Formation of one-dimensional ZnO nanowires from screw-dislocation-driven two-dimensional hexagonal stacking on diamond substrate using nanoparticle-assisted pulsed laser deposition

Abstract: Insight into the controlled growth features of nanowires has been in the prominent spotlight for engineering the material properties Defect and dislocation induced nanowire growth has been emerging as a robust model by dwindling the conventional growth models In this context, we have proposed a screw dislocated Eshelby twist origin in cationic assimilated ZnO nanowires synthesized via Successive Ionic Layer Absorption and Reaction (SILAR) technique The growth of twisted nanowires occurred through a subsequent transformation from nanoflakes to nanoflowers Presence of twist contours in various zone axis pattern provided strong validation of Eshelby origin in twisted nanowires The preferential plane orientation of (0 0 0 2) confirmed the twisted growth along c-axis orientation Presence of screw tail at the twisted end of nanowire confirmed the influence of Peach-Kohler force acted on the screw axis Active vibrational modes and surface defect states of nanoflowers and nanowires were investigated and reported Twisted ZnO nanowires showed maximum sensing response of 291 towards 100 ppm of ammonia at room temperature with the lowest detection limit of 5 ppm The response and recovery times were found to be 39 and 17 s Influence of grain alignment, grain orientation and potential barrier height on ammonia sensing signatures are reported

Abstract: A novel fabrication method for single crystalline ZnO nanorods by pulsed laser deposition (PLD) using a chemical-bath-deposited ZnS seed layer is proposed. For the substrate temperature (Ts) lower than 700 °C, the PLD-ZnO showed a polycrystalline phase and film-type morphology, resulting from the ZnS seed layer with a cubic phase. However, the ZnS film became a sacrifical layer and single crystalline ZnO(002) nanorods can be achieved at Ts of 900 °C, where ZnS was decomposed to zinc metals and sulfur fumes. The transformation from ZnO film to nanorod microstructure was demonstrated with the change of ZnS layer into Zn grains. Enhanced performance of the metal-semiconductor-metal photodetectors were fabricated with ZnO/ZnS samples grown at Ts of 500, 700, and 900 °C. The responsivities (@1 V and 370 nm) of these three devices were 1.71, 6.35, and 98.67 A/W, while their UV-to-visible discrimination ratios were 7.2, 16.5, and 439.1, respectively. Obviously, a higher light-capturing efficiency was obtained in the 900 °C-grown ZnO/ZnS device owing to its one-dimensional nanostructure with high crystal quality. The results indicate PLD combined with a sacrifical nanostructure is a promising method for obtaining high-quality ZnO nanorods, which paves the way for the fabrication of high performance ZnO-based devices.

Abstract: We report on the growth of ZnO nanostructures in different gas ambient (Ar and N 2 ) using pulsed laser deposition technique. Despite the similar growth temperature, use of N 2 ambient gas resulted in well-aligned nanorods with flat surface at the tip, whereas, nanorods grown with Ar ambient exhibited tapered tips. The Nanorods grown under N 2 ambient exhibited additional Raman modes corresponding to N induced zinc interstitials. The nanorods are c-axis oriented and highly epitaxial in nature. Photoluminescence spectroscopy reveals that the UV emission can be significantly enhanced by 10 times for the nanorods grown under Ar ambient. The enhanced UV emission is attributed to the reduction in polarization electric field along the c-axis. n -ZnO nanorods/p-Si heterojunction showed rectifying I–V characteristics with a turn of voltage of 3.4 V.

Abstract: Triclinic (t-) Ba2V2O7 helical-like meso/nanosquares assembled from self-spiraling nanosheets have been controllably synthesized by a high-efficiency microwave irradiation-assisted surfactant process. The microstructure and morphology of the as-prepared t-Ba2V2O7 products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results show that the spirals of stacked nanosheets grow along the z-axis of microsquares, leading to the formation of a helical shape. Based on parallel experiments and theoretical analysis of t-Ba2V2O7 helical mesosquares at different reaction stages, the formation mechanism has been proposed to be a “self-assembly–dissolution–recrystallization–Ostwald-ripening” mechanism. The helical structures with uniform morphology and size may find promising applications in a variety of fields. The SDBS-assisted microwave irradiation method offers an easy path to the controllable fabrication of helical Ba2V2O7meso/nanomaterials, which can be readily extended to the development of functional structures of other alkaline earth vanadates. Moreover, it is found that the helical-like materials exhibit unique magnetic properties, corresponding to shape evolutions with different particle sizes at continuous reaction time.

Abstract: In the past decade, photo-detectors have been demonstrated to have very important applications in image sensing, optical communication, fire detection, environmental monitoring, space exploration, safety detection, and many other scientific research and industrial technology fields and are regarded as the key components of wearable devices. Compared to traditional fabrication approaches, pulsed-laser deposition (PLD)-grown materials for photo-detectors offer several merits. First, PLD is a clean physical vapor deposition approach. A stoichiometric amount of atoms can be transferred from the target to the substrate, avoiding complicated and potentially dangerous chemical reactions. Furthermore, the PLD process is carried out in a high-vacuum environment. Therefore, almost no contaminants, such as catalysts, precursors, surfactants and by-products, will be introduced. Also, the thickness of the films can be controlled by simply manipulating the energy and pulse number of the pulsed laser. Furthermore, the fabrication temperature is relatively low, which is available to deposit materials on various substrates, even flexible ones. Most importantly, PLD is a deposition technology with large area coverage, which can produce centimeter-scale thin films, the planar geometry of which has significant potential for compact device integration with modern semiconductor techniques. Consequently, this review introduces the recent advances on the materials, fabrication, and application of pulsed-laser deposition for a variety of high-performance photo-detectors from an overall perspective. Moreover, the challenges and future development trends are discussed.

Abstract: This article surveys recent developments in the rational synthesis of single-crystalline zinc oxide nanowires and their unique optical properties. The growth of ZnO nanowires was carried out in a simple chemical vapor transport and condensation (CVTC) system. Based on our fundamental understanding of the vapor–liquid–solid (VLS) nanowire growth mechanism, different levels of growth controls (including positional, orientational, diameter, and density control) have been achieved. Power-dependent emission has been examined and lasing action was observed in these ZnO nanowires when the excitation intensity exceeds a threshold (∼40 kW cm–2). These short-wavelength nanolasers operate at room temperature and the areal density of these nanolasers on substrate readily reaches 1 × 1010 cm–2. The observation of lasing action in these nanowire arrays without any fabricated mirrors indicates these single-crystalline, well-facetted nanowires can function as self-contained optical resonance cavities. This argument is further supported by our recent near-field scanning optical microscopy (NSOM) studies on single nanowires.

Abstract: The peak near 1150 cm 21 in the visible Raman spectra of poor quality chemical-vapor-deposited diamond is often used as the signature of nanocrystalline diamond. We argue that this peak should not be assigned to nanocrystalline diamond or other sp-bonded phases. Its wave number disperses with excitation energy, its intensity decreases with increasing excitation energy, and it is always accompanied by another peak near 1450 cm, which acts similarly. This behavior is that expected for sp-bonded configurations, with their smaller band gap. The peaks are assigned to transpolyacetylene segments at grain boundaries and surfaces.

Abstract: www.MaterialsViews.com C O M M U Direct Growth of Aligned Zinc Oxide Nanorods on Paper Substrates for Low-Cost Flexible Electronics N IC A By Afsal Manekkathodi , Ming-Yen Lu , Chun Wen Wang , and Lih-Juann Chen * IO N Contemporary science and technology are hoping to revolutionize modern society with soft portable electronic devices, such as rollup displays, wearable devices, electronic paper, chip smart cards, and basic components in various devices. Research is actively focused on using paper or paper-like substrates for basic electronics components, which make excellent alternative substrates with exceptional technological attributes and commercial perspectives for the many substrates available. [ 1–10 ] The innovative techniques and strategies that are required for these fl exible paper-like platforms are just beginning to emerge from research laboratories in the form of realistic prototypes and have yet to be commercialized. Various electronic devices have already been realized, such as electronic paper displays (EPDs), [ 2 ] printed circuit boards, [ 3 ] thin fi lm transistors (TFTs), [ 4 – 6 ] active-matrix organic light-emitting diodes (AMOLEDs), [ 7 ] paper batteries, [ 8 ]

Abstract: This paper reviews the recent progress in the preparation of oxide-based and heteroatom-doped particles. Surfactant-templated oxide particles, e.g. silica and titania, are possible candidates for various potential applications such as adsorbents, photocatalysts, and optoelectronic and biological materials. We highlight nanoporous oxides of one element, such as silicon or titanium, and those containing multiple elements, which exhibit properties that are not achieved with individual components. Although the multicomponent nanoporous oxides possess a number of attractive functions, the origin of their properties is hard to determine due to compositional/structural complexity. Particles with a well-defined size and shape are keys for a quantitative and detailed discussion on the unique complex properties of the particles. From this viewpoint, we review the synthesis techniques of the oxide particles, which are functionalized with organic molecules or doped with heteroatoms, the physicochemical properties of the particles and the possibilities for their photofunctional applications as complex systems.