Internal Cobalt States and Charge Transfer Transitions in ZnTe:Co Crystals under Pressure

Griebl, E.; Kronschnabl, A.; Krenzer, M.; Müller, Patrick; Gebhardt, W.

doi:10.1002/(sici)1521-3951(199901)211:1<117::aid-pssb117>3.0.co;2-7

Cited by 10 publications

(6 citation statements)

References 12 publications

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“…Such calculation of the charge transfer deformation potential yields the value D ct (± ±0.8 AE 0.07) eV. This value is in good agreement with the value of D ct (± ±1 AE 0.1) eV given by Scho È tz et al [14] for ZnSe(:Ni) It is also the same order of magnitude as those obtained for ZnTe[:Co] (± ±1.3 AE 0.2) eV [13] and ZnS[:Ni] (± ±1.8 eV) [14].…”

Section: Resultssupporting

confidence: 89%

“…a redshifting absorption structure) was found for ZnTe:Mn and interpreted in terms of intra-atomic transitions within the Mn ions or, alternatively, to a charge transfer between the valence band and Mn levels [12]. In the case of ZnTe : Co [13], ZnSe : Ni and ZnS : Ni [14], the observed broad rise was attributed to charge transfer. A charge transfer onset at 2.2 eV has been invoked in an ellipsometric study of ZnSe : Co grown on GaAs [25], in accordance with photocapacitance measurements on this material [26].…”

Section: Resultsmentioning

confidence: 86%

“…It has been suggested in previous works [13,14] that the spectral dependence near the absorption threshold follows a square root law. The theoretical expression derived by Masut and Penchina [27] for allowed transitions between the valence band and the deep levels has been used to fit the absorption data and to obtain a charge transfer threshold energy in those cases.…”

Section: Resultsmentioning

confidence: 93%

“…[13] and [14]) can be justified on the basis of recent band structure calculations. Calculations by Cardona and Christensen [31] yield negative valence band hydrostatic deformation potentials for group IV elements as well as in III±V and II±VI compounds.…”

Section: Resultsmentioning

confidence: 99%

“…On such assumption the absolute pressure shifts of the conduction and valence band edges (or, equivalently, the band deformation potentials a v and a c ) can be separately determined from the pressure dependence of the band-impurity charge transfer [10]. Absorption measurements under pressure on ZnSe : Mn [11], ZnTe : Mn [12], ZnTe : Co [13], ZnS : Ni and ZnSe : Ni [14] have been reported in this sense. A photoluminescence study on L intra-Co transitions in ZnSe : Co has been reported [15] but no transmission measurements on ZnSe : Co under pressure have been carried out until now to our knowledge.…”

Section: Introductionmentioning

confidence: 99%

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Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure

Ferrer-Roca

Segura

Muñoz

2000

phys. stat. sol. (a)

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Optical absorption of the diluted magnetic semiconductor Zn 1± ±x Co x Se (x 0.02) has been measured at room temperature under hydrostatic pressure up to 14 GPa in a membrane diamond-anvil cell. We found two absorption features: (i) an absorption structure in the energy range 1.5 to 1.8 eV, with a negligible pressure shift (i.e. (0.45 AE 0.05) meV/GPa) which we have identified as the Co 2+ (3d 7 ) internal transition 4 A 2 (F) 3 4 T 1 (P) and (ii) an onset in the energy range 2 to 2.7 eV which redshifts with pressure (dE/dP (± ±8.1 AE 0.6) meV/GPa). We have attributed such absorption edge to charge transfer between the ZnSe valence band and the Co 2+ (3d 7 ) levels. On the assumption that those levels are absolute energy references, a valence band deformation potential of (± ±0.8 AE 0.07) eV has been derived.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure

Ferrer-Roca

Segura

Muñoz

2000

phys. stat. sol. (a)

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Pressure dependence of the optical properties of wurtzite and rock‐salt Zn_1–xCo_xO thin films

Sans¹,

Segura

Sánchez‐Royo

et al. 2006

Physica Status Solidi (b)

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In this paper we investigate the electronic structure of Zn 1-x Co x O by means of optical absorption measurements under pressure. Thin films of Zn 1-x Co x O with different Co content (from 1 to 30%) were prepared by pulsed laser deposition on mica substrates. Absorption spectra exhibit three main features that are clearly correlated to the Co content in the films: (i) absorption peaks in the infrared associated to crystal-field-split internal transitions in the Co 3d shell, with very small pressure coefficients due to their atomic character; (ii) a broad absorption band below the fundamental edge associated to charge transfer transitions, that exhibit relatively large pressure coefficients, indicating that the Co 3d final states must be strongly hybridized to the conduction band; and (iii) a blue-shifted fundamental absorption edge associated to band to band transitions with a pressure coefficient close to that of pure ZnO. In the up-stroke the transition pressure from wurtzite to rock-salt phase decrease almost linearly as the Co increases, from 9.5 GPa in pure ZnO to about 6.5 GPa for x = 30%. In the down-stroke pressure we observe a similar behavior, yielding a metastable rock-salt phase at room pressure, after a pressure cycle up to 15 GPa.

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Optical absorption spectra of substitutional Co ²⁺ ions in Mg _x Cd _{1–
x} Se alloys

Jin

Kim

Jang

et al. 2006

Phys. Status Solidi (c)

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Optical absorption spectra of substitutional Co 2+ ions in Mg x Cd 1−x Se alloys were investigated in the composition region of 0.0 ≤ x ≤ 0.4 and in the wavelength region of 300 to 2500 nm at 4.8 K and 290 K. We observed several absorption bands in the wavelength regions corresponding to the 4 A2( 4 F) → 4 T1( 4 P) transition and the 4 A2( 4 F) → 4 T1( 4 F) transition of Co 2+ at a tetrahedral T d point symmetry point in the host crystals, as well as unknown absorption bands. The several absorption bands were analyzed in the framework of the crystal-field theory along with the second-order spin-orbit coupling. The unknown absorption bands were assigned as due to phonon-assisted absorption bands. We also investigated the variations of the crystal-field parameter Dq and the Racah parameter B with composition x in the Mg xCd1−xSe system. The results showed that the crystal-field parameter (Dq) increases, on the other hand, the Racah parameter (B) decreases with increasing composition x, which may be connected with an increase in the covalency of the metal-ligand bond with increasing composition x in the Mg xCd1−xSe system. 1 Introduction Mg x Cd 1−x Se, one of the Mg-based II-VI semiconductors, has been expected as a useful alloy system for optoelectronic device applications in the range of the whole visible spectrum between the band gap energy 1.7 eV of CdSe and 3.6 eV of MgSe [1,2]. The alloy system has the possibility for the tuning of band gap and lattice constants by varying the Mg concentration so that they can easily be matched with III-V alloy substrates for device applications. In recent investigations of optoelectronic materials, 3d transition metal impurities have aroused a great deal of interest. The transition metal impurities have been known to introduce deep levels in band gaps of semiconductors. These levels not only control number, type and mobility of conducting carriers, but also act as activators or killers in luminescent materials. However, there has been no exact understanding of the optical properties of the transition metal impurities in Mg x Cd 1−x Se alloy system. Also, the Mg x Cd 1−x Se system of the A x B 1−x C ternary type is suitable to obtain further information on the optical transitions due to the transition metal centers in optoelectronic materials, because it gives a great deal of variations in the degree of the crystal-field between a transition metal atom and its ligands with composition x.In this paper, we report the results of the optical absorption spectra of substitutional Co 2+ ions in Mg x Cd 1−x Se alloys, and their fine structures were analyzed in the framework of the crystal-field theory.

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Internal Cobalt States and Charge Transfer Transitions in ZnTe:Co Crystals under Pressure

Cited by 10 publications

References 12 publications

Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure

Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure

Pressure dependence of the optical properties of wurtzite and rock‐salt Zn_1–xCo_xO thin films

Optical absorption spectra of substitutional Co ²⁺ ions in Mg _x Cd _{1–
x} Se alloys

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Internal Cobalt States and Charge Transfer Transitions in ZnTe:Co Crystals under Pressure

Cited by 10 publications

References 12 publications

Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure

Optical Absorption of Zinc Selenide Doped with Cobalt (Zn1-xCoxSe) under Hydrostatic Pressure

Pressure dependence of the optical properties of wurtzite and rock‐salt Zn1–xCoxO thin films

Optical absorption spectra of substitutional Co 2+ ions in Mg x Cd 1– x Se alloys

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Product

Resources

About

Pressure dependence of the optical properties of wurtzite and rock‐salt Zn_1–xCo_xO thin films

Optical absorption spectra of substitutional Co ²⁺ ions in Mg _x Cd _{1–
x} Se alloys