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Fabrication of IR windows grade zinc selenide by the reactive diffusive process
摘要： The preparation of infra-red windows grade zinc selenide (ZnSe) by the reactive diffusion process between liquid zinc and selenium was the goal of present work. In this regards, high purity zinc and Se elements with a nominal composition of Zn50Se50 were capsulated in quartz ampoule and annealed in the temperature range of 550-950 °C. The wurtzite structure of zinc selenide phase was successfully obtained during annealing process beyond 750 oC. The hexagonal structure of zinc selenide was an unstable phase and totally transformed to the cubic construction by increasing the annealing temperature (950 °C) that is appropriate for infra-red windows application. The formation of zinc selenide phase during the annealing process has been performed by the development of an unceasing layer of porous zinc selenide compound in zinc/ selenium interface. The formation of porous zinc selenide can be associated to the different diffusion constants of selenium and zinc atoms in zinc selenide lattice based on the Kirkendall theory.
关键词： Interfaces,zinc selenide.,Kinetics,Chalcogenides
更新于2025-09-23 15:22:29
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Investigation on annealing temperature-dependent optical properties of electron beam evaporated ZnSe thin films
摘要： This research work is devoted to studying optical properties of zinc selenide (ZnSe) thin films deposited by electron beam evaporation technique and annealed at different temperatures in a nitrogen environment. The structural analysis by X-ray diffraction confirmed that the obtained ZnSe films had cubic zinc-blende structure with preferred orientation along plane (111). Based on Swanepoel's envelope method, some important optical parameters such as absorption coefficient, extinction coefficient, refractive index and optical band gap, were evaluated through the transmission spectrum ranging from 300 to 1500 nm at room temperature. The optical band gap increased from 2.52 to 2.65 eV with the increasing annealing temperature. However, both the thickness and refractive index of the films decreased. In addition, the dispersion parameters of the refractive index and energy were also studied by using Wemple-DiDomenico single oscillator model.
关键词： Optical properties,Thin films,Electron beam evaporation,Zinc selenide,Thermal annealing
更新于2025-09-23 15:21:21
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Photoinduced charge carrier dynamics in a ZnSe quantum dot-attached CdTe system
摘要： A new nanohybrid material is prepared by attaching CdTe nanoneedles (NNs) to surface-modified ZnSe quantum dots (QDs). The NNs and QDs are prepared by a colloidal synthesis method in an aqueous alkaline medium. The surface modification and the attachment of nanostructures are achieved by a bifunctional ligand 3-mercaptopropionic acid (3-MPA). The band gap of the ZnSe QDs is varied by controlling the size of the QDs in order to get the maximum overlap between the absorption band of the CdTe NNs and the emission band of the ZnSe QDs, which is a prerequisite for effective charge/energy transfer. The possibility of photoinduced charge transfer (PCT) and F?rster resonance energy transfer (FRET) from the donor (QDs) to the acceptor (NNs) has been assessed. Very fast (less than 800 ps) PCT and FRET from QDs to NNs occur because the emission band of QDs overlaps with the absorption band of NNs. The calculated large value of the overlapping integral, J(λ) ～4.5 × 1019 M?1 cm?1 nm4, of the donor and the acceptor bands proves the feasibility of energy transfer. These findings suggest that the ZnSe QDs can exchange photoinduced energy with the CdTe NNs effectively over a wide distance in a CdTe–ZnSe nanohybrid.
关键词： quantum dots,zinc selenide,F?rster resonance energy transfer,cadmium telluride,nanohybrid,charge transfer
更新于2025-09-23 15:19:57
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Fabrication of ZnSe/InP Heterojunctions on Flat and Shaped Surfaces of InP Laser Crystals
摘要： We have studied the growth of zinc selenide layers on flat and shaped indium phosphide surfaces. The growth rate of zinc selenide has been shown to depend on substrate orientation. It has been shown that the present results can be useful in designing mesa stripe structures for quantum electronic instruments. We have fabricated mesa stripe laser diodes operating on the absorption band of methane and suitable for producing fiber-optic signal transmission systems.
关键词： methane,semiconductor heterostructures,zinc selenide,laser diodes
更新于2025-09-19 17:13:59
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Equilibria in a ZnCl2–H2O–NaOH System, According to Data from Potentiometric Titration, and Selecting Conditions for the Hydrochemical Synthesis of ZnS and ZnSe Films
摘要： Equilibrium processes that occur in the ZnCl2–H2O–NaOH system are studied via the potentiometric titration of zinc chloride in the 0.00006–1.01 mol/L range of concentrations. Based on mathematical simulations, a number of polynuclear structures and soluble phases are identified in the system. Values of the instability constants of complex forms and the constants of the dynamic equilibria of weakly soluble zinc compounds are calculated, along with their stoichiometric compositions and areas of sustainable existence. Refined boundary conditions are determined, along with areas of the formation of ZnSe and ZnS when they are precipitated using sodium selenosulfate and thiourea, respectively. ZnSe and ZnS layers around 1000 and 200 nm thick are obtained via hydrochemical deposition on glass-ceramic substrates. Based on electron microscopy data, it is concluded that the layers consist of spherical aggregates with mean sizes of around 350–450 nm for ZnSe and 50–200 nm for ZnS, generated from primary particles with sizes of around 20–60 and 20–30 nm, respectively.
关键词： equilibrium processes,zinc selenide,complex formation,zinc sulfide,zinc chloride,potentiometric titration,thin films
更新于2025-09-04 15:30:14
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Influence of the Conditions of the Chemical Bath Deposition of Thin ZnSe Films on Their Morphology and Internal Mechanical Stresses
摘要： ZnSe films up to 2300 nm thick on glass-ceramic supports were prepared by chemical bath deposition in the ZnCl2–Na2EDTA–NaOH–NH2OH·HCl system using sodium selenosulfate as a chalcogenizer. The reflections observed in the X-ray diffraction patterns correspond to the ZnSe (stilleite) phase of cubic (space group F43m) structure with a = 5.610 ± 0.002 ?. As shown by electron-microscopic examination, ZnSe films consist of globular formations tightly adjoining to each other with the mean size of 250–400 nm depending on the deposition conditions. Elemental EDX analysis shows that the films contain, on the average, 43.68 at. % Zn, 30.50 at. % Se, and 25.82 at. % O, with the oxygen concentration somewhat decreasing at a depth of 30 nm. The internal mechanical compression stresses caused by the difference in the thermal expansion coefficients of the ZnSe film and glass-ceramic support were calculated; these stresses depend on the film thickness and at ~1040 nm reach –30.62 kN m–2. The results obtained make it possible to exclude film discontinuities, which can appear with increasing film thickness in preparation of precursor layers, and to choose the optimum support material.
关键词： chemical bath deposition,microstructure,internal mechanical stresses,film morphology,zinc selenide,films,sodium selenosulfate
更新于2025-09-04 15:30:14