Electronic Structure of Zinc-Blende Zn_0.5Co_0.5Se: Theoretical Study

Abstract

In this paper we present partial densities of states for spin-polarized antiferromagnetic phase of Zn0.5 Co0.5 Se as well as schematic layouts of the bands, obtained using the ab initio self-consistent semi-relativistic linear muffin tin orbital method. We also present, from theoretical point of view, the analysis of influence of the transition metal cobalt on the electronic structure of a pure ZnSe.

The influence of transition metals on the electronic structure of ZnSe host crystal: fundamental reflectivity analysis

“…The energy positions of the non-hybridized e 2 spin-up states for Fe 2+ are also almost equal to values obtained for Mn 2+ in zinc sulphides, selenides, and tellurides [10,11,47]. This behaviour of the e 2 states of Mn 2+ and Fe 2+ is also confirmed by calculations [44,48].…”

“…The mean energy position of five spin-up electrons, which are immersed and partially hybridized in the valence band of the ZnSe host crystal, is situated about 3.5 eV below the VBM [9]. Ho lda et al [51], on the basis of LMTO calculations, have estimated a mean value for the spin-up electron energy position of 1.51 eV below the Fermi level. The multielectron 3 T 1 ground state of the Ni 3d 8 electrons is situated 0.5 above the VBM as a deep donor [44] (see table 1).…”

“…The average energy of the deep-donor position is referred to the top of the VBM of ZnSe. The column headings on the right-hand side have the following meanings: (a) the values given by Slater et al [39], which have been calculated for free atoms; (b) the values given by Zunger [44], which have been calculated, for free ions, using the LSD method; (c) the values given by Ho lda et al [48], which have been calculated for Zn 0.5 Me 0.5 Se compounds using the LMTO method; (d) the values taken from table VII in [44]; (e) the values given by Felici et al [26]; (f ) the values given by Langer and Heinrich [43]; (g) the energy position of the e 2 spin-up electrons (below the VBM): (α) the values given by [10,11]; (β) the values given by [11]; and (γ ) the values given by Langer and Heinrich [43]. The Fe 2+ unoccupied states, which hybridize with the CB of host crystal, can be seen in XANES spectra of the Se K edge [40], as a p-like contribution at about 1.7 eV below the CBM of pure ZnSe.…”

“…According to the above analysis, it is easy to ascertain that the t 2 spin-up electrons of Fe 2+ interact strongly with the upper part of the VB of the ZnSe host crystal. Creation by the sixth spin-down electron of the deep donor state in the forbidden energy gap and the ∼25% smaller spin-up-spin-down interaction splitting in Fe 2+ [40,44,48,49] (see also table 1) makes the influence of unoccupied Fe states on the CBs weaker. This can be seen on comparing ZnMnSe and ZnFeSe reflectivity spectra (10% Mn and Fe compositions).…”

“…(3) the spin-up-spin-down exchange splitting of the 3d states is at its maximum for the Mn 2+ ion, and decreases monotonically for the other TMs in the sequences Mn, Fe, Co, Ni, and Mn, Cr, V, Ti [44,48].…”