Effect of Mn in ZnO using DFT Calculations: Magnetic and electronic changes

M.V.GALLEGOS; C.ROMINA LUNA; L.C. DAMONTE; J.SAMBETH; P.C.RIVAS

Simposio; 25th International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM 2018); 2018

The zinc oxide (ZnO) is classified as a transparent semiconductor, with a wideband gap of 3.4 eV and a large exciton binding energy of 60 eV. The ZnO materialwhich crystallizes in the wurtzita structure is piezoelectric material. This materialcan be obtained with a variety of techniques such as vapor phase transport,chemical vapor deposition and sputtering. Each technique used involve differentgrowth mechanisms resulting in bulk crystals with defects or/and impurity background,which affect the electrical and optical properties of bulk. Native or intrinsicpoint defects -such as vacancies, interstitials and antisites- have long been believedto play a central and even more important role in ZnO. In the other hand,p-type doping of ZnO has attracted considerable attention due to its potential inseveral areas as optoelectronic devices. Particularly, Mn-doped ZnO has attractedinterest in the last years since Mn is incorporated substitutionally at the Zn site.The present work studies the properties of Mn-doped ZnO, and the effect in somechemical and physical properties when charged oxygen vacancy (VOq) are presentin the bulk system. First-principles calculations based on Density Functional Theory(DFT), implemented in the Vienna Ab initio Simulation Package (VASP) code isused. Moreover, for improve the results for Zn and Mn species the Hubbard modelis taken account.The results shown that the ZnO bulk has non-magnetic behavior; but the substitutionof one Zn for one Mn atom leads to an increase of magnetic moment from0.00 μB to 4.39 μB per atom. This value is close to the value of 5.0 μB predicted forpurely ionic Mn2+ with five unpaired 3d electrons, corresponding to a ferromagneticstate. Regarding to the semiconductor behaviour, the obtained results exhibitthat the semiconductor nature still remains with Mn incorporation, leading to aband gap (Eg) reduction of 70 % respect to ZnO bulk, from 1.76 eV to 0.64 eV. Thereduction in Eg arises from the new states that are induced in the forbidden zonedue to the Mn d-electrons. These facts do the system Mn-doped ZnO a promisingcandidate for designing the first ferromagnetic piezoelectric material.