Effect of Mn in ZnO Using DFT Calculations: Magnetic and Electronic Changes

GALLEGOS, MARÍA V.; CARLA R. LUNA; LAURA C DAMONTE; JORGE SAMBETH; PAULA JASEN

Roma

Congreso; International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM 2018); 2018

The zinc oxide (ZnO) is classified as a transparent semiconductor, with a wide band gap of 3.4 eV and a large exciton binding energy of 60 eV. The ZnO material crystallizes in the wurtzita structure and is piezoelectric material. This material can be obtained with a variety of techniques such as vapor phase transport, chemical vapor deposition and sputtering. Each technique used involve different growth mechanisms resulting in bulk crystals with defects or/and impurity background, which affect the electrical and optical properties of bulk. Native or intrinsic point defects -such as vacancies, interstitials and antisites- have long been believed to central play an even more important role in ZnO. In the other hand, p-type doping of ZnO has attracted considerable attention due to its potential in several areas as optoelectronic devices. Particularly, Mn-doped ZnO has attracted interest in the last years, in which the Mn is incorporated substitutionally at the Zn site. The present work study the properties of ZnO doped with Mn, and the effect in some chemical and physical properties when charged oxygen vacancy (VOq) are present in the bulk system. For this study is used first-principles calculations based on Density Functional Theory (DFT), implemented in the Vienna Ab initio Simulation Package (VASP) code. Moreover, for improve the results the Hubbard model is taken account for Zn and Mn species.The results shown that the ZnO bulk has non-magnetic behavior; but the substitution of one Zn for one Mn atom leads an increase of magnetic moment from 0.00μB to 4.39 μB per atom. This value is close to the value of 5.0 μB predicted for purely ionic Mn2+ with five unpaired 3d electrons, corresponding to a ferromagnetic state. Regarding to the semiconductor behaviour, the obtained results exhibit that the Mn incorporation still remains the semiconductor nature, there is band gap (Eg) reduction of 70 % respect to ZnO bulk, from 1.76 eV to 0.64 eV. The reduction in Eg arises of the new states that are induce in the forbidden zone due to the Mn d-electrons. These facts do the system Mn-doped ZnO a promising candidate for designing the first ferromagnetic piezoelectric material.