Good Field Emission Properties Research Articles

Synthesis and photoluminescence, field emission properties of stalactite-like ZnS-ZnO composite nanostructures

Wurtzite stalactite-like quasi-one-dimensional ZnS nanoarrays with ZnO protuberances were synthesized through a thermal evaporation route. The structure and morphology of the samples are studied and the growth mechanism is discussed. X-ray diffraction (XRD) results show both the ZnS stem and the ZnO protuberances have wurtzite structure and show preferred [001] oriented growth. The photoluminescence and field emission properties have also been investigated. Room temperature photoluminescence result shows it has a strong green light emission, which has potential application for green light emitter. Experimental results also show that the stalactite arrays have a good field emission property, with turn-on field of 11.4 V/mu m, and threshold field of 16 V/mu m. The ZnO protuberances on the ZnS stem might enhance the field emission notably.

Effect of sputtered Cu film’s diffusion barrier on the growth and field emission properties of carbon nanotubes by chemical vapor deposition

Growth of carbon nanotube (CNT) films with good field emission properties on glass is very important for low cost field emission display (FED) applications. In addition to Ni, Co and Fe, Cu can be a good catalyst for CNT growth on glass, but due to diffusion into SiO2 it is difficult to control the CNTs density and uniformity. In this paper, four metal barrier layers (W, Ni, Cr, Ti) were deposited by dc magnetron sputtering on glass to reduce the Cu diffusion. As-grown CNT films showed various morphologies with the use of different barrier metals. CNTs with uniform distribution and better crystallinity can be synthesized only on Ti/Cu and W/Cu. Voltage current measurements indicate that better field emission properties of CNT films can be obtained on titanium and tungsten barriered Cu, while chromium and nickel are not suitable barrier candidates for copper in CNT-FED applications because of the reduced emission performance.

Horizontally aligned carbon nanotube field emitters having a long term stability

Horizontally aligned carbon nanotube (CNT) field emitters fabricated by electrophoresis deposition and fissure formation techniques show good field emission properties such as high current density, low turn-on voltage and long-term stability. Horizontally aligned multi-walled carbon nanotube (MWCNT) field emitters show an unusual very long-term stability, much better stability than the single-walled carbon nanotube (SWCNT) ones. The cause of the degradation is due to the heat generated by the resistance of CNTs. We were able to prevent effectively the degradation of the horizontally aligned field emitters by using MWCNTs and an additional deposition of aluminum on the CNT films, and the required time for 10% degradation is very long, 121 h.

Fabrication of an ultra-nanocrystalline diamond-coated silicon wire array with enhancedfield-emission performance

Large-area ultra-nanocrystalline diamond-coated silicon nanowire (UNCD/SiNW) field-emitterarrays were prepared by the deposition of ultra-nanocrystalline diamond (UNCD) on the tipsof arrays of silicon nanowires (SiNWs) with uniform diameters. The electron field-emission(EFE) behavior of UNCD/SiNW arrays as well as that of the SiNW arrays has beenobserved. The SiNWs exhibit good electron field-emission properties with turn-on fields(E0) ofabout 7.6 V µm−1, which is superior to the EFE properties of planar-silicon materials. The turn-on fieldsare related to the diameter of the SiNWs. Coating the SiNWs with a UNCDfilm further improves their EFE properties. The threshold field for attainingJe = 0.1 mA cm−2 EFE currentdensity is 16.0 V µm−1 forbare SiNWs and 10.2 V µm−1 for UNCD/SiNWs. The improvement in EFE properties due to the UNCD coating ispresumably due to the lower work function of field emission of the UNCD materials,compared to that of the silicon materials.

Fabrication and Field-Emission Performance of Zinc Sulfide Nanobelt Arrays

Large-scale, well-aligned, and oriented wurtzite ZnS nanobelt arrays have been synthesized by a simple template-free solvothermal reaction and subsequent heat-treatment process. The ZnS nanobelts grow along the [0001] direction perpendicularly on a zinc substrate, which have a thickness of about 30 nm, widths of several hundreds of nanometers, and uniform length up to 4 μm. The selection of Zn foil as the substrate is crucial for the formation of ZnS nanostructured arrays. The concentration of Zn ions, the pH value in the initial precursor solution, and the reaction temperature also have an important influence on the morphology of the final arrays. The formation of the nanobelt arrays are attributed to the structural compatibility of the substrate with ZnS and the growth-rate-dependence of morphology. Importantly, such nanostructured arrays show good field-emission properties with low turn-on fields (3.8 Vμm-1) and high field-enhancement factors (1839). This is attributed to the top edges and corners of t...

Enhanced Field Emission of Composite Au Nanostructured Networkon Si Nanoporous Pillar Array

Nanocrystallites Au particles are deposited on a well-alignedsilicon nanoporous pillar array (Si-NPA) surface through immersionplating to form an Au/Si-NPA composite system. It is found that a largenumber of Au nanoparticles are accumulated on the bottom of Si pillarsto form a regular network structure. By studying the field emissionproperties of such an Au/Si-NPA composite system, we find that theAu/Si-NPA exhibits good field emission properties, with staring fieldabout 2 V/μm and emission current density 67 μA/cm2 at7.59 V/μm. The enhanced field emission can be deduced from the uniquemorphology and structure of Au/Si-NPA.

Large scale SiC∕SiOx nanocables: Synthesis, photoluminescence, and field emission properties

Large scale, high yield SiC∕SiOx nanocables have been synthesized by thermal evaporation of carbon powders and silicon powders in the presence of Fe3O4 nanoparticle catalysts. Transmission electron microscopy and high-resolution transmission electron microscopy show that the nanocables consist of a 50–300nm single-crystalline β-SiC core wrapped with a 10–20nm amorphous SiOx shell. The nanocables have two broad photoluminescence peaks located around 390 and 460nm when the 250nm ultraviolet fluorescent light excitation is applied at room temperature. The results of field emission measurement of SiC∕SiOx nanocables indicate the low turn-on and threshold electric fields of 3.2 and 5.3V∕μm at the vacuum gap of 200μm, respectively. When the vacuum gap was increased to 1000μm, the turn-on and threshold electric fields were decreased to 1.1 and 2.3V∕μm, respectively. The SiC∕SiOx nanocables with good photoluminescence and field emission properties are promising candidates for ultraviolet-blue emitting devices, flat panel displays, and semiconductor field emitters.

Vertically Aligned 1D ZnO Nanostructures on Bulk Alloy Substrates: Direct Solution Synthesis, Photoluminescence, and Field Emission

We report a highly effective growth of vertically aligned ZnO one-dimensional (1D) nanostructures on conducting alloy substrate (Fe−Co−Ni) in mild solutions (T ≤ 70 °C) in the absence of any seeds, catalysts, and surfactants. The growth conditions such as NH3·H2O concentration, temperature, and nature of the substrate are correlated to affect the nanostructure formation. Different ZnO single-crystal nanostructures including nanoneedles, hexagonal nanorods, and nanopencils oriented normal to the substrate can be selectively formed in high quantity. The ordered ZnO nanostructures show strong UV excitonic emissions and good field emission (FE) properties. Other metal substrates such as Ti and Ni are also proven to be effective for ZnO nanoarray growth. Since metal substrates are much more economical and scalable than Si, sapphire/Al2O3, GaN, etc., we believe that our approach presents a general economical route toward mass production of controllable ZnO arrays and will facilitate flexible design of device ar...

A comparison between field-emission properties of three one-dimensional carbon materials

Electron field-emission characteristics from three types of one-dimensional carbon materials, including single-walled carbon nanotube (SWNT) rope, polyacrylonitrile-based carbon fiber tow, and carbon microtree, were compared. It is found that the SWNT rope exhibits the best field-emission (FE) properties of low-emission voltage, large field enhancement factor, and good stability, which are attributed to its perturbing nano-sized tip and numerous emission sites on the tip and body. Carbon microtree has the poorest FE property due to its high electrical resistivity. This work may provide useful information for the selection of cathode materials with good FE properties in the design of large current carbon-based FE cathodes.

Fabrication and field emission properties of regular hexagonal flowerlike ZnO nanowhiskers

Regular hexagonal flowerlike zinc oxide (ZnO) whiskers have been fabricated on the indium tin oxide electrodes with glass panel. A relatively simple hydrothermal growth process of low temperature is developed. The field emission properties of the flowerlike ZnO nanowhiskers have a low field emission threshold voltage (2.2V∕μm at a current density of 0.1μA∕cm2) and a high current density of 1mA∕cm2 at an applied field of 6.3V∕μm. The hydrothermal process method and good field emission properties indicate their potential application in field emission display device with glass panels.

Growth and field emission properties of tubular carbon cones

New forms of tubular carbon cone (TCC) were grown on gold wires by hot-filament chemical vapor deposition (HFCVD). They have a long-cone-shaped appearance with a herringbone hollow interior, surrounded by helical sheets of graphite that are coiled around it. It is considered that TCC formation results because the size of the catalyst particle located in the top of the TCC decreases continuously during growth, due to etching effects in the CVD plasma, reflecting competition between the growth and etching processes in the plasma. In addition, field emission measurements show that TCCs have a very low-threshold field of 0.27 V/μm, and that a stable macroscopic emitting current density of 1 mA/cm 2 can be obtained at only 0.5 V/μm. TCCs have good field emission properties, compared to other forms of carbon field emitter, and may be good candidates for use in field emission display devices.

Simulation studies of self-focusing carbon nanotube field emitter

It has been shown that carbon nanotubes exhibit good electron field emission properties, therefore have potential application in field emission displays as electron field emitters. In this study, the authors propose a new coplanar printed carbon nanotube (CNT) field emitter design that possesses symmetrical self-focusing properties without adding a focusing gate. A cylindrical gate electrode is located at the center and surrounded by the cathode. CNT paste can be applied to the cathode surface near or on the corner. A two-dimensional, particle-in-cell computer simulation code MAGIC was used to investigate the field emission characteristics of this new type of field emitter. Simulations were carried out for different gate voltages to investigate the effects on the emission current and beam divergence. Typical simulation parameters are anode voltage of 1000V, cathode voltage of 0V, and an anode-cathode distance of 95μm. It was found that there is an optimum gate voltage that gives the best focusing effect. The optimum gate voltages are different for different CNT paste locations. For CNT paste located on the round corner, with a radius of curvature of 0.5μm, an optimum negative gate voltage of about −15V is needed to push the overfocused emitted electrons to a focused spot having a current-weighted beam radius of 2.1μm. For a ring of CNT paste with 1μm width located on the flat surface next to the corner of the cathode, it would require an optimum gate voltage of about 45V to attract the emitted electrons to fall on a single spot on the anode having a current-weighted beam radius of 1.6μm. The electron emission can be turned off on individual emitter by applying a large negative gate voltage. This study shows the proposed simple field emitter design can produce well-focused electron beams for high resolution display applications.

Evolution of aluminum nitride nanostructures from nanoflower to thin film on silicon substrate by direct nitridation of aluminum precursor

Herein we demonstrate a convenient regulation of several aluminum nitride nanostructures through direct nitridation of aluminum precursor under different conditions. Different AlN nanostructures including conic nanoflowers, nanowires, quasi-aligned nanocones and polycrystalline thin film have been obtained on the Au-coated Si substrates just simply by decreasing the reaction temperature or changing the reaction procedure, and a four-stage growth mechanism is hereby deduced. The conic nanoflower composed of AlN nanocones is an interesting geometry. The photoluminescence and field emission measurement revealed that these AlN nanoflowers own a broad blue emission band and a rather good field emission property, suggesting the potential applications in light and field emission nanodevices.

Field emission from nanoforest carbon nanotubes grown on cobalt-containing amorphous carbon composite films

Nanoforest carbon nanotubes (CNTs) were synthesized by biased thermal chemical vapor deposition on cobalt-containing amorphous carbon composite films. The composite films were deposited on silicon by filtered cathodic vacuum arc using a Co-containing graphite target and then CNTs were grown at 580°C using the composite film as a catalyst layer. The nanoforest multiwalled CNTs have thin diameters between 10 and 20nm. Their tips point upwards while the rest is densely tangled. They exhibit good field emission properties with a low threshold field of 1.6V∕μm and a high current density of 2.1mA∕cm2 at 3V∕μm.

Different ZnO Nanostructures Fabricated by a Seed-Layer Assisted Electrochemical Route and Their Photoluminescence and Field Emission Properties

A simple seed-layer assisted electrochemical deposition (ECD) route has been successfully developed for preparation of different ZnO nanostructures, and their optical and field emission properties are also studied. ZnO films, nanowires, and nanosheets could be prepared in a rational way by just controlling the ECD current density. The corresponding growth mechanisms are also discussed on the basis of the characteristics of the ZnO crystal structure and the influences of the seed-layer and ECD current density. Except for ZnO nanosheets, both the room-temperature and low-temperature photoluminescence measurements of the ZnO films and nanowire arrays show strong ultraviolet excitonic emission, which proves their good crystal quality. Detailed analysis of the field emission (FE) properties indicates that the hierarchical ZnO nanowire array shows good FE property due to their high aspect ratio, small radius curvature, and proper density.

The application of single-walled carbon nanotubes in field emission display

Carbon nanotube field emission display has been regarded as one of the most promising flat panel displays due to its unique advantages. The morphology of the cathode material composed of the nanotubes will directly affect the field emission display properties. In this paper, we used single-walled carbon nanotubes synthesized by arc discharge method as the cathode material. This material was printed onto the conducting surface of the cathode plate using a screen-printing process. We studied the field emission properties of the cathode and the brightness of the green phosphor also screen printed on the anode. The display unit exhibited good field emission properties. The single-walled nanotube cathode was shown to have low turn-on voltage and high field emission current density.

Well-aligned zinc sulfide nanobelt arrays: Excellent field emitters

Large-scale, well-aligned and oriented wurtzite ZnS nanobelt arrays are fabricated by a simple solvothermal reaction and subsequent heat treatment. The nanobelts grow along the [0001] direction perpendicularly on a zinc substrate, which are about 30nm in thickness, several hundreds of nanometers in width, and up to 4μm in length. Importantly, such nanostructured arrays show a good field emission property with low turn-on field (3.8Vμm−1) and high field enhancement factor (∼1800), which is ascribed to the top edges and corners of the freestanding and well aligned nanobelts, and good electric contact with the conducting substrate where they grow.

Preparation and field emission properties of carbon nanotubes cold cathode using melting Ag nano-particles as binder

A new preparation process for carbon nanotubes (CNTs) cold cathode was studied through the replacement of traditional organic or inorganic binder with Ag nano-particles. This method has the advantages of low preparation temperature and fine electrical contact between CNTs paste and substrate. A mixture paste of CNTs, Ag nano-particles and other organic solvents was spreaded on Si substrate. By melting and connecting of Ag nano-particles after sintered 30 min at 250 °C, a flat CNTs films with good field emission properties was obtained. The measurements reveal that the turn on electric field and the threshold electric field of as-prepared CNTs cathode are 2.1 and 3.9 V/μm respectively and the field emission current density is up to 41 mA/cm 2 at an applied electric field of 4.7 V/μm.

Photoluminescence and field emission properties of ZnS:Mn nanoparticles synthesized by rf-magnetron sputtering technique

Nanoparticles of ZnS:Mn have been grown by radio frequency magnetron sputtering technique on glass and Si substrates at a substrate temperature 300K. X-ray diffraction patterns and selected area electron diffraction patterns confirmed the nanocrystalline cubic ZnS phase formation. TEM micrographs of the films revealed the manifestation of ZnS:Mn nanoparticles with an average size ∼6nm. UV–Vis–NIR spectrophotometric measurement showed that the films are highly transparent (∼90%) in the wavelength range 400–2600nm. From the measurements of transmittance spectra of the films the direct allowed bandgap values have been calculated and they lie in the range 3.89–4.12eV. The bandgap decreased with the increase of Mn concentration in the films. The Mn concentrations in the films have been varied from 0% to 8.9% and was measured by energy dispersive X-ray analysis. The photoluminescence of the Mn doped ZnS nanoparticles was measured. The intensity of the PL peaks at first increased with the increase of Mn concentration in the films up to 3.8% of Mn doping and at a Mn concentration higher than this, the intensity of PL peak decreased. Nanocrystalline ZnS:Mn showed good field emission property with a turn on field lying in the range 5.26–6.78V/μm for a variation of anode to sample distance from 60μm to 100μm.

Clean Carbon Nanotube Field Emitters Aligned Horizontally

Horizontally aligned carbon nanotube (CNT) field emitters, which strongly adhere to the substrate and show good field emission properties, were fabricated by electrophoresis deposition and fissure formation techniques. A thin film of CNTs was deposited on a substrate, by electrophoresis, from an aqueous mixture of CNT and detergent, and then the detergent was deposited also by electropholysis. CNTs with a clean surface were exposed in the fissures produced by firing. The field emission was increased significantly due to the additional deposition of the detergent. When the CNTs were cut by increasing the firing time, the field emission increased significantly, while their stability decreased considerably. Our method does not require any further treatment for field emission.