ZnS Nanowires Research Articles

MBE-Grown Cubic ZnS Nanowires

Ultrathin ZnS nanowires (NWs) were grown on a sapphire (0001) substrate at 430°C by the molecular-beam epitaxy (MBE) technique using self-assembled Au droplets as the catalyst. It was found that these NWs mainly consist of the cubic phase but a small portion was in the hexagonal phase. The analysis of the temperature-dependent band-edge (BE) emission of these NWs and that of a ZnS thin film revealed that the energy shift of the interband transition on temperature in ZnS is mainly attributed to the electron-phonon interactions. The observed blue shift of the BE emission of ZnS NWs could be quantitatively explained by the confinement of the excited excitons in the NW geometry.

Synthesis, Structure and Growth Mechanism of ZnS Nanowires with High Aspect Ratio

ZnS nanowires were successfully synthesized through the direct reaction of Zn and S vapor via carbon-assisted chemical evaporation deposition method with Au catalyst. The investigations indicated that the size of ZnS nanowires with a diameter of approximately 40 nm was uniform along the axis of the wire and the surfaces were slick. The ZnS nanowire with a hexagonal wurtzite structure was a typical single crystalline structure. HRTEM and SEAD results demonstrated that the nanowire grew along [ ▪100] direction, which was different from the common direction reported in literatures. The growth of nanowires was controlled by vapor-liquid-solid (VLS) mechanism.

Ga‐Doped ZnS Nanowires as Precursors for ZnO/ZnGa2O4 Nanotubes

Ga-doped ZnS nanowires are used as precursors for the preparation of ZnO/ZnGa2O4 composite nanotubes, as shown in the figure. Oxidation of the nanowires induces phase separation resulting in the formation of ZnO/ZnGa2O4 phosphor heterostructures. The nanowires essentially serve as both precursors and templates for the fabrication of the nanotubes.

Mn, Cu Doping and Optical Properties of Highly Crystalline Ultralong ZnS Nanowires

Manganese (Mn) and copper (Cu) doping of ZnS nanowires was achieved by thermal evaporation of Mn, Cu doped ZnS nanopowders. Field emission scanning electron microscopy, and X-ray diffraction studies of the obtained ZnS nanowires demonstrate that the nanowires are single crystal structures and have diameters about 30-200 nm and lengths up to 1 millimeter. Room temperature photoluminescence (PL) measurements show a common PL peak around 520 nm for all ZnS nanowires samples, while impurity-related emission band are observed in doped ZnS nanowires. The dependence of the PL intensity on Mn doping concentration has also been investigated. It is shown that for high Mn doping concentration (10%) in the starting ZnS nanopowders, new emission bands (orange-red and red bands) are observed from the ZnS:Mn nanowires products. The origins of these new emission bands are discussed and brought up for further discussion.

Synthesis of Wurtzite ZnS Nanowire Bundles Using a Solvothermal Technique

Using hydrazine hydrate (N2H4·H2O) as the solvent, bundles of wurtzite ZnS nanowires with diameters of 10−25 nm and lengths about 5−8 μm have been synthesized in high yield via a solvothermal route. The formation process of ZnS nanowire bundles was studied, and it was found that the initially formed N2H4 intercalated zinc sulfide served as the precursor to ZnS. Based on the experimental results, the formation mechanism was discussed. The effect of solvent on the determination and evolution of the morphologies of the resulting nanocrystals was investigated. The optical properties of the as-synthesized wurtzite ZnS nanowire bundles were characterized by UV−vis absorption and PL spectrum.

Fabrication and photoluminescence properties of highly ordered ZnS nanowire arrays embedded in anodic alumina membrane

ZnS nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated from an electrolyte containing ZnCl2 and elemental S in dimethylsulfoxide. Photoluminescence (PL) measurements show a broadband with three peaks centered at about 353, 425, and 520 nm that are attributed to vacancies or interstitial, sulfur vacancy, and point defects respectively.

Controllable growth of electrodeposited single-crystal nanowire arrays: The examples of metal Ni and semiconductor ZnS

We succeeded in controlling the growth direction and microstructure of electrodeposited metal Ni and semiconductor ZnS nanowires in 40-nm diameter alumina pores by tuning the deposition current density. A large current density favors the growth of Ni single-crystal nanowires along the normal direction of the normally high-surface-energy (2 2 0) face, which is attributed to that the large deposition current accelerates the surface adsorption of H ions on the face and therefore lowers its surface energy, whereas a small one is favorable for the growth of wurtzite ZnS single-crystal nanowires along the normal direction of the lowest-surface-energy (1 1 0) face. The present study demonstrates the effect of crystal surface energy on the growth direction of electrodeposited nanowires.

Shape- and Size-controlled Growth of ZnS Nanostructures

A general synthetic method has been developed to precisely control the shape and size of ZnS nanorods, nanowires, whiskers, and hierarchical nanostructures. The control was achieved owing to creation of specific growth conditions while adopting carefully selected catalysts and tuning their size during a catalytic vapor-liquid-solid growth process. The UV-vis absorption spectra of small diameter ZnS nanorods show a blue shift compared with large diameter ZnS nanowires, thus displaying a quantum confinement effect highly valuable for novel nanoscale optoelectronic devices. It is envisaged that it is possible to controllably grow other nanostructures using the analogous approach.

Zinc-blende ZnO and its role in nucleating wurtzite tetrapods and twinned nanowires

In this letter, the authors directly observed the zinc-blende (ZB) ZnO core in the initial formation of wurtzite (WZ) ZnO tetrapods. The formation of the wurtzite (011¯3) twined nanowires is proposed based on the ZB core. Simple bonding density calculation shows that the wurtzite nanowires with {011¯0} side surfaces have the lowest surface energy. A favorable choice of WZ phase over ZB when forming nanostructures is likely to be a result of surface energy minimization. This could be the reason that ZnS nanowires take WZ rather than ZB.

An Empirical Interatomic Potential Approach to Structural Stability of ZnS and ZnSe Nanowires

Structural trends in ZnS and ZnSe nanowires are systematically investigated on the basis of our empirical potential, which incorporates electrostatic energy due to valence-bond and ionic charges. The calculated nanowire cohesive energies for zinc blende, 6H, 4H, and wurtzite structures demonstrate that the stability of crystal structure depends on nanowire diameter. Monte-Carlo calculations to determine the nanowire stacking sequence during nanowire growth also show that nanowires often contain rotational twins, the averaged periodicity of which is almost proportional to nanowire diameter. The periodicity of rotational twins in the nucleation model in which the nucleus consists of facet atoms at the top layer of a nanowire agrees with the observation of rotational twins. The results suggest that our approach is feasible to clarifying structural trends in Zn-based semiconductors nanowires.

Synthesis of Sulfide Nanowire Arrays through Template-Assisted Electrodeposition

Sulfide nanowire arrays have been synthesized by DC electrodeposition from an electrolyte containing S in DMSO. The AAO membrane with the barrier layer has been directly used as template in electrodeposition. The as-synthesized products are characterized by SEM, TEM and resonance Raman spectroscopy. CdS and ZnS nanowires have been obtained, respectively.

High-symmetry ZnS hepta- and tetrapods composed of assembled ZnS nanowire arrays

Sixfold symmetry heptapodlike and threefold symmetry tetrapodlike ZnS structures have been fabricated by thermal evaporation of a ZnS and SiO mixture source in N2 at 1300°C. Both the heptapods and tetrapods have been formed by the self-assembly of ZnS nanowires with the preferred (0001) orientations. Structures and morphologies of the obtained heptapods and tetrapods are thoroughly studied using x-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. Room-temperature photoluminescence spectra taken from the nanostructures show a strong green emission centered at 550nm.

Surface Optic Phonons in Cylindrical and Rectangular Cross-Sectional Semiconducting Nanowires

Raman scattering from surface optic (SO) phonons has been observed and identified in cylindrical and rectangular cross-section nanowires with lateral dimensions in the range 20-50 nm and lengths of ~ 10 microns. The position of the SO band is found to depend on both the shape of the wire cross section (i. e., circular or rectangular) and on the dielectric constant of the external medium. The position of the SO band in GaP and ZnS nanowires is in good agreement with a dielectric continuum model that takes the shape of the wire cross section into account. We propose that the symmetry breaking mechanism which activates the Raman sacttering of the SO phonon in our nanowires is a quasi-periodic modulation of the cross-sectional area along the nanowire axis. We suggest this modulation stems from an interesting growth instability associated with vapor-liquid-solid (VLS) growth.

Microemulsion-mediated solvothermal synthesis of ZnS nanowires

Uniform and high-aspect-ratio ZnS nanowires with length up to several micrometers and diameter of 30–50 nm are synthesized by a facile and low-cost microemulsion-mediated solvothermal method. Moreover, ZnS nanorods and bamboo-leaf-like ZnS nanostructures were also obtained by modulating the reaction parameters. Especially, hollow bamboo-leaf-like ZnS nanostructures formed by radiating those bamboo leaves with electron beam. A reasonable mechanism to the formation of the as-prepared one-dimension zinc blend ZnS nanocrystals is also discussed.

Growth of ultrafine ZnS nanowires

Ultrafine ZnS nanowires have been grown successfully throughthermal evaporation of zinc powder and sulfur powder at 580 and90 °C respectively. The nanowires are mainly in the range of 5–12 nm in diameter, and severalmicrons in length. X-ray diffraction and high-resolution transmission electron microscopeanalysis shows that the ZnS nanowires are of wurtzite structure and have two differentgrowth directions of [001] and []. The growth mechanism is discussed in detail.

ZnS nanowires and their coaxial lateral nanowire heterostructures with BN

ZnS nanowires and their coaxial lateral BN nanowire heterostructures with a length of hundreds of micrometers and an average diameter of ∼300nm were fabricated via one-step chemical vapor deposition method. Wurtzite ZnS nanowires were coated by a shell of fluffylike hexagonal BN sheets distributed randomly. Thermogravimetric analysis indicates that the heterostructures have a much better oxidation resistance compared with ZnS nanowires. Their similar optical property suggests that the ZnS∕BN heterostructures would have potential applications in thermally and chemically rigorous environments.

Heteroepitaxial growth and optical properties of ZnS nanowire arrays on CdS nanoribbons

The authors present the results of heteroepitaxial growth of single-crystalline ZnS nanowire arrays on CdS nanoribbon substrates by the metal-catalyzed vapor-liquid-solid growth method. ZnS nanowire arrays were vertically or crosswise aligned to the surface of CdS nanoribbon substrates. Room-temperature lasing from ZnS nanowire arrays was demonstrated. The present synthesis provides a new approach to the rational design of building blocks for nanodevices.

Field emission and photoluminescence characteristics of ZnS nanowires via vapor phase growth

Large-area ZnS nanowires were synthesized through a vapor phase deposition method. X-ray diffraction and electron microscopy results show that the products are composed of single crystalline ZnS nanowires with a cubic structure. The nanowires have sharp tips and are distributed uniformly on silicon substrates. The diameter of the bases is in the range of 320–530 nm and that of the tips is around 20–30 nm. The strong ultraviolet emission in the photoluminescence spectra also demonstrates that the ZnS nanowires are of high crystalline perfection. Field emission measurements reveal that the ZnS nanowires have a fairly low threshold field, which may be ascribed to their very sharp tips, rough surfaces and high crystal quality. The perfect field emission ability of the ZnS nanowires makes them a promising candidate for the fabrication of flexible cold cathodes.

Synthesis and characterization of shaped ZnS nanocrystals in water in oil microemulsions

Shaped zinc sulfide nanocrystals were synthesized in W/O microemulsions by using cyclohexane/Triton X-100/ n-pentanol/water system. Under different synthetic conditions appearance of two distinct morphologies of ZnS nanocrystals, either cubes or nanowires, was proven by transmission electron microscopy (TEM). The ZnS cubes have an average size of about 25 nm, while the ZnS nanowires have 25 Å diameter and length ranging from several hundred nanometers up to a few microns. The X-ray diffraction analysis (XRD) revealed formation of ZnS with cubic zinc blende crystal structure. Due to two dimensional confinement the exciton of ZnS nanowires is blue shifted compared to the bulk material. Four well-resolved photoluminescence bands in visible spectral region were observed upon excitation of cubic ZnS particles, while in the case of ZnS nanowires emission band was observed at 421 nm. The origin of photoluminescence bands was discussed in details.

Low-temperature synthesis of wurtzite ZnS single-crystal nanowire arrays

The synthesis of highly aligned and ordered wurtzite ZnS single-crystal nanowires at lowtemperatures is crucial for their applications in electronic and optoelectronic nanodevices.In the present study, wurtzite ZnS single-crystal nanowire arrays with a preferred growthalong the [110] direction have been successfully prepared at a low temperature ofT = 120 °C by employing electrochemical deposition techniques using the alumina template with 40 nmdiameter pores. The microstructure of the ZnS nanowires was characterized by x-raydiffraction and transmission electron microscopy studies. A small deposition current isfound to be favourable for the growth of wurtzite ZnS single-crystal nanowires and thecause has been discussed.