Ferromagnetism in ZnO with(Mn,Li) codoping

First-principles calculations were performed to investigate the magnetic properties of Zn（Mn,Li）O based on the Perdew-Burke-Ernzerhof form of the generalized gradient approximation.Antiferromagnetic（AFM） ordering is the ground state in Mn-doped ZnO system without the codopant of Li,while seven different geometrical configurations of Zn（Mn,Li）O prefer stable ferromagnetic（FM） ordering.We found that dopant Li can effectively change the magnetic coupling in the ZnMnO system.The Curie temperature（TC） of FM ordering depends on the geometric configuration,and the highest T C is about 1388 K.The FM stabilization is greatly affected by Mn-Mn distance rather than by the position of dopant Li.We propose that dopant Li mediates FM coupling through a double exchange interaction or an RKKY interaction when Li is located,respectively,near or far from Mn ions.

Electronic Structure and Optical Properties of Antimony-Doped SnO_2 from First-Principle Study

A first-principles study has been performed to calculate the electronic and optical properties of the SbxSn1xO system.The simulations are based upon the method of generalized gradient approximations with the Perdew-Burke-Ernzerhof form in the framework of density functional theory.The supercell structure shows a trend from expanding to shrinking with the increasing Sb concentration.The increasing Sb concentration induces the band gap narrowing.Optical transition has shifted to the low energy range with increasing Sb concentration.Other important optical constants such as the dielectric function,reflectivity,refractive index,and electron energy loss function for Sb-doped SnO2 are discussed.The optical absorption edge of SnO2 doped with Sb also shows a redshift.

The electronic and magnetic properties of (Mn,C)-codoped ZnO diluted magnetic semiconductor

The electronic and magnetic properties of （Mn,C）-codoped ZnO are studied in the Perdew Burke-Ernzerhof form of generalized gradient approximation of the density functional theory. By investigating five geometrical configurations, we find that Mn doped ZnO exhibits anti-ferromagnetic or spin-glass behaviour, and there are no carriers to mediate the long range ferromagnetic （FM） interaction without acceptor co-doping. We observe that the FM interaction for （Mn,C）-codoped ZnO is due to the hybridization between C 2p and Mn 3d states, which is strong enough to lead to hole-mediated ferromagnetism at room temperature. Meanwhile, we demonstrate that ZnO co-doped with Mn and C has a stable FM ground state and show that the （Mn,C）-codoped ZnO is FM semiconductor with super-high Curie temperature （Tc =5475 K）. These results are conducive to the design of dilute magnetic semiconductors with codopants for spintronics applications.

First-Principles Study of Ag-Doped GaAs Nanowires

The structural and electronic properties of undoped and Ag-doped unpassivated wurtzite GaAs nanowires(NWs),as well as their stability,are investigated within the first-principles frame.The calculated formation energies show that the single Ag energetically prefers to substitute the surface Ga(E_(f)=-0.529 eV)under As-rich conditions,and creates a much shallower(0.19 eV above the Fermi)acceptor level,which is of typical p-type character.With the increase in the Ag concentration,the p-type behavior gradually weakens and the n-type character arises.Thus,one can expect to synthesize Ag-doped GaAs NWs for p-type or n-type applications by controlling their Ag concentration and microarrangement.