Analysis of the donor-acceptor recombination band in the photoluminescence spectra of CuInSe2

International audienceAn empirical relation is proposed to analyze the broad band observed in the photoluminescence spectra of CuInSe2 (CIS) due to donor-acceptor pair recombinations. This permits, together with the knowledge of the majority carrier concentration and the compensation ratio, the determination of the activation energy ED of the donor and EA of the acceptor levels and the mean distance R between D-A pairs. Values of the dielectric constant ϵ, ED and EA for CIS obtained with this model agree with reported data

Crystallographic characterization and magnetic properties of the MnIn2Ga2zSe4 alloy system

X-ray powder diffraction, differential thermal analysis DTA and magnetic susceptibility χ measurements were carried out on polycrystalline samples of the alloy system MnIn2(1−z)Ga2zSe4. Magnetization measurements at 2 K in magnetic fields up to 35 T were made on the MnIn2Se4 and MnGa2Se4 compounds. From the lattice parameter values, the limits of single-phase solid solution were estimated. At room temperature, the solid solutions extend over the range 0<z<0.30 for the δ-phase and from 0.75 to 1.0 for the η-phase. Values of TN, the Néel temperature, were obtained from the cusp in the χ versus T curves. Values of Curie–Weiss temperature θ were determined from the 1/χ versus T curves for the single-phase samples in each range. The magnetic results indicate that for 0<z<0.30, the Mn is randomly distributed over the cation sublattice, the phase having space group and the compound MnIn2Se4 (z=0) was found to be spin-glass, with Tg=2.75 K and θ=−94 K. The high z single phase η alloys show an ordered distribution of the Mn2+ ions on the cation sublattice and were antiferromagnetic showing ideal Curie–Weiss behavior, with TN=8 K and the Curie–Weiss temperature θ=−24 K

Magnetic properties for the Mn2GeTe4 compound

Measurements of magnetic susceptibility χ, in the temperature range from 2 to 300 K, and of magnetization M vs. applied magnetic field B, up to 5 T, at various temperatures were made on polycrystalline samples of the Mn2GeTe4 compound. It was found that Mn2GeTe4 has a Néel temperature TN of about 135 K, shows mainly antiferromagnetic behavior with a very weak superimposed ferromagnetic component that is attributed to spin canting. Also, the magnetic results suggest that a possible spin-glass transition takes place at Tf≈45 K. The spin-glass order parameter q(T), determined from the susceptibility data, was found to be in agreement with the prediction of conventional spin-glass theory. The M vs. B results indicated that bound magnetic polarons (BMPs) occur in the compound, and that the effects from BMPs disappear at approximately 80 K. The M vs. B curves were well fitted by a Langevin type of equation, and the variation of the fitting parameters determined as a function of temperature. Using a simple spherical model, the radius of the BMP in the material was found to be about 27 Å; this value is similar to the effective Bohr radius for an acceptor in the II-IV-V2 and I-III-VI2 ternary semiconductor compounds. © 2008 Elsevier B.V. All rights reserved.Fil: Quintero, M.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Quintero, E.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Caldera, D.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Moreno, E.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Morocoima, M.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Grima, P.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Ferrer, D.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Marchan, N.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Bocaranda, P.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Delgado, G. E.. Universidad de Los Andes Facultad de Ciencias; VenezuelaFil: Henao, J. A.. Facultad de Ciencias; ColombiaFil: Macías, M. A.. Facultad de Ciencias; ColombiaFil: Pinto, J. L.. Facultad de Ciencias; ColombiaFil: Ponce Altamirano, Claudio Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentin