Band engineering of monolayer CaI2, a first-principles approach

Abstract

ABSTRACT Motivated by recent proposal of enhancing performance of materials via band engineering, first principles calculations are performed to investigate the changes in band structure of monolayer CaI2 by applying isotropic biaxial strain. CaI2 monolayer is found to be an indirect band-gap semiconductor with band-gap of 3.77 eV. Phonon dispersion includes only real phonon modes which reveals dynamical stability of the material. Calculations show that there is a decrease in band-gap as well as effective mass of carriers of the material with increase in compressive strain. At strains of −4%, −8% and −12%, the band gap is found to be 3.49 eV, 3.14 eV and 2.74 eV, respectively. Both the maxima of valence band and minima of conduction band move downwards and maxima of conduction band shifts from high symmetry point M to point K. The changes in band structure and density of states are in consistence with one another. The effective mass of carriers also decreases resulting in an increase in mobility. With a final band-gap of 2.74 eV and increased mobility at −12% strain, the material can be used for different applications as a wide band-gap semiconducting material.