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Abstract Colloidal quantum dots (QDs) are attracting research interest because of their unique optical properties that result from the quantum confinement effect. ZnSe QDs, which are II–VI semiconductors, offer a wide direct bandgap (2.7 eV), making them promising for applications such as light-emitting diodes, photodetectors, and biomedical labeling. In the present work, colloidal ZnSe (QDs) were synthesized by the hot-injection method with a Zn:Se ratio of 1:1. The optical properties of ZnSe QDs obtained at different reaction times were investigated by spectrophotometric UV–vis absorption and emission measurements. The as-synthesized ZnSe QDs exhibit blue excitonic emission, and no defect emission was detected. Transmission electron micrographs indicated that the QDs have a spherical morphology with dimensions ranging from 3.69 to 4.53 nm. In particular, the Brus model was applied to demonstrate a correlation between the QD sizes and the optical bandgaps obtained from Tauc plots.

Electronic and optical properties of graphene-like ZnSe were investigated through a comprehensive study using ab initio calculations. By employing the GW method, we accurately determine the electronic band structure and bandgap of graphene-like ZnSe, considering the many-body effects. Additionally, we examine the optical properties of graphene-like ZnSe using the GW+BSE method, calculate the optical absorption spectrum, and determine excitonic properties such as exciton binding energy and optical bandgap. The GW calculations reveal that the ZnSe bandgap is direct with an energy gap of approximately 4.869 eV and exhibits excitons with relatively strong binding energies ranging from 0.2 to 0.8 eV. The majority of bound exciton distributions arise from transitions between Zn(3p)+Zn(3d)+Se(4p)→Zn(4s)+Se(4s) at the gamma point of the Brillouin zone. The precise determination of the band structure, bandgap, and excitonic properties enables a better understanding of the material's behavior and aids in the design and optimization of future ZnSe graphene-based devices. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots (QDs) are attracting research interest because of their unique optical properties that result from the quantum confinement effect. ZnSe QDs, which are II–VI semiconductors, offer a wide direct bandgap (2.7 eV), making them promising for applications such as light-emitting diodes, photodetectors, and biomedical labeling. In the present work, colloidal ZnSe (QDs) were synthesized by the hot-injection method with a Zn:Se ratio of 1:1. The optical properties of ZnSe QDs obtained at different reaction times were investigated by spectrophotometric UV–vis absorption and emission measurements. The as-synthesized ZnSe QDs exhibit blue excitonic emission, and no defect emission was detected. Transmission electron micrographs indicated that the QDs have a spherical morphology with dimensions ranging from 3.69 to 4.53 nm. In particular, the Brus model was applied to demonstrate a correlation between the QD sizes and the optical bandgaps obtained from Tauc plots. [ABSTRACT FROM AUTHOR]

In this work, ZnSe-based polycrystalline ceramics were successfully synthesized from Se and Zn powders in the range of 2.0 GPa and 900 °C–1400 °C by using the high-pressure and high-temperature (HPHT) method. From the acquired experimental results, it was revealed that the fabricated samples were composed of ZnSe with a sphalerite structural type. More specifically, the samples consisted of lamellar and granular grains, and the stomata of the samples showed a trend of first increasing and then decreasing as a function of the elevated temperature. In addition, the infrared transmittance of ZnSe ceramics in the 4 to 18-μm range increased and then decreased by increasing the temperature. When the temperature exceeded the value of 1000 °C, the internal zinc surplus and selenium deficiency of zinc selenide ceramics induced a decrease in the mechanical and optical properties of the ceramics. By optimizing the conditions of the experimental process, the ZnSe synthesized at 1300 °C exhibited better performance with a transmittance of 55%. [ABSTRACT FROM AUTHOR]

Nanoparticles of zinc selenide (ZnSe) were produced by an innovative, uncomplicated, and extremely rapid process that took no longer than a few seconds. For the production of zinc ions, zinc chloride was utilized, and selenium was used for the production of selenium ions. The effect of Zn to Se ions ratio on optical properties has been examined. The prepared nanoparticles were tested and characterized by using transmission electron microscope TEM, scanning electron microscope SEM and UV–Visible spectroscopy. The morphological results revealed that the ZnSe has a spherical shape with mean diameter around 15 nm and the band gap of the ZnSe increases with increasing the Zn content in the sample. The prepared materials were tested as antibacterial agent. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition (CVD) ZnS and ZnSe have high infrared transmittance and good optical and mechanical properties, and are the preferred infrared optical materials for infrared military detection systems. The preparation of largesized and highly homogeneous ZnS and ZnSe materials is an important topic for future research. This article introduces the principle of chemical vapor deposition and the main problems in the accumulation process, describes the necessary optical properties of high-performance infrared materials, summarizes and analyzes the research progress of CVD ZnS and CVD ZnSe, and main defect formation mechanism of the two materials as well as the process control research. It aims to improve the production process parameters and provide theoretical reference for the batch preparation of high-performance ZnS and ZnSe materials for military applications. [ABSTRACT FROM AUTHOR]

Gamma-ray and neutron irradiation tests were performed by using antireflective-coated and non-antireflective-coated samples of ZnSe and ZnS to examine the impact on their infrared optical properties. In neutron irradiation tests, ZnSe and ZnS samples showed minimal transmittance reduction even up to 1.44 × 1016 n/cm2 (evaluated by dpa value, the values are 5.77 × 10−6, 2.07 × 10−5 for ZnSe and ZnS, respectively), about 5.8 times higher than the expected neutron fluence in ITER. Gamma irradiation at 100 kGy did not affect any of the samples, however, at 5.6 MGy (2.6x the expected dose of ITER), non-antireflective-coated ZnSe and ZnS exhibited induced absorption bands. Antireflective coating did partially mitigate this effect, but ZnS, even with antireflective coating, showed up to 2.5 % degradation over the wide wavelength range of 1.5–4.5 µm, whereas ZnSe was less affected. Both ZnSe and ZnS exhibited a modest 2 % absorption around 3 µm. Surface analysis by SEM, laser microscope, and XPS linked the 3-µm degradation to gamma-irradiation-induced Zn(OH) 2 formation that was confined to the surface. Thus, transmittance degradation of ZnSe over the lifespan of ITER was estimated to be a maximum of approximately 7.8 %. The practical use of ZnSe in the IRTh system requires further evaluation with Si and CaF 2 lenses and for the optical design to be finalized. Nevertheless, these findings suggest that ZnSe is a promising candidate for the IRTh system's lenses. [ABSTRACT FROM AUTHOR]

Zinc Selenide (ZnSe) as an important II-VI semiconductor and one of the first semiconductors discovered with a band gap of around 2.7 eV at 25 °C. ZnSe thin films have been deposited by e-beam evaporation method with different thicknesses from 50 nm to 150 nm and effects of annealing temperature on optical and electrical properties of thin films have been investigated at room temperature (RT), 100°C and 200°C. It has been found that the energy bandgap of semiconductor thin films tend to decrease as the temperature increases. Optical properties of the synthesized films were investigated by UV-VIS spectrometer in the wavelength range of 400-1000 nm. Energy band gap of films were calculated and variation due to variation in the thickness were observed. The least band gap value was found to be 1.92 eV for 150 nm thin at 200°C. The band gap results show the semiconducting nature of films grown. XRD technique was used to study the structural properties and the Hall measurement and I-V characteristics were used to study the electrical properties of the thin films. Hall characteristic of the ZnSe thin films for 150 nm at room temperature show that the material has p-type semiconducting nature which remains same if annealed to 200°C. [ABSTRACT FROM AUTHOR]

Chalcogenide nanostructures are the materials with diverse applications. Here, we report rapid hydrothermal synthesis of crystalline ZnSe quantum dots (QDs), avoiding the use of toxic chemicals. To the best of our knowledge, this is the first report on very rapid (5 h) hydrothermal synthesis of pristine ZnSe QDs. Elemental selenium is used as a source for selenium. Structural, morphological, compositional, and optical properties of the semiconductor were studied. Structural properties (X-ray diffraction) demonstrate that the particles have grown in a single cubic phase. Morphological studies show formation of agglomerated QDs (4 nm). The material possess stoichiometric ratio of the constituent elements that are uniformly distributed. Selected area electron diffraction (SAED) study indicated the material is polycrystalline in nature. Optical properties demonstrated that the QDs are suitable for optoelectronic devices exhibiting room temperature photoluminescence. Commission Internationale de l'Éclairage (CIE) chromaticity diagram shows the material exhibits violet emission and hence suitable for violet LEDs that have potential ability in clinical applications. [ABSTRACT FROM AUTHOR]

• Toxic-free Mn-doped ZnSe quantum dots were synthesized and control by zinc precursors. • ZnSe quantum dots were doped with Mn2+ ions through the nucleation doping process. • 4T 1 to 6A 1 transition by Mn2+ allows the narrow emission region of the violet-blue of ZnSe to extend to the orange region. • Correlation between structure and optical properties of doped quantum dots was investigated. We have successfully demonstrated the colloidal hot-injection process to easily obtain the Mn-doped ZnSe quantum dots (QDs) with a size of about 4–5 nm, and d -spacing is 0.31 nm, corresponding to the (1 1 1) lattice plane of ZnSe. Experimental results show that UV–vis absorption and fluorescence spectra were recorded to elucidate the role of Mn2+ ions substituted into ZnSe, which resulted in the carrier transfer of luminescent sites by a small amount of Mn2+ dopant. The small size of the Mn-doped ZnSe QDs offers intriguing opportunities for their application in photonic, bioimaging, and spintronics devices. [ABSTRACT FROM AUTHOR]

ZnSe powders have been prepared by vapor reaction during combustion synthesis. The powders contain both cubic and hexagonal ZnSe, where the fraction of the hexagonal phase increases with increasing distance from the evaporation source. The powders consist of spherical particles and rod-like crystals with sizes from submicron to a few microns. In UV–Vis region, the ZnSe powders have two absorption edges at 450–500 nm and 650–700 nm, likely connected with intrinsic band-gap transition and defect energy levels. From the optical absorption data, the band-gap of the ZnSe powders is estimated to be 2.4–2.5 eV. Under an UV or blue excitation, the ZnSe powders show very weak near-band-edge emission but strong defect-induced red emission. It appears that the ZnSe powders synthesized by vapor reaction clearly differ from the bulk ZnSe sample by melt solidification in both phase composition and optical properties. [ABSTRACT FROM AUTHOR]

In this article, we report the effects of insertion of yttrium, gold and yttrium-gold (YAu) metallic nano-slabs on the structural, optical and dielectric properties of ZnSe thin films. The ZnSe thin films which are prepared by the thermal evaporation technique under vacuum pressure of 10-5 mbar exhibit hexagonal structure. While the insertion of the 70 nm thick Y layers does not alter the lattice parameters and stress values, the Au and YAu layers increased the lattice parameters along the a- and c-axes and decreased the stress values. In addition, the insertion of these metallic layers slightly alters the value of the energy band gap and increases the width of the interbands. The light absorbability are increased by 1.4, 2.0 and 2.4 times upon insertion of Y, Au and YAu, slabs, respectively. On the other hand, the dielectric and optical conductivity analyses has shown that the use of the YAu stacked metal layers increases the real part of the dielectric constant, the optical conductivity, the drift mobility and extended the plasmon frequency range from 35.1 to 254.0 (Ωcm)-1, from 1098 to 1766 cm2/Vs and from 0.94-3.11 GHz to 2.13-4.83 GHz, respectively. The insertion of the two stacked metallic layers between two layers of ZnSe makes the ZnSe more appropriated for thin film transistor technology. [ABSTRACT FROM AUTHOR]

Abstract We demonstrate the growth of ZnSe microspheres in large quantities by using a mixture of Zn and Se as precursors via direct current arc discharge method without the addition of any catalyst or template. The as-obtained samples were characterized by X-ray diffraction, Raman, energy-dispersive X-ray spectrometry, scanning and transmission electron microscopy, and ultraviolet-visible reflectance spectroscopy. The majority of the ZnSe microspheres which were composed of ZnSe nanoparticles exhibited perfectly spherical morphology and a distinct hollow structure with a relatively rough surface. The growth mechanism of ZnSe hollow microspheres has been discussed. Room-temperature excitation and emission spectra as well as the fluorescence lifetime of ZnSe hollow microspheres were measured and the results showed ZnSe hollow microspheres exhibit an intensive wide broad emission bands from 550 to 750 nm upon 470 nm excitation with fast decay time 1.09 ms and CIE chromaticity coordinates (0.65, 0.34), which was ascribed to characteristic structure defects (vacancies and interstitials) in ZnSe. Additionally, the temperature dependent emission behavior was measured and discussed. [ABSTRACT FROM AUTHOR]

• A green and simple synthesis of ZnSe/ZnS quantum dots in aqueous solution was presented. • The influences of synthesis parameters on structure and optical properties of the particles were investigated in details. • ZnSe/ZnS showed better luminous intensity and lifespan than ZnSe and blue luminous. The core-shell quantum dots of ZnSe-ZnS were synthesized in aqueous solution using glutathione (GSH) in an environmentally friendly way. The effects of the concentration of GSH, the synthesis temperature and the NaOH concentration (pH) on the microstructural and optical properties of the prepared core-shell systematically were investigated. Analysis of the XRD patterns and TEM particle images confirmed that the round-typed ZnSe-ZnS quantum dots of size 3 to 5 nm were formed. Comparing to the single core ZnSe, the core-shell ZnSe-ZnS showed an increase in photoluminescence (PL) emission intensity up to 130%. In addition, the core-shell quantum dots showed a good long-term stability maintaining their high PL intensity for at least 84 days. The synthesis process optimization was discussed in detail. The light emission intensities of the quantum dots were dependent on the GSH concentration. The optimum GSH concentration for the core-shell synthesis was found to be around 0.1 mmol. High temperature above 70 C for the core-shell synthesis generally improved the optical properties. However, light discharge characteristics were correlated with the core-shell synthesis temperature and the pH in solution. At the high temperatures of 70 °C and 90 °C, the emission intensities were degraded with high pH of 13 due to the dissociation of the ligand were accelerated. The optimized ZnSe-ZnS quantum dots showed high color purity emitting blue fluorescence light of 378 nm with the narrow full width at half maximum (FWHM) less than 20 nm. Optimization of synthesis parameters showed the possibilities of the simple and eco-friendly manufacture of long term stable and efficient ZnSe-ZnS core-shell quantum dots in aqueous solutions for display applications. [ABSTRACT FROM AUTHOR]

Nanostructured ZnSe/ZnS multilayer thin films with excellent blue light emission were prepared using the electron beam evaporation technique. The structures and crystallization of the nanostructured ZnSe/ZnS multilayer thin films were studied by X-ray diffraction, which revealed a good crystallization with cubic structure of ZnSe and wurtzite structure of ZnS. The surface and inner morphologies of these films were analyzed by the Scanning Electron Microscopic and Transmission Electron Microscope, respectively. Optical transmission spectra were also investigated by UV–vis–NIR scanning spectrophotometer. Furthermore, the blue emission spectra of annealed films locating at about 440 nm were obtained, which corresponded to near band-edge emission of ZnSe. An obvious blue-shift of near band-edge emission was observed with annealing temperature increasing due to the quantum confinement effects. It is full of great potential for the nanostructured films to be used in optoelectronic devices based on outstanding blue luminescence performance. [ABSTRACT FROM AUTHOR]

The various mole percent (1-5%) of Eu-doped ZnSe thin films were fabricated on the indium-doped tin oxide (ITO) conducting glass substrate by single-step electrochemical deposition (ECD) process in an aqueous medium at 50 °C. The structural, optical, magnetic, and electrochemical properties were characterized as a function of the Eu ion concentration. The X-ray diffraction (XRD) analyses evidenced that the films were hexagonal wurtzite structure along with the (101) preferential orientation. High-resolution scanning electron microscopy (HRSEM) results revealed that the thin films show a spherical like structure for 1-3% of Eu-doped ZnSe films. Further, increasing of Eu concentration (4 and 5%), the surface morphology of thin films was observed as agglomerated grain-like structure. The band gap energy of Eu-doped ZnSe thin films (2.35 to 2.49 eV) determined by UV-Vis spectra showed a blue shift of absorption edge compared to the pure ZnSe thin film (2.33 eV). The increased band gap by doping of Eu is due to the quantum size effect. The PL emission intensity enhanced by increasing Eu concentration which revealed the enhanced radiative recombination in the luminescence process. The magnetic study revealed that Eu-doped ZnSe thin films were ferromagnetic in nature. Electrochemical impedance analysis indicated that 4% of Eu-doped ZnSe thin films showed a lower charge transfer resistance (352 Ω) and excellent properties compared to the other samples. Further, the photoelectrochemical measurements carried out for the optimized 4% Eu-doped ZnSe thin film revealed the faster migration of photoinduced charge carriers. The present investigation demonstrates that the electrochemically deposited Eu-doped ZnSe thin film is a promising candidate for electrochemical device applications. [ABSTRACT FROM AUTHOR]

In this study, ZnSe and ZnSe:Cu quantum dots (QDs) were synthesized using Na2SeO3 as the Se source by a rapid and room temperature photochemical (UV-assisted) approach. Thioglycolic acid (TGA) was employed as the capping agent and UV illumination activated the chemical reactions. Synthesized QDs were successfully characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and UV-visible (UV-vis) spectroscopy, Fourier transform-infrared (FT-IR), and energy dispersive X-ray spectroscopy (EDX). XRD analysis demonstrated the cubic zinc blend phase QDs. TEM images indicated that round-shaped particles were formed, most of which had a diameter of about 4 nm. The band gap of the ZnSe QDs was higher than that for ZnSe in bulk. PL spectra indicated an emission with three peaks related to the excitonic, surface trap states and deep level (DL) states. The band gap and QD emission were tunable only by UV illumination time during synthesis. ZnSe:Cu showed green emission due to transition of electrons from the Conduction band (CB) or surface trap states to the 2T2 acceptor levels of Cu2+. The emission was increased by increasing the Cu2+ ion concentration, such that the optimal value of PL intensity was obtained for the nominal mole ratio of Cu:Zn 1.5%. [ABSTRACT FROM AUTHOR]

The ZnSe quantum dots in a matrix of nanoporous carbon are synthesized in the work. For this purpose, nanoporous carbon was synthesized with the required pore size distribution. From the received photoluminescence spectra, it was found that the peak near the band edge in the excitation spectrum can be assigned to the highest transfer efficiency of photogenerated carriers at the correlated sub-band states (about 34 meV below the conduction band of ZnSe) to the deep center states. [ABSTRACT FROM AUTHOR]

Pure (ZnSe) and europium doped (ZnSe:Eu) zinc selenide films were evaporated onto glass substrates using the close-spaced vacuum sublimation (CSVS) technique at different deposition conditions (substrate temperature). The fundamental optical parameters such as optical density, extinction coefficient, refraction index, real and imaginary parts of optical dielectric constant, band gap were evaluated in transparent region of transmittance and absorbance spectrum. Optical spectroscopy analysis shown that in both cases deposited films had a high level of transmittance values (55-65 % for ZnSe films and 80-90 % for ZnSe:Eu films). Moreover, evaluated values of the films optical band gap were in the range of Eg = (2.63-2.69) eV for ZnSe films and Eg = (2.77-2.81) eV for ZnSe:Eu for films with increasing of the films substrate temperature. Fourier-transformed infra-red (FTIR) analysis of deposited ZnSe and ZnSe:Eu films shown that all investigated samples are well-crystalline and identified vibrations are typical for II-VI semiconductors. [ABSTRACT FROM AUTHOR]

Based upon the first principal spin density functional calculation, the electronic, magnetic and optical properties of ZnTMSe and ZnMnTMSe where TM=Fe, Cr, Co are studied using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) method within the local density (LDA)and the self-interaction-corrected(SIC) approximation. The purpose of this study is to determine the effect of different type of dopant and concentration on ferromagnetic and half metallic behavior of ZnSe. Therefore the magnetic disorder local moment (DLM) and the ferromagnetic state are investigated for different concentrations of Mn, Fe, Cr and Co; also the advantages of co-doped ZnSe with TM elements, behavior at room temperature are discussed. The electronic structure and optical properties are studied employing the local density (LDA) and the self-interaction-corrected (SIC) approximation. Moreover, the X-ray spectra modeling are in good agreement with the electronic and magnetic properties results. [ABSTRACT FROM AUTHOR]

We report on the formation of Tamm plasmon (TP) modes in the visible spectral region at the interface between a Ag film and a ZnSe-based distributed Bragg reflector (DBR). The tuning of the TP eigenenergies within the stop-band in dependence on the DBR top layer thickness is investigated by micro-reflectivity measurements. The experimental findings are compared with calculations using the transfer matrix method. The latter calculations show that strong coupling can be achieved between quantum well (QW) excitons and the TP modes. In addition, the Rabi-splitting energy can be enhanced in a simple TP structure by increasing the number of QWs inside the top layer of the DBR. When a metal layer is deposited on a cold MC sample, micro-reflectivity spectra show a blue shift of the cavity resonance. The TP modes are likewise observed in the same MC sample when reducing the top layer thickness of the DBR. This shift of cavity resonance and formation of TP mode are in good agreement with calculations. These results are rather promising in order to realize a spatial confinement of the polaritons by utilizing metal strips. Such channeling of polaritons opens the way to practical demonstration of exciton-polariton integrated circuits. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

First-principles calculations on the basis of density-functional theory are performed in order to investigate the electronic structures and optical properties of Cr2+:ZnSe with different impurity concentration. Five configurations with the substitution of Zn by one Cr atom in different ZnSe supercells are considered. The results show that the absorption peak intensity and peak width decrease with diminishing Cr2+ concentration and a redshift is observed in the absorption spectra. The experimental observations are in good agreement with the calculated results. An appropriate explanation of the experimental results is presented. [ABSTRACT FROM AUTHOR]

A fast and furnace-free way is reported to synthesize ZnSe from self-sustained combustion reaction between Zn and Se. The synthesized ZnSe shows a zincblende structure and large particle size of > 100 μm, which can be reduced by two magnitude to 1.4 μm by using NaCl as diluent. It is proposed that the added NaCl can lower the reaction temperature and diminish the interfacial area of ZnSe grains by a steric hindrance effect. The ZnSe samples show the characteristic band-edge absorption in visible region, and the band gap energy is estimated to be 2.43–2.58 eV. Under an ultraviolet excitation, the ZnSe samples do not show the near-band-edge blue emission but exhibit strong red emission, which is likely related to the intrinsic point defects in ZnSe. Compared with previous studies, the ZnSe samples synthesized in this work show red emission peaks at even larger wavelength up to 730 nm. [ABSTRACT FROM AUTHOR]

In this work, a one-pot, rapid, green and room temperature photochemical synthesis of transition metal (TM; Cu, Mn)-doped ZnSe nanocrystals (NCs) was reported. NCs were successfully characterized using Fourier transform-infrared (FT-IR), photoluminescence (PL) and UV-Visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), X-ray diffractometry (XRD) and energy dispersive X-ray spectra (EDX). FT-IR spectra confirmed the capping of ZnSe by thioglycolic acid (TGA) molecules. XRD and TEM analysis demonstrated zinc blend phase NCs with an average size of around 3 nm. Band gap of ZnSe NCs was about 3.6 eV which it was decreased by increasing the illumination time. PL spectra of ZnSe NCs showed a broad emission with two peaks located at 380 nm and 490 nm related to excitonic and trap states emission, respectively. For ZnSe:Cu NCs, excitonic emission disappeared completely and PL intensity of trap states emission increased with the increase in the Cu ion concentration so that for precursor ratio of Cu:Zn 1%, optimal value of PL intensity was obtained. For ZnSe:Mn NCs, the excitonic emission decreased gradually with the increase in the impurity concentration whereas trap state emission increased. Moreover, a peak about 590 nm was appeared from 4T1-6A1 transition of the Mn impurity, demonstrating the Mn incorporation inside the ZnSe NCs structure. [ABSTRACT FROM AUTHOR]

Zinc selenide (ZnSe) micro-grasses and microspheres have been successfully grown on graphene oxide sheets by the hydrothermal method. The morphologies, structures, chemical compositions and optical properties of the as-synthesized graphene oxide (GO)/ZnSe microstructures have been characterized by X-ray power diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), ultraviolet-visible (UV–vis) absorption spectroscopy and photoluminescence (PL) spectroscopy. By adjusting the concentration of NaOH and EDTA, needle-like, coral grass-like, orchid-like, and spherical ZnSe microstructures have been synthesized. [ABSTRACT FROM AUTHOR]

ZnSe and ZnS nanocrystals (NCs) were precipitated in glasses through heat-treatment. High resolution transmission electron microscope image confirmed that ZnSe NCs were formed in the silicate glasses, and the X-ray diffraction patterns confirmed that ZnS NCs were precipitated in the borosilicate glasses. Absorption shoulders of the ZnSe NCs and ZnS NCs appeared at ~ 2.76 eV and ~ 3.78 eV, corresponding to the bandgap energies of bulk ZnSe and ZnS crystals, respectively. Instead of the intrinsic emissions, broad-band visible photoluminescence from the surface defects or color centers in the glasses was observed from these ZnSe or ZnS NCs. [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]

Zinc Selenide (ZnSe) thin films of 500 nm thickness were deposited by electron beam evaporation technique and irradiated with 8 MeV electron beam for the doses ranging from 0 Gy to 1 kGy. Optical properties were studied for both irradiated and pristine samples using Ultraviolet-Visible spectrophotometer. The increase in electron dose tends to decrease in transmittance and increase in refractive index of thin film. Irradiated thin film exhibits minimum of 67 % transmittance for 800 Gy with very high absorption of optical energy at 550 nm wavelength. The samples irradiated > 800 Gy tends to redeem the pristine properties. Optical band gap for irradiated thin film were direct and in the range of 2.66 – 2.69 eV. [ABSTRACT FROM AUTHOR]

ZnSe nanoparticles (NPs) with different sizes from 7 to 21 nm were successfully prepared by a solvothermal method in the absence of surfactants. X-ray diffraction, transmission electron microscope, and photoluminescence were used to study the effect of reaction time on the sizes and optical properties of ZnSe NPs. The XRD analysis revealed that all the samples were the cubic zinc-blende structure. The particles size increased from 7 to 21 nm with increasing reaction time. The room-temperature PL spectra showed that the near-band-edge emission peak displayed an abnormal red-shift ranging from 472 to 479 nm when the particle size decreased from 21 to 7 nm, and the intensity of the peak decreased. The photocatalytic activities of the ZnSe NPs of different sizes were also investigated. The ZnSe NPs with smaller particle size had better photocatalytic activities than that with larger particle size for the degradation of Rhodamine B under UV radiation. And the photodegradation of Rhodamine B catalyzed by the ZnSe nanoparticles was a pseudo-first-order reaction. [ABSTRACT FROM AUTHOR]

ZnSe nanocrystals (NCs) were synthesized using a microwave activated method. Synthesized NCs were characterized by means of X-ray diffraction (XRD), UV–visible (UV–vis) optical spectroscopy and photoluminescence (PL). XRD analysis demonstrated cubic zinc blende NCs. TEM image indicated round shape NCs and most of the particles had diameters of about 3 nm. Band gap of the NCs was obtained about 3.15 eV and PL spectra indicates a broad emission with two peaks located about 415 and 500 nm related to band edge and trap state respectively. For ZnSe:Cu NCs, PL intensity of band gap emission of ZnSe NCs at 415 nm decreased gradually with the increase in the concentration of Cu dopant ions and for precursor ratio of Cu:Zn 1% band gap emission at 415 nm disappeared completely. At the same conditions, PL QY was obtained about 2% and 8% for ZnSe and ZnSe:Cu (1%) NCs, respectively. [ABSTRACT FROM AUTHOR]

Novel cactus-like and honeycomb-like ZnSe microspheres have been successfully grown on graphene oxide sheets by hydrothermal method at 190°C for 24h. The morphologies, structures, chemical compositions and optical properties of the as-grown ZnSe microspheres were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), X-ray energy dispersive spectrometer (EDS) and Raman spectra. It was found that the concentration of EDTA was important for the formation of morphologies of ZnSe microspheres. The cactus-like ZnSe microspheres were formed when the concentration of EDTA was 0.3M. With increasing the concentration of EDTA to 0.45M, honeycomb-like ZnSe microspheres were formed. The results of XRD revealed that the as-grown ZnSe microspheres have cubic zinc blende structure. Room temperature photoluminescence (PL) showed that the samples emit blue-green light under ultraviolet light. The results of Raman spectra, XRD and SEM showed that the ZnSe microspheres were grown on graphene oxide sheets. The formation mechanism of ZnSe microspheres grown on graphene oxide sheets was also discussed. [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: The Zinc Selenide (ZnSe) thin films have been deposited on SnO2/glass substrates by a simple and inexpensive chemical bath deposition (CBD). The structural, optical and electrical properties of ZnSe films have been characterized by X-ray diffraction (XRD), Energy Dispersive X-ray Analysis (EDAX), optical absorption spectroscopy, and four point probe techniques, respectively. The films have been subjected to different annealing temperature in Argon (Ar) atmosphere. An increase in annealing temperature does not cause a complete phase transformation whereas it affects the crystallite size, dislocation density and strain. The optical band gap (E g) of the as-deposited film is estimated to be 3.08eV and decreases with increasing annealing temperature down to 2.43eV at 773K. The as-deposited and annealed films show typical semiconducting behaviour, dρ/dT >0. Interestingly, the films annealed at 373K, 473K, and 573K show two distinct temperature dependent regions of electrical resistivity; exponential region at high temperature, linear region at low temperature. The temperature at which the transition takes place from exponential to linear region strongly depends on the annealing temperature. [Copyright &y& Elsevier]

Cubic blende ZnSe nanocrystals (NCs) have been prepared by a low-cost, green, fast, and mass-production route (water bath and hydrothermal conditions using Se and Zn(NO3)2 aqueous solution as the precursors). By changing the hydrothermal temperature and time, we managed to grow ZnSe NCs with diameters varying from 3 nm to 40 nm, among which those of ZnSe NCs with the grain size of 27 nm are more uniform. It is observed that the growth kinetics of ZnSe NCs is influenced strongly by hydrothermal temperature and time, and absorption edge blue-shift occurs as the average size of the NCs changes. The ZnSe NCs growth progress (Ostwald ripening) were observed in the HRTEM image. The room-temperature PL spectrum shows a strong emission band at around 464 nm and also some other deep-level defect emission bands. In addition, the findings point to a valuable role for sufficient NaOH in the preparation of pure ZnSe NCs. [ABSTRACT FROM AUTHOR]

Abstract: ZnSe and ZnS are the prototype II–VI semiconductors and their cubic phase, which occurs naturally as a mineral, has been called the zinc-blende structure. ZnSe has received particular attention as a blue-lasing material and tremendous experimental efforts have been made to fabricate a sustainable ZnSe blue laser. On the other hand, the ternary system is a good candidate for developing optoelectronic devices such as light emitting diodes (LEDs) or semiconductor lasers. It is also used as waveguides and confinement layers in laser diodes (LDs). In the present study, we have computed the electronic and optical properties of ZnSe, ZnS and using the local model pseudopotential method under the VCA. A central aim of this study is to present the electronic and optical properties of the materials of interest in the zinc-blende structure. [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: Molecular beam deposition was used to deposit high quality zinc selenide (ZnSe) thin film on glass substrate at various substrate temperatures and Se/Zn beam equivalent pressure ratios. The best growth condition was identified by analyzing characteristics such as the full width at half-maximum and peak intensity of the (111) preferred orientation in X-ray diffraction patterns. The dependence of lattice constant, growth rate, film composition and optical property on a variety of growth parameters was discussed in detail to identify how the quality of ZnSe film can be improved. [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]

[Display omitted] • Importance of calculation based on the exchange and correlation potential TB-mBJ, revealing the electron distribution DOS in the valence band, the electron transitions in the Brillouin zone and the anisotropy character of ZnSe. • Usefulness of REELS technique, allowing to confirm the calculated electron transitions in the Brillouin zone and to identify the nature of electron states which contribute in the electron transitions from the valence band to the conduction band. • Study of electron states in the band gap of ZnSe with PL spectroscopy. Our work aims to establish a correspondence between the obtained theoretical and experimental results on the electronic and optical properties of ZnSe. The calculated DOS (Density of States) using the FP-LAPW method with the Tran-Blaha modified Becke-Johnson exchange-correlation potential reveal that the upper valence energy levels involve an important contribution from the Se-(4 p and 3 d) electron states with a small contribution from the Zn-2 s states. The real (ε 1 (ω)) and imaginary (ε 2 (ω)) parts of the dielectric function show the anisotropy character of w-ZnSe. The main peaks appearing in the ε 2 (ω) spectrum, are calculated by summing over all contributions of electronic transitions between the pairs of bands V n → C n ′ , where V n is an occupied valence band and C n′ is an unoccupied conduction band. Experimentally, the XPS (X-Ray Photoelectron Spectroscopy) analysis technique is used to show the clean and homogeneous state of ZnSe. To confirm the calculated electron transitions, we use the REELS (Reflected Electron Energy Loss Spectroscopy) technique of great sensitivity for displaying the electron interband transitions. The electron states in the w-ZnSe gap are determined through the Gaussian deconvolution of the photoluminescence spectrum (PLS). [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) structures have the large potential to provide new optico-electrical properties through energy transfer from small-sized QDs to large one. We study the energy transfer process and an influence of ligand on interior states QDs in ZnSe QDs films stabilized by thioglycerol. By combining a steady-state and time resolved photoluminescence spectroscopy measurements we demonstrated the high energy transfer efficiency and its effect on optical properties of random loose-packed QDs arrays. First shown that in ZnSe QDs films the energy transfer time constant can be as fast as 750 ps that is governed by the minimal inter-QDs distance (small length of the thioglycerol molecules) and strong excitons quantum confinement. We discussed also possible causes of an occurrence the so-called blocking QDs in arrays limiting the exciton transport length and energy transfer processes. • We demonstrated the high efficiency of energy transfer and its effect on optical properties of random loose-packed ZnSe QDs arrays. • First shown that the energy transfer time constant can be as fast as 750 ps due to the minimal inter-QDs distance and strong excitons quantum confinement. • Possible causes of an occurrence the so-called blocking QDs in ZnSe QDs films limiting the exciton transport length and the energy transfer processes is discussed. [ABSTRACT FROM AUTHOR]

In this work, two stacked layers of ZnSe thin films are nanosandwiched with aluminum slabs of variable thickness in the range of 10–100 nm. The films which are studied by the X-ray diffraction and ultra-violet visible light spectroscopy techniques exhibit interesting features presented by extension of the cubic lattice parameter, increase in the grain size and reduction in both of the microstrains and defect density. The Al nanosandwiching successfully engineered the energy band gap through narrowing it from 2.84 to 1.85 eV. In addition, the Al nanosandwiching is observed to form interbands that widens upon increasing the Al layer thickness. It also changed the electronic transition nature from direct allowed to direct forbidden type. Moreover, remarkable enhancement in the light absorbability by 796 times is observed near 1.72 eV for two stacked ZnSe layers nanosandwiched with Al slab of thickness of 100 nm. The dielectric constant is also increased three times and the dielectric tunability vary in the range of 3.0-1.2 eV. The nonlinearity in the dielectric spectra and the engineering of the band gap that become more pronounced in the presence of Al slabs make the ZnSe more attractive for nonlinear optical applications. [ABSTRACT FROM AUTHOR]

Hexagonal wurtzite (HWZ) ZnSe nanosheets (NSs) and cubic zinc blende (CZB) ZnSe nanodisks (NDs) are successfully fabricated by treating the relevant precursor ZnSe(en)0.5 (en = ethylenediamine) composites that are prepared by the solvothermal method without or with NaBH4. The morphological and structural analyses show that the NaBH4 affects not only the crystalline phase structure but also the geometrical morphology of ZnSe. The result of nitrogen adsorption–desorption reveals that CZB ZnSe NDs have larger specific surface area than that of HWZ ZnSe NSs. Ultraviolet–visible diffuse reflection spectra (UV–vis DRS) indicate the light‐absorption capacity of CZB ZnSe NDs in the visible region is slightly stronger than that of HWZ ZnSe NSs. The photocatalytic properties of HWZ ZnSe NSs and CZB ZnSe NDs are compared by decolorization of methyl orange (MO) aqueous solution under simulated sunlight illumination. The result shows that the degradation rate constant of MO over CZB ZnSe NDs is ≈1.8 times larger than that of HWZ ZnSe NSs. [ABSTRACT FROM AUTHOR]