ZnSe Nanostructures Research Articles

Dielectric response of poly(vinyl alcohol)–zinc selenide nanocomposite film

Poly(vinyl alcohol)–zinc selenide (PVA–ZnSe) nanocomposite films have been prepared, which offer higher effective permittivity than pure PVA. There is an about 2.5-fold increase (at 420 K) in the effective permittivity at 100 kHz for the 4 wt % ZnSe nanostructure impregnated PVA film as calculated from the dielectric reinforcement function. Prevailing relaxation mechanisms in the nanocomposite films, within the frequency range of 100 Hz ≤ f ≤ 1 MHz and in the temperature range of 298 ≤ T ≤ 420 K, have been discussed on the basis of available theoretical approaches in the literature. AC conductivity behavior reveals that correlated barrier hopping is the ac charge transport mechanism for the nanocomposite films, and the maximum barrier heights vary inversely with the weight percent inclusion of ZnSe nanostructures.

Synthesis, field emission of various ZnSe nanostructures by hydrothermal methods

In this work, grass-like, needle-like and chrysanthemum-like ZnSe nanostructures have been prepared by hydrothermal method at 200°C for 24 h successfully. With different amounts of diethanolamine, various morphologies of ZnSe formed. The structures, morphologies and crystal orientation of as-synthesised ZnSe nanostructures were characterised by X-ray diffractometer (XRD) and scanning electron microscope. The experiment result of XRD indicated that the structures of all as-synthesised ZnSe nanomaterials were cubic crystal. The field emission (FE) properties of as-synthesised samples were tested and the results revealed that the FE properties were influenced by the morphologies significantly. The FE measurement showed that the chrysanthemum-like ZnSe nanostructures had the best FE properties with a high field enhancement factor of 4328 and a low turn-on electric field of 3.4 V μm−1 among all the as-synthesised ZnSe nanostructures. The reaction mechanism of various morphologies ZnSe was also explained as follow.

Synthesis, characterization, and charge transport mechanism of polyaniline/ZnSe nanocomposites for promising optoelectronic applications

The elaboration of organic–inorganic nanohybrid compounds has demonstrated substantial attentiveness owing to an inclusive extent of potential applications in optoelectronic devices. Here, we report about the synthesis of novel hybrid compound based on polyaniline/ZnSe nanocomposites. The ZnSe nanoparticles are prepared by colloidal technique to get average particle size of 8.5 nm. The polyaniline was prepared in the presence of the ZnSe nanostructure. The structure and morphology of the prepared polyaniline/ZnSe nanocomposites were investigated by X‐ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (FTIR). The XRD implied that all patterns are corresponding to the semicrystalline polyaniline and ZnSe with cubic crystal structure. The SEM images revealed that the incorporation of the ZnSe into the polyaniline matrix leads to an increasing of the particles size. The optical features of the polyaniline/ZnSe nanocomposites are investigated by UV–Vis spectroscopy. The optical band gap of polyaniline is decreased from 3.42 to 2.92 eV with increasing the ZnSe content. The electrical conductivity measurement showed that the incorporation of the ZnSe into the polyaniline matrix increased the dc conductivity and decreased the activation energy. The charge transport mechanism belonged to the hopping conduction mechanism. The thermoelectric power measurement depicted that the majority carriers are holes. The mobility and the number of charge carriers are increased, while the potential barrier is decreased with increasing the ZnSe concentration into the polyaniline matrix. POLYM. COMPOS., 39:1724–1730, 2018. © 2016 Society of Plastics Engineers

Aging effect on the structural and optical properties of ZnSe nanostructures

In the present work synthesis of ZnSe nanostructures with different time interval using a simple hydrothermal method has been discussed. The prepared nanostructures were characterized by X-ray diffraction (XRD), diffused reflectance spectroscopy, UV–vis spectroscopy, photoluminescence spectroscopy, Raman spectroscopy and scanning electron microscopy. From the XRD pattern it is observed that the cubic phase of ZnSe nanostructures thus synthesized have increased crystallite size on increasing the time of reaction. The band gap was found to decrease with aging time enhancement for the fabrication of ZnSe nanostructures. A blue shift in the absorption band edge was observed in the synthesized ZnSe nanoparticles as compared to the bulk ZnSe. The absorption intensity also decreased with increased reaction time of the prepared samples.

Formation of ZnSe and ZnS nanostructures from hybrid organic‐inorganic precursors of the type ZnSe(m‐xylylenediamine)1/2 and ZnS(1,3‐diaminopropane)1/2

Two hybrid organic‐inorganic materials, ZnS(1,3‐diaminopropane)1/2 {1} and ZnSe(m‐xylylenediamine)1/2 {2} were used as precursors of nanometric ZnS and ZnSe nanostructures. To obtain a single‐phase semiconductor, refluxing in different solvents (acetonitrile, 1‐octanol, 1,6‐hexanediol) with various boiling points was applied. In this method, the synergic effect between temperature and the properties of the reactant medium was used to remove amines from hybrid material containing semiconducting slabs and to form pure nanometer‐sized semiconducting grains whose properties were different than those of the corresponding bulk phases. The main goal of our research was to answer the question whether reaction conditions have an impact on the features of obtained semiconducting grains of ZnS and ZnSe. Accordingly, all obtained samples were analyzed using the powder diffraction method, UV‐vis spectroscopy and scanning electron microscopy.

Synthesis, field emission and optical properties of ZnSe nanobelts, nanorods and nanocones by hydrothermal method

ZnSe nanostructures, such as nanobelts, nanorods and nanocones, were successfully synthesized on Zn foils via a hydrothermal method using EDTA as soft template at low temperature. EDTA played a significant role on the morphology of ZnSe nanomaterials. X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS) were carried out to characterize the microstructures and chemical compositions of the as-synthesized ZnSe samples. XRD patterns indicated that the as-synthesized ZnSe samples belonged to a cubic zinc blende structure. SEM observation obviously showed that the nanocones had very sharp tips compared to nanorods and nanobelts. The field emission (FE) measurement showed that the as-synthesized ZnSe nanocones had a lower turn-on field of ~1.6Vμm−1 at the current density of 10μAcm−2. A high field enhancement factor of ~4514 was achieved for the ZnSe nanocones. The superior field emission properties were probably attributed to the sharp tips of the ZnSe nanocones. Room temperature photoluminescence (PL) spectroscopy of the ZnSe nanostructures showed a wide band emission from blue light to orange light. The as-prepared ZnSe nanomaterials have promising applications in optoelectronic devices. A possible formation mechanism of ZnSe nanobelts, nanorods and nanocones was also proposed and discussed.

Effect of Ag doping on structural and optical properties of ZnSe nanophosphors

In the present study undoped ZnSe and silver doped ZnSe viz. Zn1−xAgxSe (x=1%, 3%, 5%) nanophosphors are synthesized via a simple hydrothermal route. The prepared nanophosphors were characterized by X-ray diffraction (XRD), UV–vis spectroscopy, Photoluminescence (PL) spectroscopy, Raman spectroscopy and field emission scanning electron microscopy (FE-SEM). XRD patterns of samples reveal the formation of cubic phase for the undoped ZnSe, 1% and 3% Ag doped ZnSe, and 5% silver doped sample indicates the formation of another phase of Ag2Se along with the original one. The crystallite size is found to increase from 4.2nm to 13.5nm for Ag doped ZnSe nanostructures. Some nanorods structures are formed in Zn0.95Ag0.05Se as confirmed by the FE-SEM images. The UV–vis analysis shows a blue-shift of the absorption edge of the undoped ZnSe and Ag doped ZnSe nanophosphors as compared to its value for bulk ZnSe. The gradual decrease in PL intensity with increased amount of Ag doping in the host ZnSe nanophosphors is explained on the basis of concentration quenching mechanism.

Synthesis of p-type phosphorus doped ZnSe nanowires and their applications in nanodevices

High-quality phosphorus (P) doped ZnSe nanowires (NWs) were synthesized through a chemical vapor deposition (CVD) method. The p-type conductivity of P-doped ZnSe NWs was confirmed by field-effect transistors (FETs), which show the hole mobility (μh) of 0.173cm2V−1s−1 and carrier concentration (nh) of 5.5×1019cm−3, representing the highest value achieved for p-type ZnSe nanostructures thus far. High-performance photodetectors (PDs) were fabricated by construction of ZnSe/Si p-n heterojunction diodes, which show high responsivity (R) of 1.1×105A/W and photoconductivity gain (G) of 2.9×105 at forward bias and fast response speed of 74/153μs at reverse bias to the incident light. These results reveal that such P-doped ZnSe NWs are excellent candidates for optoelectronic applications.

Shape, size and configuration tuning in ZnSe nanostructure thin films through deposition temperature, pH controlling and deposition time

We investigate the deposition temperature, pH and deposition time that govern evolution of the nanoparticle shape, size and density of ZnSe nanoparticle arrays. The nanoparticle arrays were grown on glass substrate using a facile chemical bath deposition method. The samples were also characterized by absorbance spectra for energy band gap determination and scanning electron microscopy. In comparison to other similar works, our method is simple, low cost and can be easily controlled. We find that temperature helps to tailoring the nanoparticle shape and has a critical role in comparison with other parameters such as pH and deposition time.

Synthesis of Er and Yb-doped cubic and hexagonal phase ZnSe nano-assembled microspheres and their photocatalytic activities

We O2− synthesized ZnSe as well as Er and Yb-doped ZnSe nano-assembled microspheres by a hydrothermal method with and without hydrazine. ZnSe microspheres with a cubic phase were obtained with hydrazine, while ZnSe microspheres showed mixed cubic and hexagonal phases when hydrazine was not used. Introduction of low levels of Yb and Er resulted in morphologies of plates and rods, respectively, and these morphologies were unchanged when higher doping concentrations were used. The synthesized ZnSe was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction crystallography, thermogravimetric analysis, UV–visible absorption, and photoluminescence spectroscopy. Photodegradation of methyl orange by undoped, Er and Yb-doped ZnSe was tested under visible light. Photoluminescence spectroscopy using terephthalic acid confirmed that OH radicals were efficiently formed over the doped ZnSe nanostructures upon visible light irradiation.

Synthesis of grass-like ZnSe nanostructures on graphene oxide and their excellent field emission properties

Setaria palmifolia-like, turfgrass-like and needle-like zinc selenide (ZnSe) nanograsses have been successfully grown on graphene oxide sheets (GOss) by a hydrothermal method. The morphologies and compositions of as-synthesized graphene oxide (GO)/ZnSe nanograsses have been characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM). The morphologies of ZnSe nanograsses on GOss were highly manipulated by adjusting the addition amount of diethanolamine. The field emission (FE) properties of graphene oxide (GO)/ZnSe nanograsses were measured and found to be strongly influenced by the morphologies of ZnSe. The results show that GO/ZnSe nanograsses composed of nanorods have best FE properties with a low turn-on electric field of 4.5Vμm−1 and a high field enhancement factor of 2715 among all the samples.

Microphotoluminescence of individual ZnSe nanoribbons

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.

Efficient Superionic Conductor Catalyst for Solid in Solution-Solid-Solid Growth of Heteronanowires.

How efficient could a superionic conductor catalyst be? Beyond the traditionally used molecular precursors when the solution dispersed solid nanomaterials of variable size, shape and phase are introduced under certain reaction condition; the catalyst is found to digest all these structures in minutes irrespective of their phase and morphology, resulting unique heteronanowires. This has been inspected here by employing different ZnSe nanostructures as precursor for Ag2Se nanocrystal catalyst in its superionic conductor phase to obtain the Ag2Se-ZnSe heteronanowires. This dissolution and formation process of these nanostructures is correlated with the change in the reaction temperature profile, the phase of the catalyst, the shape/phase and surface ligands of the source nanostructures, and the possible mechanism of the unique heteronanowires growth has been investigated.

Synthesis of ZnSe Quantum Dots with Stoichiometric Ratio Difference and Study of its Optoelectronic Property

ZnSe quantum dots are key research interest of many groups from past few decades because of their novel opto-electronic properties. It is a direct wide band gap semiconductor having a band gap of 2.70eV. ZnSe based quantum dots have many application in various fields such as solar cell, scintillators, schottky diodes etc. Considering its multifarious applications and asserts of ZnSe nanostructures, it is a worldwide research interest. In this study we are going to report a conventional wet chemical method to synthesize ZnSe quantum dots with stoichiometric ratio difference of 3:2, 3:1 and 1:1 between Zn and Se. Characterization method such as Photoluminescence, X-Ray Diffraction (X.R.D), Transmission Electron Microscopy (T.E.M) were carried out. TEM imaging was executed to find out the size distribution, which was in the range of 2 to 10nm (diameter). A wurtzite crystal structure of quantum dots has been confirmed by X.R.D also a band edge emission with a distinct blue shift in terms of wavelength is observed from Photoluminescence studies.

Au–Thiol Interaction Chemistry to Influence the Structural Transformation of Semiconductor Nanocrystals and Formation of Giant Nanostructures

Giant nanostructures which are difficult to design by the classical growth process can be fabricated in a facilitated and well programmed surface ligand removal protocol employing the thiol-gold strong interaction chemistry. When thiol capped small ZnSe seed nanocrystals are treated with amine capped gold particles, gold snatches the thiol ligands from ZnSe and forces them to agglomerate leading to the giant crystalline ZnSe nanostructures.

Synthesis and photoluminescence properties of wash-board belt-like ZnSe nanostructures

Washboard belt-like zinc selenide (ZnSe) nanostructures are successfully prepared by a simple chemical vapor deposition (CVD) technology without catalyst. The phase compositions, morphologies and optical properties of the nanostructures are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) spectroscop, respectively. A vapor-liquid mechanism is proposed for the formation of ZnSe belt-like structures. Strong PL from the ZnSe nanostructure can be tuned from 462 nm to 440 nm with temperature varying from 1000 °C to 1200 °C, and it is demonstrated that the washboard belt-like ZnSe nanostructures have potential applications in optical and sensory nanotechnology. This method is expected to be applied to the synthesis of other II–VI groups or other group’s semiconducting materials.

Fabrication of one-dimension ZnSe and ZnO nanostructures via anodic alumina template assisted vapor–liquid–solid growth process

One-dimension ZnSe and ZnO nanostructures with controlled diameters from 10 to 80nm and lengths from 30nm to micrometers were grown via the vapor–liquid–solid growth process using Au nanoparticles as catalysts fabricated by anodic aluminum oxide template assisted vapor deposition. The dependence of the growth on Au nanoparticle (NP) diameters and vapor stoichiometry during growth was investigated. Statistical analysis of the dimensions of nanostructures showed that large Au NPs led to thick and long nanorods (NRs) or nanowires (NWs) within the initial growth phase, but resulted in a slow growth rate as the NRs elongate. The diameter ratio of NRs to Au NPs, or R (Dnanorod/DAu), decreases from 0.45 to 0.32 as the mean length of NRs increases from 30nm to 230nm. The composition changes as the NRs elongate, as identified by energy dispersive X-ray analysis, indicate that the stoichiometry of ZnSe NWs can be controlled from Zn-rich to Se-rich; however, for ZnO NRs and NWs, their stoichiometry maintains Zn-rich throughout the growth process. These results are significant for the controlled fabrication of one-dimension nanostructures since their optoelectronic properties are directly determined by their dimensions and composition stoichiometry.

Luminescence and local photonic confinement of single ZnSe:Mn nanostructure and the shape dependent lasing behavior

One-dimensional Mn–ZnSe nanostructures with high crystallite quality were synthesized by the CVD method. Transmission electron microscopy was used to study the defect state, crystal lattice and growth direction of as-prepared nanostructures. Raman spectra under varied excitation wavelengths confirmed the dopant modes of Mn(II) and the inhomogeneity. The micro-photoluminescence (PL) spectra of individual nanostructures under CW laser excitation with different powers showed the dominant trapped state emission with periodic multi-peaks. The selected peak mapping indicated that there were many integrated Fabry–Perot cavities and whispering gallery mode cavities within the nanowires/nanoneedles and nanobelts, respectively, which can be accounted for by inhomogeneous optical phases in the Mn–ZnSe nanostructure. The phase may be introduced by both Mn doping and structural relaxation. The micro-PL spectra under nanosecond pulse laser excitation produce low threshold lasing lines near the band edge of Mn–ZnSe nanostructures. The lasing occurs due to the dominant interaction between bound excitons at high density, evidenced by its appearance close to the LO phonon replica. The belts show much stronger lasing emission due to larger 2D coherent space than the wires due to the inhomogeneity induced by the doping process. The different optical behavior with changing excitation pulses may find applications in future photonic devices of II–VI nanostructures.

Tuning the p-type conductivity of ZnSe nanowiresvia silver doping for rectifying and photovoltaic device applications

Applications of one-dimensional (1D) semiconductor nanostructures in nanoelectronics and nano-optoelectronics rely on the ability to rationally tune their electrical transport properties. Here we report the synthesis of single-crystalline Ag-doped ZnSe nanowires (NWs) by using silver sulfide (Ag2S) as the p-type dopant via a thermal evaporation method. The ZnSe:Ag NWs had the zinc blende structure with [11 ] growth orientation. Significantly, the conductivities of the NWs could be tuned over 9 orders of magnitude by adjusting the Ag doping levels. Field-effect transistors (FETs) constructed from the ZnSe:Ag NWs verified their p-type nature with a hole concentration of up to 2.1 × 1019 cm−3, which is the highest value achieved for p-type ZnSe nanostructures thus far. Schottky barrier diodes (SBDs) based on the ZnSe:Ag NW/ITO junctions exhibited remarkable rectifying behavior, with a rectification ratio of >107 and a small ideality factor of ∼1.29 at 320 K. Moreover, photovoltaic devices were fabricated from the ZnSe NW array/Si p–n heterojunctions by aligning the p-ZnSe NWs in a parallel fashion on a n-Si substrate. The device with a graphene top electrode showed a large fill factor (FF) of 61%, yielding a power conversion efficiency of ∼1.04%. The realization of p-type ZnSe NWs with tunable conductivity opens up opportunities for a host of high-performance nanoelectronic and nano-optoelectronic devices.

Chlorine‐Doped ZnSe Nanoribbons with Tunable n‐Type Conductivity as High‐Gain and Flexible Blue/UV Photodetectors

AbstractAlthough significant progress has been achieved in the fabrication of ZnSe nanostructures with various structures and morphologies, it remains a major challenge to rationally tune their transport properties for applications in future nano‐optoelectronic devices. The synthesis of chlorine‐doped ZnSe nanoribbons (NRs) with tunable n‐type conductivity is achieved by a thermal co‐evaporation method. The ZnSe:Cl NRs have single‐crystal wurtzite structure and [120] orientation, which also show high crystalline quality and structural integrity comparable with the undoped NRs. Electrical measurements on a single ZnSe:Cl NR reveal a substantial enhancement of the conductivity upon Cl doping. The conductivity could be further tuned by adjusting the doping level. In addition, highly sensitive blue/UV photodetectors are constructed based on the ZnSe:Cl NRs. The devices exhibit an extremely high gain of approximately 106, and the UV response could be enhanced through a fast annealing process in air. By replacing the rigid SiO2/Si substrate with a PET substrate, flexible ZnSe:Cl NR photodetectors with excellent stability and durability under strain are realized. It is expected that the ZnSe:Cl NRs with tunable n‐type conductivity will have important applications in the new generation nano‐optoelectronic devices.