The effect of Cr impurity and Zn vacancy on electronic and magnetic properties of ZnSe crystal

The spin-polarized electronic energy spectra of the ZnCrSe crystal were obtained based on calculations for a supercell containing 64 atoms. First, calculation is performed with an impurity of Cr atom, replacing the Zn atom. In the second variant, the Cr impurity and the vacancy at the Zn atom site are considered simultaneously. The results obtained in the first variant are as follows. It was found that the presence of the Cr atom leads to significant changes in the electronic energy bands, showing a large difference for different spin moments. The density curves of electronic states with opposite spins show an asymmetry, the consequence of which is the existence of a nonzero magnetic moment of the supercell. It was found that in the ZnCrSe crystal electronic 3d states with spin up are present at the Fermi level, i.e. the material is a metal. For spin-down states, the material is a semiconductor in which the Fermi level is inside the band gap. The value of the direct interband gap for electronic states with spin up is equal to 1.56 eV, and the magnetic moment of the supercell is 4.00 . The results obtained by the second variant of the calculation show a significant effect of the vacancy on the zinc site on the electronic structure of the ZnCrSe crystal. The Fermi level now intersects the dispersion curves of the upper part of the valence band for both spin orientations. The magnetic moment of the supercell is 2.74 .

First-principles study of the vacancy defects in ZnIn2Te4 and CdIn2Te4

First-principles calculations were carried out to study the stability and electronic properties of native vacancy defects in the semiconducting ZnIn2Te4 (ZIT) and CdIn2Te4 (CIT). The Zn/Cd and In vacancies are acceptor defects, while the Te vacancy is donor defect. However, the In and Te vacancies dominate in the [Formula: see text]-type and [Formula: see text]-type semiconducting environments, respectively. The Te vacancy is not excited, so it could not compensate the majority of free carriers. The In vacancy prefers to be excited, which generates free hole carriers to compensate the majority of electron carriers. The Zn vacancy is rare in a typical semiconducting environment. Furthermore, all the vacancies induce localized defect states which may be trap centers for the free carriers. Accordingly, these native vacancy defects are destructive for the development of solar cells based on ZIT and CIT, so they should be avoided as much as possible during the growth process.

The study of the behavior of Al impurity in ZnO lattice by a fullerene like model

The fullerene like Zn32Al4O36 clusters were investigated and the oxygen interstitial Oi acceptor intrinsic defect formation energy as well as Al ionization energy were calculated. The effect of lattice packing defects on the electroactivity of Al impurity was investigated. Analysis of the defects formation energies shows the smaller formation energy of interstitial Oi in a comparison with a formation of Zn vacancy. This allows us to formulate recommendations of technological conditions for films deposition, with improved electroactivity of Al donor.

Vacancy ordering induced topological electronic transition in bulk Eu2ZnSb2

Metal-semiconductor transitions from changes in edge chirality from zigzag to armchair were observed in many nanoribbon materials, especially those based on honeycomb lattices. Here, this is generalized to bulk complex Zintl semiconductors, exemplified by Eu2ZnSb2 where the Zn vacancy ordering plays an essential role. Five Eu2ZnSb2 structural models are proposed to guide transmission electron microscopy imaging. Zigzag vacancy ordering models show clear metallicity, while the armchair models are semiconducting with indirect bandgaps that monotonously increase with the relative distances between neighboring ZnSb2 chains. Topological electronic structure changes based on cation ordering in a Zintl compound point toward tunable and possibly switchable topological behavior, since cations in these are often mobile. Thus, their orderings can often be adjusted by temperature, minor alloying, and other approaches. We explain the electronic structure of an interesting thermoelectric and point the way to previously unidentified types of topological electronic transitions in Zintl compounds.

The effect of native vacancy defects on electronic and magnetic properties of ZnO:Mn system

In this paper, the plane wave ultra-soft pseudopotential method was performed to analyze the effect of neutral Zn vacancy (V[Formula: see text]) and O vacancy (V[Formula: see text]) on the electronic and magnetic properties of Mn-doped ZnO systems. In a [Formula: see text] ZnO:Mn supercell, the sites of V[Formula: see text] and V[Formula: see text] were set as nearest neighbor, next nearest neighbor and far nearest neighbor relative to Mn site, respectively. The results indicated that V[Formula: see text] is easier to be produced than V[Formula: see text] in the ZnO:Mn system, and both kinds of defects are more likely to be generated in the nearest neighbor of Mn site. Meanwhile, the ZnO:Mn-V[Formula: see text] system is p-type conductive. The farther the distance between V[Formula: see text] and Mn, the better the conductivity of the system. Contrary to V[Formula: see text], the ZnO:Mn-V[Formula: see text] system is n-type conductive. The farther the distance between V[Formula: see text] and Mn, the worse the conductivity of the system. Furthermore, the ZnO:Mn systems containing neutral V[Formula: see text] or V[Formula: see text] are both likely to be in antiferromagnetic phase. However, the presence of V[Formula: see text] will enhance the possibility, while V[Formula: see text] will weaken it.