ZnO Nanonails Research Articles

Substrate effects on ZnO nanostructure growth via nanoparticle-assisted pulsed-laser deposition

The effects of various substrate conditions on the morphology, crystal structure and photoluminescence of ZnO nanostructures synthesized by nanoparticle-assisted pulsed-laser ablation deposition were investigated. It is concluded that the sapphire substrate with a 1 h anneal at 1000 °C is the most favorable to the vertical growth of ZnO nanostructures. SEM analysis indicates that the well-aligned diameter-modulated ZnO nanonails with unique shape were successfully synthesized on the annealed sapphire substrate. The as-synthesized ZnO nanostructures exhibit an ultraviolet emission at around 390 nm and the absent green emission under room temperature, indicating that there is a very low concentration of deep-level defects inside ZnO lattices. The novel ZnO nanostructures could offer novel opportunities for both fundamental research and technological applications.

Vertically aligned growth of ZnO nanonails by nanoparticle-assisted pulsed-laser ablation deposition

Vertically aligned ZnO nanonails have been successfully grown on annealed sapphire substrates at comparatively high gas pressure using catalyst-free nanoparticle-assisted pulsed-laser ablation deposition (NAPLD). The growth behavior of the ZnO nanonails has been investigated by variation of the ablation time, which we name ‘isolated particle initiated growth’ and a three-step growth mechanism for ZnO nanonails is proposed. SEM analysis reveals that each of the uniquely shaped ZnO nanonails consists of a so-called hexagonal rod-shaped ‘root’ and a slightly tapered ‘stem’. The well-aligned ZnO nanonails exhibit a strong ultraviolet (UV) emission at around 390 nm under room temperature and only negligible visible emission, which indicates that there is a very low concentration of oxygen vacancies in the highly oriented ZnO nanonails. The as-synthesized nanonail arrays on sapphire substrate could offer novel opportunities for both fundamental research and technological applications.

Low-temperature synthesis of ZnO nanonails

Wurtzite ZnO nanonails on silicon substrate were successfully synthesized by thermal vapor transport and condensation method at a low temperature without a metal catalyst. Pure Zn powders were used as raw material and O 2/Ar powders as source gas. The products were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the deposited nanostructures include aligned ZnO nanonails. The ZnO nanonails, with crystalline cap and small-diameter shafts, grow along the c-axis. The optical properties have been revealed by photoluminescence spectra. We considered that the ZnO nanonails growth is a vapor–solid process.

Simple Solvothermal Route To Synthesize ZnO Nanosheets, Nanonails, and Well-Aligned Nanorod Arrays

ZnO nanosheets, nanonails, and well-aligned nanorods were fabricated on Zn foils by a solvothermal approach using ethanol as the solvent. A lower synthesis temperature and a shorter time period favor the formation of nanosheets. By optimizing the synthesis temperature and time period, ZnO nanonails with a hexagonal cap and a long stem could be produced. A higher temperature was not favorable to produce uniform and smooth nanorods. Well-aligned ZnO nanorod arrays were produced with diameters within 100-250 nm and lengths up to approximately 6 microm when NaOH was added to the solvent. By optimizing the reaction parameters, the morphology, size, and orientation of the nanoforms could be tailored. The ZnO nanorods exhibit an excitonic strong UV emission and a defect-related broad green emission at room temperature. The defect-related green emission band decreased with the improvement of the degree of alignment of the nanorods.

Lasing in whispering gallery mode in ZnO nanonails

We report on the observation of ultraviolet lasing in optically pumped ZnO nanonails synthesized by thermal chemical vapor deposition method. The lasing threshold was found to be 17MWcm−2. Very sharp emission peaks (full width at half maximum of 0.08nm) were observed in the emission spectrum, indicating a high Q factor of the cavity formed by the hexagonally shaped nanonail head. The analysis of the lasing spectra strongly suggests the whispering gallery mode lasing from a hexagonally shaped head of the single ZnO nanonail.

Controllable Synthesis of ZnO Nanonails by Vapor-Solid Process: Growth Mechanism and Structural and Optical Properties

ABSTRACTSingle-crystalline with good optical properties aligned ZnO nanonails were grown on steel alloy substrate without the use of metal catalyst or additives by the thermal evaporation process using high purity metallic zinc powder and oxygen as source materials for zinc and oxygen, respectively. Detailed morphological studies by FESEM revealed that the obtained nanonails are grown in a high density over the whole substrate surface and are exhibiting perfect hexagonal-shaped caps. The diameters of the nanonails at their tops and bases are ranges from 120∼160nm and 50∼70 nm, respectively. The detailed structural characterizations confirmed that the synthesized nanostructures are single-crystalline and grown along the c-axis direction. Raman scattering and room-temperature photoluminescence studies demonstrated the wurtzite hexagonal phase and good optical properties, respectively for the grown nanonails.

Characterization and Field‐Emission Properties of Vertically Aligned ZnO Nanonails and Nanopencils Fabricated by a Modified Thermal‐Evaporation Process

AbstractVertically aligned ZnO nanonails and nanopencils are synthesized on a silicon substrate using a modified thermal‐evaporation process, without using a catalyst or predeposited buffer layers. An adiabatic layer is used to provide an abrupt temperature decrease and high gas concentration for the nanostructures growth. The structure and morphology of the as‐synthesized ZnO nanonails and nanopencils are characterized using X‐ray diffraction, and scanning and transmission electron microscopies. Raman and photoluminescence properties are also investigated at room temperature. Field‐emission characterization shows that the turn‐on fields for the vertically aligned ZnO nanonails and nanopencils are 7.9 and 7.2 V μm–1, respectively.

Controlled growth of semiconducting oxides hierarchical nanostructures

Semiconducting ZnO hierarchical nanostructure, where ZnO nanonails were grown on ZnO nanowires, has been fabricated under control experiment with a mixture of ZnO nanopowders and Sn metal powders. Sn nanoparticles are located at or close to the tips of the nanowires and the growth branches, serving as the catalyst for the vapor–liquid–solid growth mechanism. The morphology and microstructure of ZnO nanowire and nanonail were measured by scanning electron microscopy and high-resolution transmission electron microscopy. The long and straight ZnO nanowires grow along [0001] direction. ZnO nanonails are aligned radially with respect to the surface the ZnO nanowire. The long axis direction of nanonails forms an angle of ∼30° to the [0001] direction.

Growth of Self-Organized Hierarchical ZnO Nanoarchitectures by a Simple In/In2S3 Controlled Thermal Evaporation Process

Novel hierarchical ZnO nanoarchitectures, such as microtrepangs, microbelts, nanoflowers, nanocombs, nanowheels, and nanofans assembled by ZnO nanocones, nanobowling pins, nanobottles, nanoarrows, and nanonails, have had their growth controlled by the thermal evaporation of Zn and a mixture of In and In2S3. Both the morphologies of the products and their construction units could be efficiently controlled by simple adjustment of the weight ratio of In/In2S3. The phase structure, morphologies, and photoluminescence properties of the ZnO products were investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and photoluminescence spectroscopy. These novel hierarchical ZnO nanoarchitectures may be attractive building blocks for creating optical or other nanodevices.

Synthesis and Optical Properties of S-Doped ZnO Nanostructures: Nanonails and Nanowires

S-doped ZnO nanostructures such as nanonails and nanowires have been synthesized via a simple one-step catalyst-free thermal evaporation process on a large scale. The doping concentration of sulfur into ZnO nanonails and nanowire were 2 atm % and 7.5 atm %, respectively. Studies found that the S-doped ZnO nanonails and nanowires were single-crystalline wurtzite structure and grew along the (001) direction. The average diameters of the nanonails and nanowires were 70 and 50 nm, respectively. Low-temperature photoluminescence spectra of ZnO samples showed two luminescence peaks in the UV and green emission region, respectively. As the concentration of sulfur in the ZnO nanostructures increased, the intensity of the UV emission peak decreased dramatically, and it showed a little blue-shift while the intensity of the green emission increased greatly.

Morphology-controlled synthesis, growth mechanism and optical properties of ZnO nanonails

High-quality ZnO nanonails with different morphologies were synthesized on silicon substrate through a simple low-temperature thermal evaporation process. The obtained ZnO nanonails exhibit well-defined morphologies, single-crystalline orientations, and clean surface without amorphous contamination. The morphologies of the products can be easily controlled by simply tuning the evaporation temperature of indium powder ( T In). The optical properties of the products were studied by Raman and photoluminescence procedures. The growth of nanonails is based on firstly epitaxial sprouting of small nanorods and then the epitaxial growth of nanonails structures with different microstructures due to different zinc vapor pressures and different deposition sites.

Growth and Characterization of ZnO Nanonail

ABSTRACTZinc oxide (ZnO) is an interesting material for short-wavelength optoelectronics due to its wide band gap. The nanostructures of ZnO are also intriguing since a variety of morphology can be obtained by employing different processing parameters. In our laboratory, ZnO nanonails were successfully synthesized at low temperature using a thermal chemical vapor deposition. The morphology of the sample was studied by using scanning electron microscopy. The shape of the nail head can be controlled from hexagon to quasi-circular shape. X-ray diffraction, Raman scattering, photoluminescence spectroscopy were also performed to analyze the ZnO nanonail. Photoluminescence spectroscopy suggested that the defects in the ZnO nanonail and nanobone are of different nature.

Hierarchical oxide nanostructures

A variety of hierarchical oxide nanostructures, including ZnO nanonails on nanowires/nanobelts, ZnO nanorods on nanobelts, comb-like ZnO nanostructures, hierarchical MgO nanowires, etc., have been synthesized by thermal vapor evaporation and condensation. Observation of these nanostructures demonstrates the diversity of the geometry of these oxides in the nanoscale range. These nanostructures may be helpful in studies of nanostructure growth mechanisms and may find applications in nanoelectronics, opto-electronics, catalysts, displays, etc.

ZnO Nanobridges and Nanonails

Wurtzite ZnO nanobridges and aligned nanonails have been synthesized by thermal vapor transport and condensation method. The nanobridges have two rows of c-axis ZnO nanorods epitaxailly grown on the edges of the {0001} plane of the ZnO nanobelt. Some variations of the nanobridges have also been observed. The ZnO nanonails, with crystalline cap and small diameter shafts, grow along the c-axis. The shape of the nanonail cap and shaft varies. The nanobridges have very low concentration of indium in the structure and the nanonails are pure ZnO. These materials have potential in applications such as optoelectronics, etc.