Ultraviolet photoemission study of electronic structure of Cd_1-xM_xSe (M - Mn, Fe, Co) semimagnetic semiconductors

Abstract

The electronic structure of semimagnetic semiconductor ternary alloys Cd,_,M,Se (M = Mn, Fe, CO) crystals was investigated by photoemission. The ground state of impurity level of Fe 3d6 and CO 3d7 were found to determine the position of the edge of the valence band of the ternary alloys crystals Cd, -,Fe,Se and Cd,-,Co,Se. The core level Se 3d spectra measured for Cd, -,Fe,Se crystals with different composition x correspond to the apperance of local structure in the crystal. The valence band density of states distribution was estimated for MnSe, FeSe and CoSe with CdSe structure as a difference between valence band density of states distribution for Cd,-,Mn,Se, Cd,-,Fe,Se or Cd,-,Co,Se respectively and CdSe.

Resonant Photoemission Spectra of Zn1-xCoxS Valence Band

“…The only two particularities which can be revealed are: a clearly resolved maximum at the edge of the valence band and a flat maximum at about 4 eV below the edge. While the first closely reminds the maxima observed at the edges of the valence bands for other Fe-and Cocontaining SMSCs [3], the latter is in contrast with the pronounced maxima derived from TM 3d states usually revealed in the middle of the valence band for Hg-and Cd-based SMSCs [3,9]. The feature observed at the edge of the valence band is connected with presence of the sixth (in Fe) or sixth and seventh (in Co) electrons in TM 3d shell.…”

“…Since photoemission spectroscopy was well known as a useful tool for band stucture investigations it was quite early applied for reveading TM 3d contribution to the valence band of SMSC [2]. The band mapping techniques show clearly some band structure modifications induced by presence of TM 3d states, but for relatively low photon energies usually used in these methods (20-40 eV) additional density of 3d states manifests itself relatively weakly [3]. Fortunately, some complementary data can be acquired by means of resonant photoemission technique, successfully applied in studies of electronic stucture of open-shell metal compounds [4].…”

Electronic Structure of Diluted Semimagnetic Semiconductor (Cd,Co)Se

“…Two broad maxima were found -one at the edge of the valence band (-0.8 eV) and the second nearly in the minimum of the CdSe density of states (-3.5 eV). Thus, the Co 3d electrons contribute to the valence band of mixed crystal in a similar way as the Fe 3d electrons in Fe-based SMSC [4,7], in contrast to the case of the traditional Mn-based systems [4,7].…”

Fe 3d Contribution to Hg1-xFexSe Valence Band by Means of Angle-Resolved Photoemission

“…This additional density of states corresponds to the contribution of the Fe 3d electrons. This kind of contribution appears as well in near the same region of the valence band of Cd1x Fex Se [7][8][9][10][11].…”

“…The simple quantitative results of calculation of energy levels of Fe 2 + ion in hexagonal environment was recently presented by Twardowski [4]. The Mn 3d electrons contribute to the valence band but they are not giving any contribution over the valence band edge of II-VI compounds [5,6] while Fe 3d electrons contribute as well in the valence band as over the edge of II-VI compounds valence band [7][8][9][10][11].…”