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In this paper we report on the structural, morphological and magnetic properties of semiconducting GaSe epilayers, grown by molecular beam epitaxy, doped to different iron contents (ranging from 1 to 22 at.% Fe). Our results indicate that iron forms metallic Fe nanoparticles with diameters ranging from 1 to 20 nm embedded in the crystalline GaSe matrix. The Fe incorporation proceeds by segregation and agglomeration and induces a progressive disruption of the lamellar GaSe epilayers. The magnetization as a function of the temperature for zero-field cooling with the magnetic field parallel to the surface of the sample provides evidence of superparamagnetic behaviour of the nanoparticles. Cathodoluminescence experiments performed at room temperature reveal semiconducting behaviour even for samples with Fe concentrations as high as 20 at.%.

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ZnSe-Fe and ZnSe-Co granular films have been successfully obtained by electrodeposition under potentiostatic conditions. Cyclic voltammograms of the solutions containing all precursors of the systems are consistent with anomalous codeposition of the zinc and iron-group metals. Electron microscopy analyses reveal a network of Fe and Co particles dispersed in polycrystalline ZnSe without evidence of intermediate compound formation.Electrochemical deposition is an attractive approach for growing semiconductor compounds as ZnSe 1-6 and different kinds of nanosized heterostructures, 7 because it is an economical technique. Recently, theoretical calculations 8,9 and experimental evidences 10 have demonstrated that a tunnel barrier consisting of ZnSe spacer layer between ferromagnetic electrodes can induce spin-polarization in the tunneling current. Thus, ZnSe-Fe and ZnSe-Co granular films become interesting in view of their potential applications to explore spin-based transport processes.In this paper, we report for the first time the successful preparation of both ZnSe-Fe and ZnSe-Co granular films using electrochemical deposition. Detailed information on the electrochemical experiments and procedures as well as structural characterization are described. ExperimentalZnSe-Fe and ZnSe-Co granular thin films were electrodeposited under potentiostatic conditions on stainless steel substrates. All electrochemical experiments were performed with a galvanostat/ potentiostat ͑EG&G model 273A͒ using conventional stationary parallel-plate system. Stainless steel sheets of 2.0 cm 2 in surface area were used as cathodes, whereas the anode was a platinum disk of 2.8 cm 2 in area. An Ag/AgCl/1 M KCl reference electrode was employed. All potentials thereafter are referred to this electrode. Plating solutions were prepared with reagent grade chemicals ͓ZnSO 4 , SeO 2 , CoSO 4 , and ͑NH 4 ͒ 2 Fe͑SO 2 ͒ 2 ͔ immediately prior to each experiment by dissolving the requisite amount of the precursors in distilled water. All films were deposited at 65°C in cathodic potential of Ϫ1000 mV vs. Ag/AgCl reference electrode from the solutions containing 200 mM Zn, 1 mM Se, and different Fe or Co amounts ͑from 0.25 to 1 mM͒ per liter. The pH factor was adjusted between 1.8 and 2.0 by suitable addition of sulfuric acid. Voltammetric experiments were started at 0 mV with scanning in the cathodic direction and then in the anodic direction with a potential sweep rate of 2 mV/s. Only one cycle was run in each voltammetric experiment.The X-ray diffraction ͑XRD͒ studies were performed using Co K␣ radiation to avoid fluorescence in a conventional BraggBrentano geometry. X-ray photoelectron spectroscopy ͑XPS͒ measurements were carried out using a commercial VG ESCA3000 system with a base pressure of 10 Ϫ10 mbar; while XPS profiles were obtained by sputtering with Ar ϩ ions ͑5 keV, 5 A͒. The spectra were collected using Mg K␣ radiation and the overall energy resolution was approximately of 0.8 eV. Transmission electron microscopy ͑TEM͒ analysis were performe...