A DFT Investigation on Structural and Electronic Properties of Pure and Sr-Doped Wurtzite ZnO

Abstract

The aim of this study was to investigate structural and electronic properties of pure and Strontium-doped wurtzite ZnO using first principles density functional calculations (DFT). The first principle calculation is a computational method to study the electronic structure of materials. The self-consistent calculation was done using Generalized Gradient Approximation (GGA) with BLYP functional implemented on Quantum ESPRESSO package to generate the band structure and density of states of the materials taken under consideration. The Strontium doping caused the increase in lattice volume and slight distortions at the unit cell parameters in a wurtzite structure. This doping process increased the band-gap energy (E g ) at low percentage 25% (E g = 1.55eV) and 50% (E g = 2.33eV) with indirect band-gap and direct band gap at high percentages 75% (E g = 2.38eV) and 100% (E g = 3.368eV), which we call it wide direct band gap. The lattice parameters obtained at the level of GGA–BLYP approach was found to be (a = b = 3.412A o , and c = 5.205A o ) in good agreement with either previously reported theoretical or experimental work. The calculated band-gap of the pure wurtzite ZnO is found to be 0.935eV. This is a new result because in our knowledge nobody has been work in wurtzite ZnO used the exchange correlation BLYP functional based on DFT. Compared with experimental value (3.37eV), the calculated band-gap was much smaller because of the well-known conduction band, but the result did not affect the accuracy of the comparison of the related properties of the crystals. The results obtained can be used as a basis for more in depth calculations, which may include calculating the optical properties with additional dopant that can be used on optical and photo-catalytic applications.