Building crystalline Sb2S3 nanowire dandelions with multiple crystal splitting motif

Crystalline dandelion-like antimony (III) sulfide (Sb₂S₃) nanowires were synthesized by a PEG-assisted solvothermal process. The orthorhombic crystal structure and dandelion-like multi-branched nanowire morphology were revealed by X-ray diffractometry (XRD) and scanning electron microscopy (SEM) respectively. High-resolution transmission electron microscopy (TEM) identified that the highly crystalline Sb₂S₃ nanowires grew along the [001] direction with individual wire diameter of 195 ± 52 nm. The band gap of the Sb₂S₃ nanowires was measured to be ca. 1.67 eV. A combination of PEG-templated assembly and crystal splitting mechanism was likely responsible for the growth of the observed nanowire dandelion structures.     

Control of growth orientation and shape for epitaxially grown In2O3 nanowires on a-plane sapphire

Vertically aligned indium oxide nanowires were grown on a-plane sapphire substrate by the method of catalyst-assisted carbothermal reduction. The morphology and crystal structure of the nanowires are determined by X-ray diffraction, transmission electron microscopy and field-emission scanning electron microscopy. Two types of In₂O₃ nanowires were found by controlling the growth conditions. The nanowires with a hexagonal cross-section were shown to grow in [1 1 1] direction, whereas those with a square cross-section grow in [0 0 1] direction. In addition to the temperature effects, the concept of supersaturation in Au catalyst is proposed to explain the formation of these two types of nanowires. Besides, tapering, which is explained with the interplay between the vapor-liquid-solid and vapor-solid growth mechanisms, is observed in the nanowires.     

Growth and optical properties of uniform tungsten oxide nanowire bundles via a two-step heating process by thermal evaporation

Tungsten oxide (WO₃) nanowires with diameters of 15-40 nm and lengths of hundreds of nanometers were synthesized by thermal chemical vapor deposition (CVD) without using any catalyst in a low-temperature zone (200-300 °C) of a tube furnace via a two-step heating process. The morphology, composition, and crystal structure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS), Raman, ultraviolet UV-visible, and cathodoluminescence (CL) spectroscopy. XRD and TEM confirmed that the nanowires were triclinic WO₃ with growth direction along [001]. Blue emission was observed in both the UV-visible and CL spectrum, indicating that the WO₃ nanowires exhibited a red-shift at an optical absorption wavelength due to oxygen deficiencies. The crystallinity and size distribution of the nanowires influenced the bandgap. In the CL spectrum, the blue emission was at shorter wavelengths than reported previously, which can be attributed to the nanoscale size effect.     

Synthesis of K6Ta10.8O30 nanowires by molten salt technique

The synthesis of single crystalline K₆Ta_10.8O₃₀ nanowires by molten salt method was reported for the first time. X-ray diffraction results indicated that the as-prepared products were pure phase K₆Ta_10.8O₃₀. Scanning electron microscopy and transmission electron microscopy results showed that the products consisted of wire-like nanostructures with 100-300 nm in diameter and several micrometers in length. High resolution electron microscopy and selected area electron diffraction results indicated that the K₆Ta_10.8O₃₀ nanowires were single crystalline with a growth direction of [0 0 1]. The ultraviolet-visible diffuse reflectance measurement showed that the band gap of the nanowires was about 4.1 eV. The effects of reaction temperature, time, and weight ratio of the precursor (mixture of K₂CO₃ and Ta₂O₅) to KCl salt on the morphology of the products were investigated.     

Synthesis of MoO3 nanobelts by medium energy nitrogen ion implantation

Ion implantation has been revealed as a potential technique to modify the surface of materials. In this work, MoO₃ nanobelts were synthesized on MoO₃ whisker surfaces by means of ion implantation with 60 keV nitrogen ions at a dose of 1 × 10¹⁶ atom/cm² and characterized by scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. The result showed that the nanostructures of MoO₃ occurred over the whisker surfaces and had belt-like shapes. The size of the synthesized MoO₃ nanobelts mostly ranged from 20 to 60 nm in width and 300 to 800 nm in length. The nanobelts were found to have an orthorhombic crystal structure with growth preferential in the [001] direction. The growth process of the nanobelts based on the common vapor-solid mechanism is discussed.     

Molten salt synthesis of single-crystal Co3O4 nanorods

The synthesis of the single-crystal Co₃O₄ nanorods by molten salt approach was reported for the first time. The products were characterized by Transmission electron microscopy (TEM), X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM) and Selected-area electron diffraction (SAED). TEM results indicate that these nanorods have diameters of about 150 nm and lengths of about 2 μm. According to the analysis of the SAED and HRTEM results, we drew the conclusion that these nanorods grew along an unusual [− 1,− 1,15] direction by Ostwald ripening mechanism.     

Fabrication, structural and electrical characterization of VO2 nanowires

The structural and electrical properties of VO₂ nanowires synthesized on Si₃N₄/Si substrates or molybdenum grids by a catalyst-free vapour transport method were investigated. The grown VO₂ nanowires are single crystalline and rectangular-shaped with a preferential axial growth direction of [1 0 0], as examined with various structural analyses such as transmission electron microscopy, electron diffraction, X-ray diffraction, and X-ray photoelectron spectroscopy. In particular, it was found that growing VO₂ nanowires directly on Si₃N₄ deposited molybdenum transmission electron microscopy grids is advantageous for direct transmission electron microscopy and electron diffraction characterizations, because it does not involve a nanowire-detachment step from the substrates that may cause chemical residue contamination. In addition to structural analyses, VO₂ nanowires were also fabricated into field effect transistor devices to characterize their electrical properties. The transistor characteristics and metal-insulator transition effects of VO₂ nanowires were investigated.     

Structure of Pt3Co(1 1 0)c(2×4)-O surface studied by scanning tunneling microscopy

A Pt₃Co(1 1 0)c(2×4)-O surface has been investigated by scanning tunneling microscopy (STM), low-energy electron diffraction, and Auger electron spectroscopy. At a very initial oxidation stage exposed at 500°C, creation of missing and/or added row structures running to the [0 0 1] direction on clean Pt₃Co(1 1 0)2×1 surface was imaged from the steps. The surface is fully covered by a well-ordered c(2×4) structure at 2 L oxygen exposure. Atomic-resolution STM image shows the added row-type anti-phase Co-O zigzag chains along the [0 0 1] direction. Based on the images, the structure model for the c(2×4) surface was suggested as a first oxidized layer, which comes from the chemical reaction forming stoichiometric Co monoxide. Further oxygen exposure above 5 L, Co-O clusters imaged to large dots were formed on the surface with the size of about 5-7 Å.     

Ferroelectric properties of epitaxial Bi3.15Nd0.85Ti3O12 films on SiO2/Si using biaxially oriented MgO as templates

High quality epitaxial Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) thin films with thicknesses from 30 to 80 nm have been integrated on SiO₂/Si substrates. MgO templates deposited by ion-beam-assisted deposition and SrRuO₃ (SRO) buffer layers processed by pulsed laser deposition have been used to initiate the epitaxial growth of BNT films on the amorphous SiO₂/Si substrates. The structural and ferroelectric properties were investigated. Microstructural studies by X-ray diffraction and transmission electron microscopy revealed high quality crystalline with an epitaxial relationship of (001)_BNT||(001)_SRO||(001)_MgO and [100]_BNT||[110]_SRO||[110]_MgO. A ferroelectric hysteresis loop with a remanent polarization of 3.1 μC/cm² has been observed for a 30 nm thick film. The polarization exhibits a fatigue-free characteristic up to 1.44 × 10¹⁰ switching cycles.     

Effects of periodicity and oxygen partial pressure on the crystallinity and dielectric property of artificial SrTiO3/BaTiO3 superlattices integrated on Si substrates by pulsed laser deposition method

Epitaxial SrTiO₃(STO)/BaTiO₃(BTO) artificial superlattices have been grown on TiN buffered Si (001) substrates by pulsed laser deposition method and the effects of stacking periodicity and processing oxygen partial pressure on their crystallinity and dielectric properties were studied. The crystal orientation, epitaxy nature, and microstructure of STO/BTO superlattices were investigated using X-ray diffraction and transmission electron microscopy. The TiN buffer layer and superlattice thin films were grown with cube-on-cube epitaxial orientation relationship of [110](001)_films∣∣[110](001)_TiN∣∣[110](001)_Si. The c-axis lattice parameter of the STO/BTO superlattice decreased from 0.412 nm to 0.406 nm with increasing oxygen partial pressure and the dielectric constants, measured at the frequency of 100 kHz at room temperature, of the superlattices with 2 nm/2 nm periodicity increased from 312 at 1 × 10^− 5 Torr to 596 at 1 × 10^− 3 Torr. The dielectric constants of superlattices grown at oxygen partial pressure of 1 × 10^− 3 Torr increased from 264 to 678 with decreasing periodicity of the superlattices from 10 nm/10 nm to 1 nm/1 nm.     

Preparation of silicon carbide nanowires via a rapid heating process

Silicon carbide (SiC) nanowires were fabricated in a large quantity by a rapid heating carbothermal reduction of a novel resorcinol-formaldehyde (RF)/SiO₂ hybrid aerogel in this study. SiC nanowires were grown at 1500 °C for 2 h in an argon atmosphere without any catalyst via vapor-solid (V-S) process. The β-SiC nanowires were characterized by field-emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM) equipped with energy dispersive X-ray (EDX) facility, Fourier transformed infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The analysis results show that the aspect ratio of the SiC nanowires via the rapid heating process is much larger than that of the sample produced via gradual heating process. The SiC nanowires are single crystalline β-SiC phase with diameters of about 20-80 nm and lengths of about several tens of micrometers, growing along the [1 1 1] direction with a fringe spacing of 0.25 nm. The role of the interpenetrating network of RF/SiO₂ hybrid aerogel in the carbothermal reduction was discussed and the possible growth mechanism of the nanowires is analyzed.     

Synthesis and characterization of WO3 nanostructures prepared by an aged-hydrothermal method

Nanostructures of tungsten trioxide (WO₃) have been successfully synthesized by using an aged route at low temperature (60 °C) followed by a hydrothermal method at 200 °C for 48 h under well controlled conditions. The material was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Specific Surface Area (S_BET) were measured by using the BET method. The lengths of the WO₃ nanostructures obtained are between 30 and 200 nm and their diameters are from 20 to 70 nm. The growth direction of the tungsten oxide nanostructures was determined along [010] axis with an inter-planar distance of 0.38 nm.     

Formation of crystalline AlN nanotubes by a roll-up approach

In this study, aluminum nitride (h-AlN) nanotubes with high crystallinity and yield have been prepared by AlP and NaN₃ in a stainless steel autoclave at 350 °C. The samples were studied by powder X-ray diffraction pattern (XRD), transmission electron microscopy (TEM) and HRTEM in detail. The lengths of the AlN nanotubes are about 1 μm with most of the tube ends are open. The AlN nanotube preferentially grow along the [001] direction. The results demonstrate that the bending and roll-up of a thin layer to form tubular nanoscrolls is a thermally driven process. One-dimensional preferential growth was explained in terms of the crystallographic feature of hexagonal AlN.     

Microstructure of a-plane ZnO grown on LaAlO3 (001)

The microstructure of a-plane ZnO grown on LaAlO₃ (LAO) (001) has been systematically investigated by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Based on the results of XRD and TEM, only a-plane ZnO has been found to grow on LAO (001), and it consists of two types of domains perpendicular to each other. The crystal orientation relationships of a-plane ZnO domains with LAO have been verified to be [0001]_ZnO//[110]_LAO and [11?00]_ZnO//[11?0]_LAO. The domain boundaries in the a-plane ZnO are along the direction in a rotation angle of about 45° from the c-axes of ZnO. The surface morphology of ZnO films in SEM exhibits domain structure in stripe-like shape. The formation of two domains can be attributed to the cubic symmetry of the surface configuration of LAO (001).     

Synthesis and characterization of bismuth sulfide nanowires through microwave solvothermal technique

One-dimensional (1D) bismuth sulfide (Bi₂S₃) semiconducting nanowires have been successfully synthesized through mircrowave assisted solvothermal technique. The obtained product was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometry. The result shows that the Bi₂S₃ nanowires are single crystals grown along the [001] (c-axis) direction. The growth of Bi₂S₃ nanofibers with a preferential direction of c-axis can be ascribed to its particular structure. The optical measurement shows a blue shift relative to the bulk orthorhombic Bi₂S₃, which might be ascribed to the high aspect ratio of the nanowires.     

Uniform Bi2S3 nanowires: Structure, growth, and field-effect transistors

Large-scale single-crystalline Bi₂S₃ nanowires were prepared by a simple one-step hydrothermal reaction between Bi(NO₃)₃ and Na₂S₂O₃, without using any organics in the experiment. These Bi₂S₃ nanowires have uniform size diameters which are about 60 nm. The structure of the nanowires is determined to be of the orthorhombic phase, and the growth direction is along the [001] direction. The growth mechanism of the nanowires was investigated based on high-resolution transmission electron microscopy observations. The field-effect transistors (FETs) have been fabricated using a single Bi₂S₃ nanowire, n-type semiconductor behavior has been observed, and high on/off ratio of about 3 orders of magnitude has been achieved.     

Self-assembly growth of BiFeO3 powders prepared by microwave-hydrothermal method

With FeCl₃·6H₂O and Bi(NO₃)₃·5H₂O powder as raw materials and KOH as a mineralizer, the pure phase BiFeO₃ (BFO) powder was synthesized by microwave-hydrothermal (MH) method at 200 °C, with the reaction time as little as 30 min. The range of preparing the BFO powders had been summarized. The field emission scanning electron microscopy (FE-SEM) images revealed that the little BFO plate grew together forming rock sugar-like BFO powders, and then they grew further to form the mussel-like BFO powders. The transmission electron microscope (TEM) images also improved the self-assembly growth of BFO powders. The X-ray diffraction (XRD), the high resolution transmission electron microscopy (HRTEM) and the selected area electron diffraction (SAED) results indicated that the BFO powders grew along the [110] and [104] crystal orientation. The B-H loops of BFO indicated that the weak magnetism existed in the pure phase BFO powders.     

Hydrothermal synthesis and characterization of TiO2 nanorod arrays on glass substrates

Large-scale, well-aligned single crystalline TiO₂ nanorod arrays were prepared on the pre-treated glass substrate by a hydrothermal approach. The as-prepared TiO₂ nanorod arrays were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. X-ray diffraction results show that the main phase of TiO₂ is rutile. Scanning electron microscopy and transmission electron microscopy results demonstrate that the large-scale TiO₂ nanorod arrays grown on the pre-treated glass substrate are well-aligned single crystal and grow along [0 0 1] direction. The average diameter and length of the nanorods are approximately 21 and 400 nm, respectively. The photocatalytic activity of TiO₂ nanorod arrays was investigated by measuring the photodegradation rate of methyl blue aqueous solution under UV irradiation (254 nm). And the results indicate that TiO₂ nanorod arrays exhibit relatively higher photocatalytic activity.     

Fabrication of single-crystalline gallium nitride nanowires by using alginate as template

Hexagonal gallium nitride nanowires were synthesized successfully by solvothermal method with alginate as template. The microstructure, morphologies and compositions of the as-prepared product were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), and energy dispersive X-ray (EDX). Results suggested that the rod-like nanowires were hexagonal single-crystalline GaN growing along [001] direction. The photoluminescence spectra (PL) of the GaN revealed that the as-synthesized sample possesses excellent optical properties.     

Structure, growth and magnetic property of hard magnetic CoPtP nanowires synthesized by electrochemical deposition

This paper reports the electrochemical synthesis and characterization of one dimensional hard magnetic CoPtP nanowires. Three electrode potentiostatic electrochemical technique was used to deposit nanowires into a nanoporous track-etched polycarbonate membrane with a nominal pore diameter 50 nm and thickness around 6-9 μm. The room temperature electrolyte used for the deposition of nanowires consists of 60 g/lt CoSO₄7H₂O, 4.1 g/lt H₂PtCl₆, 4.5 g/lt NaHPO₂ and 25 g/lt B(OH)₃. The structural morphology was observed by scanning electron microscope and transmission electron microscope. The magnetic property of the nanowires was measured by vibrating sample magnetometer before removing the template. The coercive fields were measured to be 143 kA m^− 1 and 103 kA m^− 1 for parallel (H_║) and perpendicular to the nanowire axis, respectively. The higher coercivity value for H_║ indicating nanowires' easy magnetization direction lies along the nanowires' axis. The average composition of the CoPtP nanowires was determined by electron dispersive spectroscopy and the crystallinity was measured by X-ray diffractometer.