Growth Of ZnS Research Articles

Influence of organozinc ligand design on growth and material properties of ZnS and ZnO deposited by atomic layer deposition

Deposition of ZnS and ZnO by the atomic layer deposition technique is performed using both dimethylzinc (DMZn) and diethylzinc (DEZn) as the metal source and H2S or H2O as the counter-reactant. The deposited films are characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy, and ultraviolet-visible measurements, and particular emphasis is placed on the influence of the metal precursor on material growth and properties. The use of DMZn as the Zn source results in faster material deposition than growth with DEZn due to a less significant steric factor with DMZn. The material properties of the deposited ZnS films are nearly identical for the DMZn/H2S and DEZn/H2S processes, whereas XRD provided evidence for slight variations in the material properties of the DMZn/H2O and DEZn/H2O grown films. Overall, pure and crystalline ZnS and ZnO films can be deposited via either DMZn or DEZn, and ZnO growth is more affected by the modification of the ligand of the Zn precursor from methyl to ethyl.

Ultralong zinc-blende ZnS nanowires grown on polar C face of 6H–SiC substrates at low temperatures by metalorganic chemical vapor deposition

Abstract Ultralong ZnS nanowires with high purity were grown on Au-coated polar C face of 6H–SiC substrates via metalorganic chemical vapor deposition at low temperatures. The ZnS nanowires have zinc-blende structure and the length is up to tens of micrometers. HRTEM investigations show that the nanowires are well crystalline single crystal grown along [1 1 1] and free of bulk defects. However, sparse straight and curved nanowires with poor crystalline nature are randomly grown on the Au-coated Si face of 6H–SiC substrates. We deduce that the growth of ZnS is related to the substrates and C face can enhance Au-catalytic VLS growth. The CL spectra of an individual nanowire grown on C and Si face reveal different optical properties. Intrinsic sulfur and zinc vacancies are the main reasons for the 458.1 nm and 459.2 nm blue emission detected in the nanowire grown on C face and Si face, respectively. Nevertheless, an unusual green emission at 565.1 nm is observed in the poor crystalline nanowire grown on Si face, which originates from the bulk defects.

Fabrication of Ordered Nanostructures of Sulfide Nanocrystal Assemblies over Self-Assembled Genetically Engineered P22 Coat Protein

Ordered ZnS and CdS nanocrystal assemblies have been synthesized by a facile bioinspired approach consisting of an initial self-assembly of engineered proteins into spherical biotemplates and a subsequent protein-directed nucleation and growth of ZnS and CdS nanocrystals symmetrically distributed over the self-assembled biotemplates.

The synthesis and photocatalytic properties of epitaxial SnO 2–ZnS nanocomb heterostructure

A growth of SnO 2–ZnS heterostructure was realized by a rational two-step thermal evaporation method. Starting with Sn powder, the SnO 2 bicrystalline nanoribbons were grown on the silicon wafers. The secondary growth of ZnS on the former SnO 2 nanostructures correspondingly resulted in the SnO 2–ZnS nanocomb structures. We investigated the morphology, detailed structure by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). It revealed that the ZnS nanobranches with [001] growth direction are epitaxial grown from the (− 101) crystal plane of the SnO 2 trunks with a good lattice match. The nanocomb exhibited an effective photocatalytic activity.

Structural Evolution and Photoluminescence of Zinc-Blende CdSe-Based CdSe/ZnS Nanocrystals

Anisotropic heterostructures are of significant importance in creating novel nanomaterials and realizing their application potentials. Here we report a study on structural evolution and photoluminescence of zinc-blende CdSe-based CdSe/ZnS core/shell nanocrystals with variations of the ZnS shell growth. When raising the shell growth temperature, the structure of CdSe/ZnS can be tuned from sphere to near triangle, and to branched ones, including a tetrapod-like structure. But fast interface diffusion and alloying at high growth temperature will corrupt the branched structure and induce a blue shift in the luminescence spectrum. For tetrapod-like CdSe/ZnS nanocrystals, the growth of ZnS exhibits a pattern of first elongating and then branching, which is accompanied by rising, steady, and descending phases of the photoluminescence quantum yield. This study shows the shape tuning and interface alloying of CdSe/ZnS nanocrystals, and reveals that a moderate growth temperature is necessary for obtaining tetrapod-like CdSe/ZnS nanocrystals.

ZnS:N and ZnS:N,Ag grown by molecular beam epitaxy

AbstractThe N‐doping conditions have been investigated in the growth of ZnS:N by molecular beam epitaxy using RF plasma of N2 gas. As a result, high growth temperatures are found to be suitable for the effective incorporation and the activation of N acceptors. The capacitance versus voltage data of the ZnS:N layers grown at around 350 °C exhibit p‐type behavior, while the undoped layers show an n‐type characteristic due to residual donors. ZnS:N,Ag epitaxial layers were also grown to investigate the effect of Ag‐co‐doping. It is shown that the p‐type behavior of the N‐doped layers is enhanced by the Ag‐co‐doping. This suggests the formation of Ag‐related complex centers compensating residual donors (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis and self-assembly of Cu1.94S–ZnS heterostructured nanorods

Cu1.94S–ZnS heterostructured nanorods are prepared by injecting Zn(acac)2-dodecanethiol solution into hot reaction systems containing Cu1.94S nanocrystals which catalyze the pyrolysis of Zn(acac)2 and the following epitaxial growth of ZnS on Cu1.94S seeds. Crystallographic analysis suggests that the built-in p–n type heterostructures allow the dipole moment vectors of both the Cu1.94S “head” and ZnS “tail” to overlap, consequently giving rise to unexpected zipper-like self-assembled structures formed by the heterostructured Cu1.94S–ZnS nanorods.

The two-step thermochemical growth of ZnS:Mn nanocrystals and a study of luminescenceevolution

In this work we report a new thermochemical method for the synthesis of ZnS:Mn nanocrystals.Zn(NO3)2 andNa2S2O3 were used as the precursorsand Mn(NO3)2 was the source ofimpurity. Thioglycerol (TG,C3H8O2S) was also used as the capping agent and the catalyst of the reaction.Na2S2O3 is a heat sensitive material which releases S species upon heating. Consequently,the reaction proceeds in temperatures higher than room temperature. Thereaction was done in two steps. In the first step, the precursors were heated at96 °C for an hour without TG. In the second step, TG was injected to the solution and theheating process was continued for longer heating durations. A fast growth occurredin the first 10 min after the addition of TG, resulting in a sample with a bandedge located at 4.0 eV. The growth was followed by elimination of the sample’sscattering and emergence and increase of the luminescence during the heating process.Transmission electron microscopy and x-ray diffraction analyses demonstrated roundshaped cubic phase ZnS:Mn nanocrystals with an average size around 3.0 nm. Theluminescence emerged from about 15 min after the addition of TG. The emissionwas located at around 585 nm, demonstrating the Mn incorporation inside theparticles. The luminescence intensity increased with time and saturated during thesecond step of the heating process. Finally, we propose a model explaining theformation and changes in the scattering and luminescence characteristic of theZnS:Mn nanoparticles. The model is based on the separation of the nucleation andgrowth steps of the synthesis in the first and second steps of the reaction. Thisseparation directly affects the achievement of the luminescent ZnS:Mn nanocrystals.

ZnS xSe 1−x nanowire arrays with tunable optical properties grown on ZnS nanoribbon substrates

Heteroepitaxial growth of single-crystalline ZnS x Se 1− x nanowire arrays on ZnS nanoribbon substrates by the metal-catalyzed vapor–liquid–solid growth method is reported in this work. ZnS x Se 1− x nanowire arrays were grown, crosswise aligned on the top surface and vertically aligned on the side surfaces of the ZnS nanoribbon substrates, with variable composition and tunable optical properties. Room-temperature lasings of the nanowires with different compositions of x∼0.85, 0.76 and 0.45, showing lasing modes due to the formation of optical waveguides and resonance cavities, were located at ∼367, 378 and 421 nm, respectively. Low-temperature photoluminescence measurements were also carried out to study the optical properties of the heteroepitaxial nanostructures. The present work provides a new approach, which can lead to the rational design of building blocks for the construction of nano-devices.

Growth of ZnS nano-crystallites in gel and their characterization

The conditions for the gel growth of ZnS were studied in this paper. The controlled reaction between the CH 3CSNH 2 and Zn(NO 3)·6H 2O solutions by the diffusion process in a metasilicate gel was used for growing ZnS crystals. The nano-crystallites formed in the gel have been examined by electron microscopy. The following results were obtained: (1) the resulting particles with a size of 5 nm were identified to be zinc-blende ZnS particles and (2) the luminescence property of the crystals was studied by means of cathode luminescence spectroscopy.

Mechanism of Properties of Noble ZnS–SiO2 Protection Layer for Phase Change Optical Disk Media

A ZnS–SiO2 composite dielectric is widely used in the optical stack designs of rewritable optical recording media as an index-matching medium and as a protection layer for the high-index chalcogenide (compound with sixth group element of S, Se, Te) phase change material used in these media. The addition of Si and O to ZnS is primarily intended to stabilize against crystalline grain growth of ZnS with high numbers of direct overwriting cycles. In this study, we carry out infrared (IR) spectroscopy to clarify the role of Si in this stabilization process. IR spectroscopy is performed on sputter as-deposited and annealed ZnS–SiO2 dielectric protection layers. We find that Si exists not in the SiO2 oxide phase but as [SiS4-nOn] tetrahedrons. Moreover, zinc and sulfur do not exist as ZnS, but in highly chemically disordered ZnS:O crystallites. The highly directional and rigid covalent bonds in the [SiS4-nOn] tetrahedrons are key to establishing thermal stability against the coalescence of ZnS. The importance of the Si–S bond also extends into a more thorough understanding of the low thermal conductivity of the ZnS–SiO2 material. The consideration of elastic implications allows us to predict an average phonon velocity less than 50% compared to that in SiO2. With this, we predict a thermal conductivity of 0.0067 W cm-1 K-1 for this material, which is in complete agreement with measured values.

Aging of electroluminescent ZnS:Mn thin films deposited by atomic layer deposition processes

Electroluminescent ZnS:Mn thin films were deposited by the atomic layer deposition (ALD) technique. The deposition processes were based on ZnI2 or ZnCl2 as the Zn source and Mn(thd)3 (thd=2,2,6,6-tetramethyl-3,5-heptanedionato) as the Mn source. The ZnI2 process was found to have a wide temperature range between 300 and 490°C where the growth rate was independent of the deposition temperature, which offers the possibility to select the deposition temperature according to the thermal stability of the dopant precursor without reducing growth of ZnS. The electro-optical measurements suggested that the amount of space charge was lower within the phosphors made with the iodide process, which resulted in higher efficiency of the “iodide” devices as compared to the “chloride” devices. Brightness and efficiency of the best iodide device after 64h aging were 378cd∕m2 and 2.7lm∕W, respectively, measured at 60Hz and at 40V above threshold voltage. Conversely, brightness and efficiency of the best chloride device after 64h aging were 355cd∕m2 and 1.6lm∕W, respectively. On the other hand, changes in the emission threshold voltages indicated that the chloride devices aged slower than the iodide devices. Though the samples were annealed later at high temperature, the deposition temperature was found to be a significant parameter affecting the grain size, luminance, and efficiency of the devices. Overall, the results of this study show that a relatively small change in the Zn precursor can have a clear impact on the electro-optical properties of the devices, and that a mixed halide/metalorganic ALD process can produce an electroluminescent device that ages relatively slowly.

Crystal growth of electroluminescent ZnS:Cu,Cl phosphor and its TiO 2 coating by sol–gel method for thick-film EL device

Bigger-sized spherical particle of ZnS:Cu,Cl to be employed for electroluminescent (EL) device has been synthesized using a new eutectic mixture as flux. The best composition of the flux was the mixture of BaCl 2·2H 2O, MgCl 2·6H 2O and NaCl in the mole percentage ratio of 13.8:39.9:46.2 and when the total amount of the mixture was 6% of the total weight of ZnS. The phosphor was synthesized firing at higher temperatures in two steps. First step firing at 1150 °C gave the hexagonal phase of the ZnS phosphor particles. Low intensity ball-milling of the phosphor pastes in solvents converted hexagonal phase partially to the cubic phase of the phosphor, which is an essential step. Mixing with copper sulfate or copper(I) halides and magnesium chloride and then firing (second step) at 750 °C gave a phosphor with better luminescent characteristics and converting to almost 100% cubic phase. The phosphor particles having size >0.020 mm size were sieved and coated with TiO 2 made by sol–gel process using titanium(IV)-isopropoxide as a precursor. The phosphor particles were coated twice with the TiO 2 sol and finally calcined at 400 °C in nitrogen atmosphere. The EL devices were fabricated with the synthesized phosphor using a screen-printing method.

One-Step Preparation of Coaxial CdS-ZnS and Cd1-xZnxS-ZnS Nanowires

Preparation of coaxial (core–shell) CdS–ZnS and Cd1–xZnxS–ZnS nanowires has been achieved via a one-step metal–organic chemical vapor deposition (MOCVD) process with co-fed single-source precursors of CdS and ZnS. Single-source precursors of CdS and ZnS of sufficient reactivity difference were prepared and paired up to form coaxial nanostructures in a one-step process. The sequential growth of ZnS on CdS nanowires was also conducted to demonstrate the necessity and advantages of the precursor co-feeding practice for the formation of well-defined coaxial nanostructures. The coaxial nanostructure was characterized and confirmed by high-resolution transmission electron microscopy and corresponding energy dispersive X-ray spectrometry analyses. The photoluminescence efficiencies of the resulting coaxial CdS–ZnS and Cd1–xZnxS–ZnS nanowires were significantly enhanced compared to those of the plain CdS and plain Cd1–xZnxS nanowires, respectively, owing to the effective passivation of the surface electronic states of the core materials by the ZnS shell.

Effects of 2D SiO2 Nanorod-Modified Substrates on the Morphology and CL Properties of ZnS:Mn Particle-like Thin-Film Phosphors

To improve light extraction from ZnS:Mn thin-film phosphors, we have studied the effects of introducing various two-dimensional (2D) nanorod arrays onto glass substrates. We determined the effects of 2D nanorods on the morphology and cathodoluminescence (CL) emissions of ZnS:Mn thin films with a view to optimizing the lattice constant of the array and the diameters of the nanorods. Particle-like thin-film phosphors were obtained from the sputtering growth of ZnS:Mn thin films on the nanorod-modified glass substrates, particularly for nanorods with higher aspect ratios and lower nanorod array density. We obtained a significant enhancement (a factor of ) of the CL extraction efficiency at the interface between ZnS and air, for low voltage electron beam excitation of ZnS:Mn thin-film phosphors deposited on 2D nanorod-modified substrates. This improvement in the extraction efficiency is due to the uniform and nanoscale particle-like morphology of these thin-film phosphors, as well as to the diffraction scattering produced by the 2D periodic nanorod array.

Simulation of the Embryonic Stage of ZnS Formation from Aqueous Solution

We investigate the processes of cluster formation and growth of ZnS from aqueous solution using molecular dynamics simulation techniques. The influence of both temperature and concentration is studied. We show that, at lower temperatures, the crucial process is the transformation of an outer-sphere Zn/S complex to an inner-sphere ion pair. Further growth of the latter is fast to generate negatively charged planar clusters. These clusters interact to form more stable, closed structures, which are found to be the global minima configurations in vacuo. At higher temperatures, no outer-sphere ion pairs are formed, and the larger cluster configurations form much more quickly.

Controlled growth of ZnS:Mn nanophosphor in porous silica matrix

The development of nanophosphors of desired sizes and properties for various practical applications and its growth in quantitative amounts inside the pores of an inorganic matrix is presented. By doing so, nanophosphors get surface passivated and are stabilized against environmental attacks. Accordingly, in the present study, the growth parameters for ZnS:Mn nanophosphors were systematically studied inside a SiO2 gel matrix, which can act as a capping agent as well. The samples were prepared using the sol-gel technique, followed by annealing at different temperatures to remove the trapped fluid inside the amorphous silica cage. Two categories of samples with lower (3.11×10−4) and higher (1.5×10−1) ZnS∕SiO2 molar ratios were studied. The x-ray diffraction and scanning electron microscopy observations show that upon annealing, the nanocrystals grow in size and undergo a phase transition from cubic to hexagonal at temperatures between 700 and 900°C. This is one of the very few known reports published on nano hexagonal ZnS formation. The observed phase transition is possibly the combined effect of the high-temperature (∼900°C) and annealing-related compressive stress induced on the nano-ZnS by the silica cage. There has been formation of an intermediate metastable phase of the zinc silicate at annealing temperatures around 700°C. The particle size distribution and emission properties were correlated using the optical absorption and photoluminescence (PL) results. The unannealed cubic nano-ZnS:Mn samples gave a broad PL, peaking at ∼585nm, whereas the samples annealed at 900°C for 5h gave a narrow and sharp PL at ∼590nm. This is attributed to the more efficient T14→A16 transitions of Mn in the resultant hexagonal nano-ZnS matrix.

Microemulsion-mediated synthesis of cadmium zinc sulfide nanocrystals with composition-modulated optical properties

Cadmium zinc sulfide nanocrystals were synthesized by a microemulsion-mediated process, which involving two steps: the preparation of CdS (or ZnS) seeds and the succedent hydrothermal growth of ZnS (or CdS) component. The XRD results show that the cadmium zinc sulfide nanocrystals with CdS seeds present a hexagonally homogeneous alloyed structure, while the ones with ZnS seeds mainly take on the characteristic of hexagonal CdS nanocrystals. The intrinsic factors influencing the crystal structures were discussed. The UV–vis and photoluminescence (PL) spectra indicate that the optical properties of the obtained nanocrystals with CdS seeds can be continuously modulated by tuning their compositions, although their sizes and size distributions are not under a strict control. The composition-modulated strategy, along with the hydrothermal microemulsion process, will be an effective route to achieve semiconductor nanocrystals with tunable optical properties under more manageable conditions.

25pB11 Epitaxial growth of ZnS on Si(100) by two-source vacuum evaporation method(NCCG-34)

25pB11 Epitaxial growth of ZnS on Si(100) by two-source vacuum evaporation method(NCCG-34)

Optical Properties and Structure Analyses of Zinc SulfideNanorods

ZnS nanorods were synthesized using solvothermal process withethylenediamine as a bidentate ligand to form Zn2+ complexes anddodecylthiol providing an effective control over the crystal growth ofZnS nanorod. The microstructure of the nanorods was characterized byx-ray diffraction and transmission-electron microscopy. The opticalproperties of ZnS nanorods were examined by the photoluminescencespectrum.