EPR ofCr2+in II-VI lattices

Abstract

The EPR spectra of Cr'+ in cubic ZnS, ZnSe, ZnTe, and CdTe, and in hexagonal ZnS and CdS are reported. For each, h, M = +4, +2, +1 transitions are observed allowing complete analysis of the S =2 spin H~~i&tonbe. A static tetragonal Jahn-Teller distortion is observed in all cases.Stress-ali~~ent studies are dcexibed which allow a direct estimate of the Jahn-Teller coupling cod5cients. From these, the magnitudes of the Jahn-Teller energies are esegnated to be~500 cm '. A ligand-field model is developed which satisfactorily accounts for the fine-structure parameters and their large variation from one crystal to another. In this treatment, ligand contributions to the spin-orbit interaction with excited d' terms are also included and found to be important. Strain~upling coefficients, describing the changes in the fine-structure terms under externally applied stress, have been experimentally determined for CdTe (Cr'+). A simple theory for this @feet is developed which includes ligand contributions to the spinwrbit interactions but relies on point-ion estimates for the strain matrix elements. Agreement with experiment is relasoliable for the tetragonal coefficients, but the wrong sign is predicted for the trigonal ca&cients. The calculated trigonal cod5cients for CdS do, however, lief lo'ly tf th Ildeparhuwf It I~y~b. A' th p' H~~i&tonian for Cr'+ in this hexagonal wiirtzite lattice.

Optical and magnetic properties of Fe2+ and Cr2+ in II–VI semiconductors: the Jahn-Teller effect

“…Notice that in contrast to results obtained by others [9][10][11], we have used the free ion value λ for chromium in our fitting procedure, instead of relying on the measurements [8,9] of the Jahn-Teller energy in the ground state orbital triplet. The static JahnTeller distortion in the 5 Γ 3 orbital excited state has been neglected here in agreement with references [7] and [8].…”

“…EPR [7] and optical absorption data [8,9] are consistent with a strong static tetragonal (D 2d ) Jahn-Teller distortion. This situation can be described by assuming that this static JahnTeller interaction is smaller than the crystal field splitting Δ but larger than the spin-orbit interaction (see Fig.…”

The effect of electron-phonon interaction in iron-doped III-V cubic semiconductors

“…Fixing E at 18.9 cm −1 and taking approximate values = 2950.0 cm −1 and λ 1 = −56.0 cm −1 [21], we can now look at the evolution of E JT as a function of the gap mode energy,hω 5 . This is displayed in figure 2(a).…”

Парамагнитные дефекты в кристаллах ZnSe, активированных ионами железа

“…Исследовался кристалл ZnSe с концентрацией железа примерно 10 18 cm −3 . Все образцы были вырезаны из одной були K-900.…”

“…Хотя тригональный центр обнаружен не был, регистрировались резонансные переходы типа 0 ↔ ±1 иона Cr 2+ . ЭПР-спектроскопия иона Cr 2+ (d 4 , 5 D, S = 2) в ZnSe хорошо изучена [10][11][12], и идентификация этой примеси не представляет сложности. Во-первых, угловая зависимость обнаруженных переходов (в ста-тье не показана) свидетельствовала о тетрагональной симметрии центров, что соответствует литературным данным.…”