Study of a new layered ternary chalcogenide CuZnTe2 and its potassium intercalation effect

Abstract

A new layered ternary chalcogenide CuZnTe _2 and its effect due to potassium (K) intercalation have been investigated using ab-initio method under the framework of density functional theory (DFT). Here, we report the structural, electronic and elastic properties of both proposed parent compound CuZnTe _2 and intercalated KCuZnTe _2 . The electronic band structures and the density of states (DOS) of both these chalcogenides have also been studied. The parent compound demonstrates p -type conductivity with the energy band gap of 0.7 eV but surprisingly, the increase of energy gap (1.5 eV) is found in the intercalated KCuZnTe _2 , a direct-transition type semiconductor. The optical absorption result in KCuZnTe _2 also shows the identical value of gap energy calculated by Wood-Tauc theory. The density of states (DOS) in the valence band for both compounds is dominated by the partial contribution of Cu/Zn 3 d and Te 5 p orbitals but the prime contribution of Cu/Zn 4 s and Te 5 s mainly in the conduction band DOS. The DOS value at around Fermi level in these chalcogenides is indicating the degeneracy behavior of a semiconductor. Both compounds are mechanically stable and also malleable. We also calculated the thermal properties in the intercalated KCuZnTe _2 using quasi-harmonic Debye model. The observed values of Debye temperature, specific heat capacities and volume expansion coefficient using this model is almost consistent with the estimated values given in theory.

Keywords

• first-principles study
• chemical intercalation
• electronic band structures
• optical absorption
• elastic constants
• specific heats