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The physical properties of Zn(1-x)Mn(x)O nanoparticles synthesized by thermal decomposition are extensively investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman light scattering and Hysteresis measurements. XRD and XPS spectra reveal the absence of secondary phase in nanocrystalline ZnO doped with 5% or less Mn; and, later confirms that the valance state of Mn to be 2+ for all the samples. Raman spectra exhibit a peak at 660 cm(-1) which we attribute to the intrinsic lattice defects of ZnO with increasing Mn concentration. Overall, our results demonstrate that ferromagnetic properties can be realized while Mn-doped ZnO obtained in the nanocrystalline form.

A simple Ar(+)-ion irradiation route has been developed to prepare gold nanoneedle arrays on glass substrates for surface-enhanced Raman scattering (SERS)-active substrates. The nanoneedles exhibited very sharp tips with an apex diameter of 20 nm. These arrays were evaluated as potential SERS substrates using malachite green molecules and exhibited a SERS enhancement factor of greater than 10(8), which is attributed to the localized electron field enhancement around the apex of the needle and the surface plasmon coupling originating from the periodic structure. This work demonstrates a new technique for producing controllable and reproducible SERS substrates potentially applicable for chemical and biological assays.

In this work, we report the synthesis of two new forms of WS2 nanostructures – freestanding WS2 trees and fibers on Au by chemical vapor deposition. It is observed that dislocation‐driven growth causes WS2 crystals to grow and merge in both vertical and horizontal directions to form the pyramidal tree. During the formation of WS2 fibers, the presence of two‐step growth was demonstrated. It is observed that sulphurization of WO3 nanoparticle leads to formation of WS2 rod in the first stage, followed by second stage in which selective growth causes some WS2 layers grow faster compared to other ones leading to the formation of fibrous WS2 structure. Fibers synthesized by our reported method have highly exposed WS2 layers which can demonstrate interesting catalytic and edge related properties or can be functionalized for future applications. [ABSTRACT FROM AUTHOR]

We have demonstrated the fabrication of Si- and Ge-incorporated carbon nanofibers (CNFs) at room temperature. Graphite foil surfaces were irradiated by Ar+ and Ne+ ions with simultaneous Si and Ge supply, and the dependences of the ion-induced composite CNFs surface morphology on the ion species and type of incorporated materials were investigated. The sample surfaces were characterized by various kinds of densely distributed nanostructures, such as conical protrusions, nanoneedles, nanocones, and CNF-tipped cones, depending on the Si and Ge supply rates during ion irradiation. In addition, Ne+ irradiation yielded longer CNFs compared to Ar+-irradiated CNFs. Thus, the nanostructures growth was controllable by adjusting the ion and material species. Surface morphology of ion-induced Ge-incorporated CNFs. [ABSTRACT FROM AUTHOR]

We demonstrate a unique strategy to fabricate highly transparent and flexible field electron emitters (FEEs) based on combined carbon nanostructures, i.e., conical nanocarbon structures (CNCSs) and single-walled carbon nanotubes (SWNTs). The combined structure was prepared by spray coating of 1,2-dichloroethane (DCE) dispersed SWNTs onto neon ion (Ne+) irradiation induced CNCSs on nafion substrate. The field emission (FE) property of SWCNTs on both flat nafion and CNCSs surfaces increased with increasing the SWCNTs amount. The best FE result was attained for the highest amount of SWCNTs on the CNCSs substrate. This kind of collective structures is found to be effective emitters on transparent and flexible ion-irradiated nafion substrate. Moreover, the combined carbon nanostructures showed improved transparency and emission performance compared to the individual nanostructures. The FE properties of 0.5 ml SWCNTs solution on CNCSs surfaces were equal to those of 1.5 ml SWCNTs solution on flat nafion surface. The hybrid structure based emitters (CNCSs and SWCNTs) produced by this method are lower-cost cathode materials than hybrid structures of SWCNTs and flat nafion. Thus the combined nanostructures of SWCNTs/CNCSs might have huge prospects for the fabrication of efficient transparent and flexible FEEs and their broad application in next-generation portable display devices. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Zinc oxide (ZnO) thin films grown on SiO2-coated Si substrates by filtered cathodic vacuum arc (FCVA) at 200°C was irradiated with Ar+ ions with a simultaneous supply of Fe atoms or with ions (without Fe) at room temperature to fabricate Fe- or N-doped ZnO nanoneedles, respectively. The morphological structure of the doped nanoneedles was almost identical with that of non-doped nanoneedles. The detailed analyses by energy dispersive X-ray spectroscopy combined with transmission electron microscope revealed that Fe was doped at and beneath the surface of the nanoneedles as well as at the needle tip. Random lasing was observed for both Fe- and N-doped ZnO nanoneedles thus fabricated, and the lasing peaks detected were redshifted compared with those attained for non-doped ZnO nanoneedles. Since the lasing wavelength, and hence the bandgap, was readily tunable, the combination of FCVA and ion-irradiation methods was concluded to be quite promising to fabricate 1D nanostructures for optoelectronics applications at low temperatures. [Copyright &y& Elsevier]

Abstract: For the direct fabrication of densely distributed one dimensional nanostructures on Si substrates, Si (100) surfaces were bombarded by obliquely incident 3keV Ar+ ions with a simultaneous supply of Mo seed atoms at various temperatures ranging from room temperature to 400°C. The surface sputtered at room-temperature with Mo seeding was characterized by the nanocones pointing in the direction of the incident ion beam. In addition, they possessed a so-called “web” at their acute-angle side. This web decreased in size with an increase in the sputtering temperature. Thus, the projections fabricated at elevated temperatures were featured by the nanorod-like structure rather than conical structure. With increasing the sputtering temperature, projections decreased in base diameter (from ∼90nm at 200°C to ∼50nm at 400°C) while they increased in both length (from ∼160nm at 200°C to ∼240nm at 400°C) and numerical density (from ∼5×107 mm−2 at 200°C to ∼1.2×108 mm−2 at 400°C). The controlled fabrication of such densely distributed one dimensional nanoprojections on Si using ion beam technique, we believe, would open up a variety of applications such as nanoelectronics and optoelectronics devices. [Copyright &y& Elsevier]

We have constructed a microprotrusion fabrication system consisting of a differentially pumped ion gun and a seed material supply source, both of which operate under an UHV condition. Using this system, Si (1 0 0) surfaces were bombarded by obliquely incident 3 keV Ar+ ions at room temperature with and without a simultaneous supply of Mo atoms. The sputtered surfaces without a Mo supply were flat or characterized by a nano-sized rippled structure, whereas those with simultaneous Mo seeding displayed densely distributed Mo-seeded cones. For a very low seeding rate of ∼7.2 × 10−2 nm/min, the optimum sputtering rate needed to induce seed cone growth over a sputtered crater was determined to be 4.4 nm/min. The size and number density of cones thus grown at the crater center were estimated to be 65–230 nm in width and ∼3 × 107 mm−2, respectively. The controlled fabrication of such seed cones may be applicable to the development of electron sources whose basic operational mechanism is field-electron emission. [Copyright &y& Elsevier]

The exciton radiative lifetime in ZnO nanorods is studied. It is found that the exciton radiative lifetime increases with temperature as T2. Furthermore, the spectral linewidth of the photoluminescence of the ZnO nanorods also increases with temperature as T2, suggesting a linear dependence of exciton radiative lifetime on the spectral linewidth. The physics behind is that the oscillator strength of excitons at k=0 is shared equally among all the states within the spectral linewidth and the coherence extension of an exciton decreases with temperature due to the scattering by phonons, defects, or impurities. [ABSTRACT FROM AUTHOR]