doped FeTe2 structure is confirmed by computing the formation energetic, elastic constants, and phonon band structure, respectively. Generally, an increasing and decreasing trend in E g value is evident against the applied compressive and tensile strains having ranged from −5% to +5% for the case of the undoped system, respectively. On the other hand, the Co-doped structure maintained its n-type conduction against considered both types of strains. Moreover, it is demonstrated that compressive strains strengthen the charge carrier density amplitude, while tensile strains show a negative impact. Hence, the present work displays that robust n-type conductivity and stable structure of Co-doped FeTe2 system, makes it a desirable candidate for device applications.