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Powered by an inexhaustible supply of solar energy, photoelectrochemical (PEC) nitrogen reduction reaction (NRR) provides an ideal solution for the synthesis of green ammonia (NH3). Although great efforts have been made in the past decades, there are still significant challenges in increasing the NH3 yields of the PEC-NRR devices. In addition to the issues of low activity and selectivity similar to electrochemical NRR, the progress of PEC-NRR is also impeded by the limited increase in NH3 yields as the electrode is enlarged. Here, we propose an editable electrode design strategy that parallels unit photo-electrodes to achieve a linear increase in NH3 yields with electrode active area. We demonstrate that the editable electrode design strategy minimizes the electrode charge transfer resistance, allowing more photo-generated carriers to reach the electrode surface and promote the catalytic reaction. We believe that this editable electrode design strategy provides an avenue to achieve sustainable PEC NH3 production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of ZnSe nanostructures with spherical and flower-like morphology. • Fabrication of ZnSe-based sensors for room temperature NH 3 sensing. • ZnSe with flower-like morphology exhibit superior sensing capabilities. Nanostructured materials, defined by their distinctive physicochemical properties at the nanometer scale, facilitate the innovation of sophisticated applications through their inherent size-dependent phenomena and surface characteristics. In this study, we explore the synthesis of ZnSe nanostructures with distinct spherical and flower-like morphologies by varying the concentration of Ethylenediamine tetraacetic acid (EDTA). Our findings reveal that higher concentrations of EDTA facilitate flower-like morphologies, which provide a large surface area desired for gas sensing applications. Herein, the as-synthesized ZnSe nanostructures were applied for ammonia (NH 3) sensing at room temperature at different concentrations to evaluate their performance. The results obtained indicate that ZnSe nanostructures with flower-like morphology exhibit superior sensing capabilities, demonstrating a good response (ΔR/R air)% of 71 % compared to the 61 % response observed for spherical ZnSe nanostructures for 20 ppm NH 3 gas, measured at room temperature. Additionally, the flower-like ZnSe nanostructures show significantly enhanced response and recovery times, demonstrating their potential as efficient materials for NH 3 detection at room temperature. [ABSTRACT FROM AUTHOR]

Optical absorption spectra of colloidal solutions and films based on ZnSe quantum dots (QD) stabilized with thioglycerol or thioglycolic acid and precipitated on spherical nanoparticles of silicon dioxide are presented and studied. In addition to the usual quantum-size effect, two contributions to the energy of excitons in QD were found. The first (surface effect) occurs in colloidal solutions of QD stabilized by thioglycerol due to the absorption of the thiol –SH group by Zn and Se atoms. The second (polarization effect) is additional and is formed in the solid films of both colloids due to the dielectric mismatch between QD materials and the surrounding matrix. It was shown for the first time that the electronic excitation energy transfer on a spherical surface in dense ZnSe QD array occurs due to the mechanism of strong interaction (hybridization of orbitals) between neighboring QD, which is satisfactorily described by the proposed theoretical model. [ABSTRACT FROM AUTHOR]

ZnSe nanoparticles are prepared by using chemical method in the occurrence of an optically transparent and semicrystalline polyvinyl alcohol polymer matrix. The prepared samples were characterised by different spectroscopic techniques like XRD, SEM with EDS, TEM, optical absorption, photoluminescence and FT-IR spectroscopic techniques. The average crystallite size was found to be 6 nm from the XRD pattern. The morphology of prepared sample was analysed by using SEM and TEM studies. Optical absorption spectrum exhibited the bands which were corresponds to pure ZnSe. Photoluminescence spectrum exhibits the emission band at 431 nm with the excitation wavelength of 350 nm. Functional groups of the prepared sample were observed in the FT-IR spectrum. [ABSTRACT FROM PUBLISHER]

The objective of this study is to explore the electrical and optical characterization of zinc selenide (ZnSe) and zinc sulfide (ZnS) semiconductors as cathode materials of an Infrared image converter. The experiments and simulations have been performed for various converter parameters such as pressure, breakdown voltage, interelectrode distance and illumination. The plasma system has been excited by a dc source, and gas discharge phenomena has been determined under a wide atmospheric pressure range, p. The findings show that ZnS and ZnSe have similar electronic behavior in the image converter in general. The measured discharge currents vary for the two cathodes. In the simulations, the electron mobility, thermal velocity, 3D electron density, space and surface charge density, and mean electron energy have been explored in the Ar-filled converter. It has been proven that the two semiconductors exhibit different properties of discharge, in particular, the mobility of electrons, the ionization coefficients, the breakdown voltages U , thermal velocities of electrons and surface charge densities. According to the experimental and theoretical findings, ZnSe shows better electrical and optical characteristics for the Ar-filled converter. [ABSTRACT FROM AUTHOR]

Abstractauthoren We demonstrate that the selection of a limited number of single excitonic lines from a dense array of epitaxial quantum dots (QDs) can be realized spectrally via resonant energy transfer from a huge number of small QDs toward a limited set of large nano-islands through their excited levels. Optical and transmission electron microscopy studies support this mechanism. Theoretical modeling describes the architecture of quantum levels in the array of CdSe/ZnSe QDs, which enables such a spectral selection. Schematic of resonant energy transfer between QDs shown together with a plan-view TEM image of a QD array. [ABSTRACT FROM AUTHOR]

ZnSe powder was prepared via hydrothermal technique using zinc acetate and sodium selenite as source materials. The prepared ZnSe powder was used for preparing film with different thickness values (95, 135 and 230 nm) via thermal evaporation technique. X-ray diffraction showed that the prepared powder has cubic zinc-blende structure with a space group, F 43m. The high resolution transmittance electron microscope results show that the films are composed of spherical-shaped nanoparticles with a diameter in the range of 2–8 nm. The optical properties of ZnSe films with differing thicknesses are investigated by means of spectrophotometric measurements of the photoluminescence, transmittance and reflectance. The absorption coefficient of the films is calculated and the optical band gap is estimated. The refractive index of the films is determined and its normal dispersion behavior is analyzed on the basis of a single oscillator model, in which oscillator energy, dispersion energy and dielectric constant at high frequency are evaluated. Drude model is also applied to determine the lattice dielectric constant and the ratio of the carriers' concentration to their effective mass. [ABSTRACT FROM AUTHOR]

Structural, morphological and compositional characterizations of zinc selenide nanoparticles (NPs-ZnSe) are discussed in this work. NPs-ZnSe were obtained by colloidal synthesis in aqueous solution at room temperature, atmospheric pressure and without inert atmosphere. The synthesis was carried out using zinc chloride (ZnCl 2 ) and elemental selenium as precursors. A mix of Na 5 P 3 O 10 and NaOH called Extran was used as surfactant. Molar concentration and pH of the aqueous solution were varied to study their effect on the crystalline properties of the nanoparticles. The XRD measurements show that the NPs-ZnSe exhibits a cubic phase structure. The size of the nanocrystals was between 3 nm and 4.7 nm. HRTEM analysis showed that NPs-ZnSe exhibit semi-spherical shape. The presence of zinc and selenium in the NPs-ZnSe was confirmed through EDS measurements. [ABSTRACT FROM AUTHOR]

The ZnSe quantum dots (QDs) were synthesized in an aqueous system by introducing excess Na + ions, which were characterized by Photoluminescence (PL), PL decay curves, UV–Vis absorption spectrum (ABs), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The results indicate that the particle size of ZnSe QDs were about 4 nm when Na + ions were present in excess, which was bigger than that of ZnSe QDs (about 2 nm) synthesized in the solution without Na + ions. An unexpected emission peak around 590 nm was observed when the concentration of Na + ions was high enough in the reaction solution. This emission peak could be attributed to the selenium vacancies (SVs). [ABSTRACT FROM AUTHOR]

This work presents the extensive experimental studies of the X-ray stimulated luminescence, conductivity, phosphorescence and electric current relaxation, and the thermally stimulated luminescence and conductivity of monocrystalline ZnSe. It was found that the luminescence emission band with a maximum at 635 nm is a combination of at least three emission bands and that the appropriate recombination centres implement both electronic and hole recombination mechanisms. We propose an energy model of the traps and recombination centres in monocrystalline ZnSe and show that the majority of the generated free electrons and holes recombine in the luminescence centres with an estimated probability of 94.3% and that only a small fraction (5.7%) of generated charge carriers are accumulated in traps during the X-ray excitation of the ZnSe sample. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) of ZnSe wide-bandgap semiconductor micropowder was studied at a high optical excitation level by pulsed nanosecond N-laser emission. A new emission band that appeared on the long-wavelength edge of the PL spectrum at 40-75 meV from the electron-hole plasma (EHP) band depending on the optical excitation level showed that plasmons could participate in recombination processes in the EHP. Random lasing at 475 nm from submicron-sized crystallites in ZnSe powder was produced by the third harmonic of a YAG:Nd laser with an exciting-radiation threshold intensity of 750 kW/cm. The lasing manifested as a sharp increase of integrated emission intensity, a narrowing of the spectrum, and the appearance in it of localized and extended mode structure. Random lasing was due to feedback of amplified radiation in closely packed active scattering microcrystallites. [ABSTRACT FROM AUTHOR]

In the present work synthesis of ZnSe:Ni nanoparticles using a simple solvothermal method has been discussed. The structural characterizations of as synthesized materials were done by powder X-ray diffraction (XRD), Transmission electron microscope (TEM) and High resolution transmission microscope (HRTEM) imaging techniques, which revealed formation of core–shell nanoparticles with crystallite size 2–4 nm. The structural parameters such as lattice constants, internal strain, dislocation density etc. of ZnSe and Ni doped ZnSe nanocrystals were estimated. Nickel doping in ZnSe host is verified by the Raman spectroscopy. Optical properties were diagnosed by UV–vis absorption and photoluminescence (PL) techniques. The observed blue-shift in UV–vis absorption edge of the prepared sample of ZnSe as compared to its value for the bulk counterpart indicates formation of nanosized particles. PL spectra of Ni 2+ doped samples indicate red-shift and improved emission intensity. [ABSTRACT FROM AUTHOR]

Abstract: ZnSe nanoribbons were synthesized and characterized with microphotoluminescence (μ-PL) spectra and mappings. The μ-PL results show that the near band edge (BE) and the deep defect (DD) level related emissions are predominantly located at the central and the edge region of the ribbons, respectively. Combining with the HRTEM, the DD related emission is attributed to the structure defects mainly located at the edge of the ribbon. It is found that the DD related emission consists of three bands, centered at 635, 560 and 535nm, respectively. The temperature dependent PL spectra further demonstrate that the carriers transfer among the different defect states through the thermally activated mechanism. The results provide more direct evidence about the origin of trap state related emissions in ZnSe nanostructures. [Copyright &y& Elsevier]

Highlights: [•] Multi-walled carbon nanotubes/polyvinyl alcohol conductive substrate was made. [•] Uniform ZnSe nanorods were made by electrochemical atomic layer deposition. [•] The ZnSe nanorods show prominent photoelectric property. [•] The properties of Zn x Se1−x (x =0.33, 0.5, 0.67) are compared respectively. [•] ZnSe has a potential application in optoelectronic nanodevices. [ABSTRACT FROM AUTHOR]

Abstract: Mg2+ doped ZnSe nanoparticles are prepared by facile wet chemical route. N-methylaniline (NMA) is used as a surface passivating agent to obtain the agglomeration free nanoparticles. X-ray diffraction (XRD) pattern exhibits the cubic zinc blende structure of ZnSe. Ultraviolet visible spectroscopy (UV) shows the strong quantum confinement effect and the band gap is 3.56eV. The emission spectrum confirms the incorporation of Mg2+ into the ZnSe. The presence of NMA is confirmed by Fourier transform infrared spectroscopy (FTIR). Transmission electron microscopy (TEM) result shows that the synthesized ZnSe is free from agglomeration and average size of the nanoparticles is about 15nm. EDAX analysis confirms the presence of Mg2+ in ZnSe nanoparticles. [Copyright &y& Elsevier]

Abstract: We have demonstrated nano-structured Cu(In,Al)Se2 (CIAS) near-infrared (NIR) photodetectors (PDs). The CIAS NIR PDs were fabricated on ZnO nanowires (NWs)/ZnO/Mo/ITO (indium tin oxide) glass substrate. CIAS film acted as a sensing layer and sparse ZnSe NWs, which were converted from ZnO NWs after selenization process, were embedded in the CIAS film to improve the amplification performance of the NIR PDs. X-ray diffraction patterns show that the CIAS film is a single phased polycrystalline film. Scanning electron microscopy was used to examine the morphology of the CIAS film and the growth of NWs. Two detection schemes, plain Al–CIAS–Al metal–semiconductor–metal structure and vertical structure with CIAS/ZnSe NWs annular p–n junctions, were studied. The nano-structured NIR PDs demonstrate two orders of magnitude for the annular p–n junction and one order of magnitude for the MSM structure in photocurrent amplification. The responsivities of the PDs using both sensing structures have the same cut-off frequency near 790nm. [Copyright &y& Elsevier]

Abstract: The paper describes the photoelectrochemical studies and the electrochemical synthesis of zinc selenide thin films. Obtained results specify the range of potentials where semiconducting compound is deposited. Photocurrent profiles indicate the p-type conductivity of the electrodeposited semiconductor. The generated photocurrent indicates the anomalous absorption of the light below the band gap range of ZnSe and suggests a plasmon–exciton coupling effect. [Copyright &y& Elsevier]

ZnSe quantum dots (QDs) and flower-shaped nanocrystals (NCs) were successfully synthesised via a cheap, green and nontoxic route, using environmentally friendly N, N-dimethyl-oleoyl amide as the solvent of Se. The experimental results show that the as-prepared ZnSe QDs with a zinc-blende structure have a narrow size distribution and without resorting to any as-synthetic size-selective procedure. A systematic study of the ZnSe QDs formation process indicates the following properties: variation of some reaction parameters allows us to tune the particle sizes and plays a greater role in the determination of the monodisperse characterisation, for example, these parameters include the amount of ligand and precursors, the injection temperature of Se solution. These size tunabilities interpreted well by the growth kinetics. Another interesting result is that the ZnSe QDs aggregate to flower-shaped NCs, and the flower-shaped NCs also have size-dependence quantum effects as the prepared disperse ZnSe QDs. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents results of the photoacoustic (PA) spectral studies of a series of ZnSe crystals with differently prepared surfaces. All samples exhibited the surface absorption connected with defects states located on their surfaces. The quality of the surface preparation is expressed by the surface absorption coefficient spectra of the samples times the thickness of a damaged layer. In this paper both theoretical and experimental photoacoustic amplitude and phase spectra as also the corresponding computed surface and volume optical absorption coefficient spectra of the samples with differently prepared surfaces are presented and discussed. This is the first attempt of the quantitative evaluation of the surface quality of the samples from the photoacoustic experimental spectra. [Copyright &y& Elsevier]

Abstract: Synthesis of triethylamine capped ZnSe nanostructures with bean-like morphology distribution by a simple and inexpensive wet chemical method has been investigated. The main advantage of this method is the use of non-toxic precursors. The synthesized nanostructures have been characterized by powder X-ray diffraction, ultraviolet visible spectrometry, Fourier transform infrared spectroscopy, photoluminescence and atomic force microscopy. The absorption features obtained in the UV absorption spectrum reveal the formation of nanostructures. A significant blue shift from the bulk material was observed from UV absorption and photoluminescence spectra. [Copyright &y& Elsevier]

Abstract: Electrodeposition mechanism of selenium, zinc and ZnSe phase was studied with the electrochemical techniques. The chronoamperometry and voltammetry were combined with quartz crystal microbalance technique to analyse the deposition processes. It was found that they strongly depend on the applied potentials. The deposition of pure Se starts at 0V vs. saturated calomel electrode (SCE) and the efficiency of this process decreases due to H2Se formation and hydrogen evolution when the more negative potentials are reached. The voltammetric and microgravimetric measurements suggest that the deposition of Zn from the bath containing both ions, follows selenium deposition and synthesis of ZnSe is initiated at −0.6V vs. SCE. The chronoamperometric transients combined with microgravimetry confirmed the range of potentials in which Se and ZnSe are deposited. Below −0.84V vs. SCE the formation of H2Se was observed. Then H2Se may react with Zn2+ ions and another mechanism of ZnSe synthesis is possible. [Copyright &y& Elsevier]

Abstract: A ZnSe alloy was prepared by mechanical alloying and annealing at 520 °C for 6 h. Samples were analyzed using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The as-milled alloy had a dark brown color, which turned to the yellow color characteristic of commercial ZnSe products after annealing. After 10 h of milling the alloy exhibited a zincblende structure. The DSC spectrum showed a broad exothermic band related to structural relaxation and an incomplete endothermic peak associated with the sublimation of nanometric ZnSe, corroborated by a second DSC scanning measurement which indicated the presence of amorphous Se as a product of sublimation. XRD and DSC measurements confirmed that the annealing process led to the structural relaxation and sublimation of nanometric ZnSe. As products of sublimation, hexagonal Se and zincblende ZnSe phases were observed. [Copyright &y& Elsevier]

Abstract: The conditions of the electrodeposition of a thin film of polycrystalline ZnSe phase on copper substrate from aqueous baths were studied. The electrochemical behavior of Zn2+ and H2SeO3 species was investigated using cyclic voltammetry. Thin films were deposited potentiostatically on copper substrate and the influence of deposition parameters such as deposition potential, H2SeO3 and ZnSO4 concentration, and temperature of bath on the crystallinity and on the chemical composition of the film is discussed. The ZnSe layers were characterized by X-ray diffraction, X-ray energy dispersive spectroscopy and scanning electron microscopy. [Copyright &y& Elsevier]

Abstract: The rich polymorphism of amphiphilic poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO-b-PPO-b-PEO) block copolymers in selective solvents was employed to form a variety of self-assembled nanostructures and subsequently use them as templates to grow and control the size, morphology, and composition of compound semiconductor nanocrystals. II–VI nano-dots, -wires, -tubes, -plates, and hollow spheres were synthesized by a reaction between a group-II precursor that was pre-dissolved in one of the solvents and hydrogen selenide. Shape control was accomplished by tuning the composition of the template to the phase region of interest thus forming spherical, cylindrical, or planar nanodomains, while size control was achieved by manipulating the group-II concentration in the domains or by changing the domain size within a given phase region. Control over nanocrystal composition was demonstrated by synthesizing ZnSe and CdSe nanocrystals using diethylzinc and dimethylcadmium as the group-II precursor, respectively. The as-grown nanocrystals are optically active and exhibit quantum confinement due to their reduced dimensions. The stability of the templating system was also investigated and the microemulsion breakage temperature profile as a function of the dispersed phase composition was constructed. This is useful for recovery of the nanocrystals from the templating medium and post-processing for integration into functional devices. The technique is scalable and operates at room temperature without requiring mechanical mixing of the reactants to achieve uniform particle growth and monodispersity. [Copyright &y& Elsevier]

Abstract: A numerical simulation of the composition modification induced in ZnSe by nanosecond irradiation of the KrF excimer laser (λ =248nm, τ =20ns) has been carried out. Intensive evaporation of components has shown to results in the material surface cooling and forming a nonmonotone temperature profile with maximum temperature in semiconductor volume at the distance of ∼6nm from the surface. As a result of evaporation and diffusion of components formation of the near-surface layer with nonstoichiometric composition takes place and enrichment of selenium reaches maximum value not on the surface, but in the semiconductor volume. [Copyright &y& Elsevier]

Abstract: The recombination processes around the excitonic region of undoped ZnSe and chlorine doped ZnSe thin films were studied by continuous-wave photoluminescence (cw-PL) and time-resolved photoluminescence (TRPL) spectroscopies. Samples with different chlorine concentration were obtained by varying the temperature of the Cl source. The evolution of the PL signal and its decay time were analyzed as a function of temperature. Activation energy (E a) values associated to the quenching of the D0X and band-to-band emission were obtained from the temperature dependent cw-PL experiments. The activation energy was lower for the film with higher Cl content. The characteristic exponential decay time (τ PL) of the PL signal decreased with increasing Cl concentration. [Copyright &y& Elsevier]

Abstract: The zinc selenide crystals were grown in graphite crucibles by Bridgman–Stockbarger method in vertical compression furnace under argon pressure of . The grown ZnSe(Al,O,Te) single crystals were annealed in a Zn vapor at 1290K for 24h. An X-ray diffractometer (XRD) was used to investigate the structural properties of the zinc selenide single crystals. The lattice constants of the ZnSe single crystals were obtained from XRD data. After annealing it in a Zn vapor at 1290K, it is found that the lattice constant decreases. From the absorption spectra, the band gap energies of the ZnSe single crystals were calculated by a linear fitting process. The band gap energy of the ZnSe(Al,O,Te) single crystal decreases more than that of the ZnSe single crystal. The maximum wavelength of the radioluminescence of the ZnSe(Al,O,Te) scintillator excited by X-ray was 606nm, which was well matched with the response wavelength of the Si photodiode. The energy resolution of the annealed ZnSe(Al,O,Te) scintillator was 13.9% when it was exposed to 137Cs -ray. Its size was . The afterglow level of the annealed ZnSe(Al,O,Te) scintillator after 5ms was 0.014%. The luminescence decay time of the annealed ZnSe(Al,O,Te) scintillator has two exponential components with 4 and time constants. The charged particle and the low energy gamma ray can be detected successfully with the annealed ZnSe(Al,O,Te) scintillator. It was investigated that the ZnSe(Al,O,Te) scintillator can be used for the security inspection system. [Copyright &y& Elsevier]

Abstract: ZnSe films were pulse electrodeposited on conducting glass substrates with and without the addition of phosphotungstic acid. X-ray diffraction studies indicated the formation of single-phase cubic ZnSe. The films possessed low dislocation density. Addition of phosphotungstic acid resulted in films with nanocrystallites. The band gap of the films were found to increase for the films deposited with phosphotungstic acid due to the quantum size effects. Thickness of the films was higher for the films deposited with phosphotungstic acid compared to those deposited without acid. The films had a crystallite size of the order of 15nm and a surface roughness of 1.8nm. The films were found to possess a slight excess of Se as evident from the EDAX measurements. [Copyright &y& Elsevier]

Abstract: A first-principles theoretical study of the structural and electronic properties of ZnSe, BeSe and their alloy, has been performed using the full-potential linear muffin-tin orbital (FP-LMTO) method. The effect of composition on structural properties such as lattice constants and bulk modulus was investigated. It was deduced that increasing the Be composition in the alloy increases the hardness of the material. In addition, from the obtained band structures, the electron (hole) conduction and valence effective masses were deduced. These parameters were found to depend nonlinearly on alloy composition x. Using the approach of Zunger and co-workers, the microscopic origin of band gap bowing has been explained. A reasonable agreement is shown between our results with other theoretical calculations. [Copyright &y& Elsevier]

We present an investigation of the electronic properties and optical constants of zinc-blende ZnSxSe1-x semiconducting alloys at normal and under hydrostatic pressure up to 20 kbar. For this purpose, we used an empirical pseudopotential method within the virtual crystal approximation. The effects of alloy composition are taken into consideration in the calculation, which improves significantly the bandgap bowing parameters with respect to the experiment. Results regarding the composition and pressure dependences of energy bandgaps, electron valence and conduction charge distributions, optical high-frequency dielectric constant and its linear pressure coefficient are presented and discussed. The information derived from the present study may be useful for the development of opto-electronic devices that operate in the blue/green spectral range. [ABSTRACT FROM AUTHOR]

We present an investigation of the electronic properties and optical constants of zinc-blende ZnSxSe1-x semiconducting alloys at normal and under hydrostatic pressure up to 20 kbar. For this purpose, we used an empirical pseudopotential method within the virtual crystal approximation. The effects of alloy composition are taken into consideration in the calculation, which improves significantly the bandgap bowing parameters with respect to the experiment. Results regarding the composition and pressure dependences of energy bandgaps, electron valence and conduction charge distributions, optical high-frequency dielectric constant and its linear pressure coefficient are presented and discussed. The information derived from the present study may be useful for the development of opto-electronic devices that operate in the blue/green spectral range. [ABSTRACT FROM AUTHOR]

Abstract: ZnSe metal–insulator–semiconductor (MIS) photodetectors with SiO2 and Ba0.25Sr0.75TiO3 (BST) insulator layers were fabricated on ZnSe substrates. It was found that dark current densities of these MIS photodetectors were at least one order of magnitude smaller than ZnSe Schottky barrier photodetector without the insulator layers. UV-to-visible rejection ratios of these MIS photodetectors were also large, and the noise equivalent power (NEP) was 1.24×10−13 and 1.9×10−13 for the homoepitaxial ZnSe MIS photodetectors with SiO2 and BST insulator layers, respectively. The corresponding normalized detectivity (D ∗) was 2.55×1012 and 1.67×1012 cmHz0.5 W−1, respectively. These values were better than those observed from the heteroepitaxial ZnSe photodetectors prepared on GaAs substrates. [Copyright &y& Elsevier]

We have demonstrated ZnSe-based white light emitting diodes (LEDs) with longer lifetimes of over 10,000 hr at 14.5A/cm2 by introducing an i-ZnMgBeSe/p-ZnMgSe double cladding structure, which includes a very thin i-ZnMgBeSe layer for suppressing electron overflow and a p-ZnMgSSe layer for efficient p-type carrier concentration. By adopting the double cladding layer instead of only the conventional p-ZnMgSSe cladding layer, rapid degradation is suppressed and the lifetime tendency becomes similar to that of the LEDs consisting of a III-V semiconductor system. The device simulation and the temperature dependence of optical power showed that the i-ZnMgBeSe layer played the main role in increasing electron confinement. Our experimental data and reliability test results indicate that the suppression of the electron overflow is essential to achieve a long lifetime acceptable for practical use. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 154(4): 42–48, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20285 [ABSTRACT FROM AUTHOR]

Abstract: Homoepitaxial ZnSe metal–semiconductor–metal (MSM) photodetectors with ITO, TiW and Ni/Au contact electrodes were fabricated. It was found that barrier heights for electrons were 0.66, 0.695 and 0.715eV for ITO, TiW and Ni/Au on the homoepitaxial ZnSe, respectively. With an incident wavelength of 448nm, it was found that the maximum responsivities for the homoepitaxial ZnSe MSM photodetectors with ITO, TiW and Ni/Au contact electrodes were 120, 50.6 and 28.1mA/W, which corresponds to quantum efficiencies of 33.5, 14 and 8%, respectively. For a given bandwidth of 100Hz and a given bias of 1V, it was found that the corresponding noise equivalent power of our homoepitaxial ZnSe MSM photodetectors with ITO, TiW and Ni/Au electrodes were 8.14×10−13, 1.73×10−12 and 9.25×10−13 W, respectively. Furthermore, it was found that the corresponding D * were 8.7×1011, 4.09×1011 and 7.65×1011 cmHz0.5 W−1, respectively. [Copyright &y& Elsevier]

Abstract: ZnSe thin films were brush plated on substrates maintained at temperatures in the range 30–90 °C from the precursors. The films exhibited cubic structure. Optical band gap of 2.70 eV was obtained. XPS measurements indicated the formation of ZnSe. AFM studies indicated the formation of fine grains of the order of 50 nm, for the films deposited on room temperature substrates. Luminescence emission was observed at 675 nm for an excitation of 450 nm. [Copyright &y& Elsevier]

Abstract: Electrodeposition is emerging as a method for the synthesis of semiconductor thin films and nanostructures, especially chalcogenides and oxides. An overview of the evolutions of researches in this area, as a function of time and material category (IV, III–V, II–VI), is first given. Then key aspects of the electrodeposition of semiconductors, in particular the important role of the free energy of formation of the compounds in the formation process, are recalled. Selected results in the area of the deposition of chalcogenide and oxides, with a focus on CdTe, ZnSe, ZnO and CuInSe2, are presented. The interplay between the formation of a precursor film by electrodeposition and a post annealing treatment is pointed out. Increasing the quality of the precursor film will reduce the need of high temperature annealings and allow to built new materials and new structures, in particular by playing with fragile molecules and templates. [Copyright &y& Elsevier]

Abstract: Semiconductor ZnSe quasi-nanospheres have been successfully prepared by the reaction between Zn2+ and Se2− under the induction of reverse micelles soft template. The products were characterized by X-ray diffraction, transmission electron microscopy and photoluminescence. XRD and TEM revealed that the products were spherical and homogeneous with cubic structure, which ranged from 200 nm to 300 nm in diameter. The corresponding photoluminescence peaks showed a red shift compared to bulk ZnSe. The possible formation mechanism was investigated. [Copyright &y& Elsevier]

We have determined the optical properties of a series of Cl-doped ZnSe epilayers grown on GaAs substrates using ellipsometry and prism coupling. Initially, the carrier concentrations were determined using Hall measurements for samples between 6.30 x 1018 cm-3 and 9.50 x 1018 cm-3. Using a variable angle spectroscopic ellipsometer in the energy range between 0.7 eV and 6.5 eV, we then obtained experimental spectra for each of the samples. By incorporating a three-layer model to simulate the experimental data, we determined the complex dielectric functions for these Cl-doped ZnSe epilayers. In order to facilitate this modeling procedure, we have complemented the ellipsometric results with prism coupling experiments that measured the film thickness and the index of refraction (at discrete wavelengths) very precisely. For the fundamental band gap, we observe a blue shift with respect to the doping concentration, which can be explained by the Burstein-Moss effect. In addition, we have determined the critical point parameters related to these specimens by fitting the second derivatives of both the real and the imaginary parts of the dielectric functions. Similar to several doped III-V semiconductors reported thus far, we find that in Cl-doped ZnSe epilayers, both E1 and E1 + Δ1 red shift, as well as a broadening with respect to the doping concentration. [ABSTRACT FROM AUTHOR]

Abstract: Homoepitaxial and heteroepitaxial ZnSe metal–semiconductor–metal (MSM) photodetectors were both fabricated and characterized. It was found that homoepitaxial ZnSe MSM photodetector could provide us smaller dark current and large photocurrent. With an incident wavelength of 448nm, it was found that the maximum responsivities for the homoepitaxial and heteroepitaxial ZnSe photodetectors were 0.128 and 0.045A/W, which corresponds to a quantum efficiency of 36 and 12%, respectively. Furthermore, it was found that we achieved the minimum noise equivalent power (NEP) of 7.6×10−13 W and the maximum normalized detectivity (D *) of 9.3×1011 cmHz0.5 W−1 from our homoepitaxial ZnSe photodetector. In contrast, NEP and D * of the heteroepitaxial ZnSe photodetector were 2.9×10−12 W and 2.44×1011 cmHz0.5 W−1, respectively. [Copyright &y& Elsevier]

Abstract: Blue light emission of ZnSe thin film from the ZnSe/poly-(N-vinyl-carbazole) (PVK) heterostructures was obtained. The threshold voltage is about 10 V and the brightness of 12 cd/m2 was obtained at 17 V. From the electroluminescence (EL), the photoluminescence (PL), the transient electroluminescence and the dependence of EL intensity on the applied voltage and current, we attribute the EL of ZnSe to carrier injection and recombination. This new phenomenon not only opens a new mechanism of II–IV compounds in low voltage injection EL but also provides a new way of obtaining blue emission. [Copyright &y& Elsevier]

We report the successful growth of ZnSe and ZnTe quantum dots (QDs) embedded in ZnS on GaAs substrate. These QDs have good optical properties and show quantum confinement effect. High-resolution electron scanning microscope studies show that these QDs are grown in Volmer–Weber mode. It is found that the size of the QDs is controlled by the growth duration. When the growth time is short, high density of QDs could be fabricated, but with a long growth time the small QDs get together to form a large cluster. We also show that with this growth method it is possible to grow both ZnSe quantum and ZnTe QDs on one substrate at the same time. For this dual QDs system, two peaks corresponding to the emission from the ZnSe dots (3.0 eV, blue–violet) and ZnTe dots (2.6 eV, green–blue) could be observed at the same time in the photoluminescence measurement. [Copyright &y& Elsevier]

II–VI-O type alloy semiconductor ZnSeO (O composition up to 6.4%) is grown by molecular beam epitaxy. O composition increases with O2 flow rate. Several XRD peaks are observed when O composition is 2–4%, indicating phase separation. Growth at low temperature results in higher O composition. Photoluminescence intensity of ZnSeO lattice matched to GaAs is much stronger than that of ZnSe and peak shifts to lower energies with increasing O composition. Photoreflectance spectroscopy is performed to investigate the band gap energy. The band gap energy investigated by photoreflectance decreases with increasing O composition due to large band gap bowing even when phase separation occurs. The bowing parameter is estimated as 8.4 eV. [Copyright &y& Elsevier]

In this paper we report on the application of Compton scattering technique for the study of bonding in II–VI semiconductor compounds ZnSe, and CdTe. 59.54 keV gamma rays from a 5 Ci Am241 source were scattered by the samples at about 1700 and analysed by the high purity Ge detector. The overall momentum resolution of the spectrum was about 0.6 a.u. Since all abovementioned compounds have same number of valence electrons, so we have compared the ionicity factor in these compounds using equal–valence–electron–density (EVED) profiles. The EVED profiles were also compared with ZnTe. The analysis of EVED profiles of ZnSe and its isovalent compounds namely ZnTe and CdTe shows that the ionocity factor in CdTe is more than ZnSe and ZnTe, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Novel spherical assemblies of ZnSe-containing block copolymer reverse micelles in aqueous solution have been formed by the addition of HSe-solution to mixtures of Zn2+and the reverse micelles soft template Polyacrylonitrile-block-poly (ethylene glycol)-block-Polyacrylonitrile. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-Vis spectrometer. The results of XRD and TEM analyses demonstrated that the products were spherical and homogeneous with cubic structure, which are about 60 nm in diameter. The corresponding UV-Vis absorption peaks showed a blue shift compared to bulk ZnSe. From the position of the absorption edge (λ e), we calculate an actual ZnSe particle diameter of ~5.0 nm. This approach represented a simple method in the synthesis of the polymer micelles shelled with inorganic materials based on using amphiphilic block copolymers. And studies to improve the uniformity of size, shape, and crystal domain will be a focus of future work. [Copyright &y& Elsevier]