Selective growth of vertical ZnO nanowires on ZnO:Ga/Si[sub 3]N[sub 4]/SiO[sub 2]/Si templates (original) (raw)
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Vertical single-crystal ZnO nanowires grown on ZnO:Ga/glass templates
IEEE Transactions on Nanotechnology, 2005
Vertical single-crystal ZnO nanowires with uniform diameter and uniform length were selectively grown on ZnO : Ga/glass templates at 600 C by a self-catalyzed vapor-liquid-solid process without any metal catalyst. It was found that the ZnO nanowires are grown preferred oriented in the (002) direction with a small X-ray diffraction full-width half-maximum. Photoluminescence, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy measurements also confirmed good crystal quality of our ZnO nanowires. Field emitters using these ZnO nanowires were also fabricated. It was found that threshold field of the fabricated field emitters was 14 V/ m. With an applied electric field of 24 V/ m, it was found that the emission current density was around 0.1 mA/cm 2 Index Terms-Field emission, field-emission scanning electron microscopy (FESEM), glass, high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), vapor-liquid-solid (VLS) process, X-ray diffraction (XRD), ZnO nanowires.
Korean Journal of Chemical Engineering, 2006
Synthesis of ZnO nanowires was achieved on Si(100) substrate by the thermal evaporation of high purity metallic zinc powder without the use of any metal catalyst or additives. The diameter and length of the as-grown nanowires were in the range of 20–35 nm and few micrometers, respectively. The shapes and sizes of ZnO nanowires were dependent on the growth time. The high resolution transmission electron microscopy and selected area electron diffraction patterns indicated that the as-grown products are single crystalline with wurtzite hexagonal phase. Room temperature photoluminescence studies exhibited a strong UV emission and a suppressed green emission, confirming the good optical properties for the deposited nanowires.
Non-catalytic growth of high aspect-ratio ZnO nanowires by thermal evaporation
Solid State Communications, 2006
High-density and high aspect-ratio ZnO nanowires were grown on Si(100) substrates by the thermal evaporation of metallic zinc powder without the use of metal catalysts or additives. The as-grown nanowires had diameters in the range of 60-100 nm with lengths 5-15 µm. Detailed structural characterization indicated that the obtained nanowires are single-crystalline with a perfect hexagonal facet and surfaces. The room temperature PL spectrum exhibited strong UV emission, affirming that the as-grown products have good optical properties. The possible growth mechanism for the formation of hexagonal-faceted and perfect surface ZnO nanowires is also discussed.
A Comparison of ZnO Nanowires and Nanorods Grown Using MOCVD and Hydrothermal Processes
Journal of Electronic Materials, 2013
A comparison of ZnO nanowires (NWs) and nanorods (NRs) grown using metalorganic chemical vapor deposition (MOCVD) and hydrothermal synthesis, respectively, on p-Si (100), GaN/sapphire, and SiO 2 substrates is reported. Scanning electron microscopy (SEM) images reveal that ZnO NWs grown using MOCVD had diameters varying from 20 nm to 150 nm and approximate lengths ranging from 0.7 lm to 2 lm. The NWs exhibited clean termination/tips in the absence of any secondary nucleation. The NRs grown using the hydrothermal method had diameters varying between 200 nm and 350 nm with approximate lengths between 0.7 lm and 1 lm. However, the NRs grown on p-Si overlapped with each other and showed secondary nucleation. x-Ray diffraction (XRD) of (0002)-oriented ZnO NWs grown on GaN using MOCVD demonstrated a full-width at half-maximum (FWHM) of 0.0498 (h) compared with 0.052 (h) for ZnO NRs grown on similar substrates using hydrothermal synthesis, showing better crystal quality. Similar crystal quality was observed for NWs grown on p-Si and SiO 2 substrates. Photoluminescence (PL) of the NWs grown on p-Si and SiO 2 showed a single absorption peak attributed to exciton-exciton recombination. ZnO NWs grown on GaN/sapphire had defects associated with oxygen interstitials and oxygen vacancies.
High-quality ZnO nanowire arrays directly synthesized from Zn vapor deposition without catalyst
Journal of the Korean Crystal Growth and Crystal Technology
Vertically well-aligned ZnO nanowire (NW) arrays were synthesized directly on GaN/sapphire and Si substrate from Zn vapor deposition without catalysts. Experimental results showed that the number density, diameter, crystallinity and degree of the alignment of ZnO NWs depended strongly on both the substrate position and kind of the substrates used for the growth. The photoluminescence (PL) characteristics of the grown ZnO NW arrays exhibit a strong and sharp ultraviolet (UV) emission at 379 nm and a broad weak emission in the visible range, indicating that the obtained ZnO NWs have a high crystal quality with excellent optical properties. The as-grown ZnO NWs were characterized by using scanning electron microscopy (SEM), high resolution transmission electronic microscopy (HR-TEM), and X-ray diffraction (XRD).
An investigation into the catalyst-free growth of highly crystalline zinc oxide nanowires from metallic zinc powder on Si (100) substrate was investigated through the vapor solid (VS) process at 900◦C in a tube furnace. The effect of substrate position on the morphology, structure and photoluminescence (PL) properties of the fabricated ZnO nanowires was evaluated. The diameter of the resulted nanowires varies from 50 nm to 300 nm upon increasing the separation distance, between the substrate and the Zn powder source, from 12 cm to 16 cm. The EDX and XRD results showed that the zinc to oxygen ratio and the crystallinity of the fabricated nanowires are dependent on the substrate position. Also, the ratio of the UV to visible emission peaks of the fabricated ZnO nanowires was found to be strongly dependent on the substrate position. The PL spectra showed the enhancement in UV emissions for the samples fabricated on the substrate farther away from the Zn source with enhanced near band-edge emission for thicker nanowires. A possible mechanism for the growth of ZnO nanowires is discussed.
physica status solidi (a), 2012
Vertically well-aligned ZnO nanowire (NW) arrays were synthesized directly on Si(100) substrate without any metal catalysts by conventional thermal evaporation. The effects of the substrate positions on the structures and properties of ZnO NW arrays were primarily discussed. The orientation and morphology of the resultant NWs were analyzed by using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The experimental results showed that the density and diameter of the ZnO NWs can be effectively controlled by changing the substrate position. The photoluminescence (PL) characteristics of the grown ZnO NW arrays show a sharp and strong ultraviolet (UV) emission at 380 nm and a very weak green emission at around 490 nm, indicating that the assynthesized NWs have outstanding optical properties with good crystalline quality and may have excellent application potential in optoelectronic devices.
Low-Temperature Wafer-Scale Production of ZnO Nanowire Arrays
Angewandte Chemie-international Edition, 2003
Since the first report of ultraviolet lasing from ZnO nanowires, [1] substantial effort has been devoted to the development of synthetic methodologies for one-dimensional ZnO nanostructures. Among the various techniques described in the literature, evaporation and condensation processes are favored for their simplicity and high-quality products, but these gas-phase approaches generally require economically prohibitive temperatures of 800-900 8C. [2] Despite recent MOCVD schemes that reduced the deposition temperature to 450 8C by using organometallic zinc precursors, the commercial potential of gas-phase-grown ZnO nanowires remains constrained by the expensive and/or insulating (for example, Al 2 O 3 ) substrates required for oriented growth, as well as the size and cost of the vapor deposition systems. A low-temperature, large-scale, and versatile synthetic process is needed before ZnO nanowire arrays find realistic applications in solar energy conversion, light emission, and other promising areas.
Study of the Substrate Influence in ZnO Nanowires Oriented Growth
Procedia Materials Science, 2015
A solution growth approach for zinc oxide (ZnO) nanowires is highly appealing because of the low growth temperature and possibility for large area synthesis. In our work, ZnO nanowires were obtained from thin films prepared on silica glass, Si (100) and Si (111) from a single and five layers spin-coating deposition of a sol-gel prepared with dehydrate zinc acetate, monoethanolamine and isopropanol. Crystallization annealing was performed at 450 °C. These films were used as seed layer to prepare ZnO nanowires/nanorods from a zinc nitrate and hexamethylenetetramine solution. X-ray diffraction analysis showed that nanowires/nanorods grown on Si (111) were preferentially orientated along the [002] direction.
Effects of Deposition Parameters of Hydrothermal Method on Synthesis of ZnO-based Nanowires
Sensors and Materials, 2019
(NO 3) 2 ‧6H 2 O, ZnO-based nanowires, growth time ZnO-based nanomaterials can be used as sensors for different applications, including gas and ultraviolet (UV) ray sensors. To grow ZnO nanowires by the hydrothermal method, a ZnO seed layer was prepared by a sputtering method to deposit ZnO films on SiO 2 /Si substrates of about 200 nm thickness. Next, Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 were used as reagents, and DI water was used as a solvent, and they were mixed to the designed compositions. We found that when Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 were used as reagents to grow ZnO nanostructured materials, growth temperature, the concentration of the diluted solution, growth time, and the position of the substrates were four important factors affecting the synthesis results. The surface morphologies of ZnO nanowires were observed by field-emission scanning electron microscopy (FESEM), and crystalline phases were analyzed using X-ray diffraction (XRD) patterns. The FESEM images and XRD patterns were used to determine the effects of synthesis parameters on the morphologies and crystalline properties of the grown nanostructured materials. First, we found that 100 ℃ was the optimum synthesis temperature for growing pure ZnO nanowires, because ZnO-based nanowires could be successfully synthesized at different concentrations of Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 and different synthesis times. The effects of growth time, the position of the substrates on the carry sheet glass, and concentrations of Zn(NO 3) 2 ‧6H 2 O and C 6 H 12 N 4 on the growth of nanostructured materials were also investigated.