Showing papers on "Field electron emission published in 2017"
TL;DR: In this article, a series of ultrathin multilayered structure cathodes (UTMC) is constructed to simulate the field emission (FE) process of nanostructured semiconductor film cathodes.
Abstract: Considering the effect of both the buffer layer and substrate, a series of ultrathin multilayered structure cathodes (UTMC) is constructed to simulate the field emission (FE) process of nanostructured semiconductor film cathodes (NSFCs). We find a generalized FE mechanism of the NSFCs, in which there are three distinct FE modes with the change of the applied field. Our results clearly show significant differences of FE between conventional emitters and nanofilm emitters, which the non-Fowler-Nordheim characteristics and the resonant FE will be inevitable for NSFCs. Moreover, the controllable FE can be realized by fine-tuning the quantum structure of NSFCs. The generalized mechanism of NSFCs presented here may be particularly useful for design high-speed and high-frequency vacuum nano-electronic devices.
488 citations
TL;DR: Zinc oxide (ZnO) nanostructures were successfully incorporated into carbon nanotubes (CNTs) using an arc discharge method as discussed by the authors, which revealed that ZnO nanoparticles were attached on the exterior of CNTs.
130 citations
80 citations
TL;DR: In this paper, an enhancement in boiling heat transfer is reported through surface modification of Cu substrate by crystalline TiO2 nanostructure coating, which was done by electron beam evaporation technique on copper substrate at different thickness.
69 citations
TL;DR: In this article, the experimental study of nucleate pool boiling heat transfer characteristics of saturated water on SiO2 nanostructure surface at atmospheric pressure was reported, where the nanostructures were studied by X-ray diffraction, field emission scanning electron microscopic measurement, and atomic force microscope measurement.
69 citations
TL;DR: In this article, NiFe2O4 nano-crystallites with an average diameter of 8.9 nm were synthesized via hydrothermal method and the single-phase spinel structure was confirmed from X-ray diffractograms.
Abstract: NiFe2O4 nano-crystallites with an average diameter of 8.9 nm are synthesized via hydrothermal method. The single-phase spinel structure is confirmed from X-ray diffractograms. Morphology is analysed by transmission and field emission scanning electron microscopes. High specific surface area of 55.7 m2 g−1 is obtained for nano-particles. The M– H loop and M– T curve behaviours are investigated by vibrating sample magnetometry. The optical band gap energy is estimated from the UV–visible spectrum. In addition, the frequency dependence of dielectric properties is investigated. Cole–Cole plots are drawn to study electrical conduction mechanism and the kind of relaxation—Debye or non-Debye type. Low a.c. conductivity and low magnetic losses are noticed at 5 MHz frequency, which are suitable for microwave device applications.
63 citations
TL;DR: Graphenes are beneficial to electrons field emission due to its high aspect ratio, high carrier density, the larger carrier mobility, excellent electrical and thermal conductivity, excellent mechanical strength and chemical stability as mentioned in this paper.
Abstract: Graphenes are beneficial to electrons field emission due to its high aspect ratio, high carrier density, the larger carrier mobility, excellent electrical and thermal conductivity, excellent mechanical strength and chemical stability. In recent years, graphene or reduced oxide graphene field emitters have been successfully constructed by various methods such as chemical vapor deposition, chemical exfoliation, electrophoretic deposition, screen-printing and chemical synthesis methods. Graphene emitters are tried to construct in distribution with some angles or vertical orientation with respect to the substrate surface. The vertical alignment of graphene sheets or edges arrays can facilitate efficient electron emission from the atomically thick sheets. Therefore they have even more a low turn-on and threshold-field electronic field, high field enhancement factor, high current stability and high luminance. In this review, we shortly survey and discuss recent research progress in graphene field emission properties with particular an emphasis on their preparing method, characterization and applications in devices especially for vertical graphene and single layer graphene, also including their challenges and future prospects.
62 citations
TL;DR: In this paper, the enhanced field emission properties of three-dimensional (3D) mixed transition metal oxide with reduced graphene oxide nanosheets (rGO-NSs) using a simple and fast synthesis route were reported.
60 citations
TL;DR: In this paper, a comparative study of Pulsed Laser Deposition (PLD) based Tin Oxide (SnO 2 ) thin films deposited at various substrate deposition temperature (Ts) has been performed.
60 citations
TL;DR: In this paper, the authors show that due to linear energy dispersion, the traditional thermionic emission and field emission models are no longer valid for graphene and two-dimensional Dirac-like materials.
Abstract: The theories of thermionic emission and field emission (also known as the Richardson–Dushman [RD] and Fowler–Nordheim [FN] Laws, respectively) were formulated more than 80 years ago for bulk materials. In single-layer graphene, electrons mimic massless Dirac fermions and follow relativistic carrier dynamics. Thus, their behavior deviates significantly from the nonrelativistic electrons that reside in traditional bulk materials with a parabolic energy-momentum dispersion relation. In this article, we assert that due to linear energy dispersion, the traditional thermionic emission and field emission models are no longer valid for graphene and two-dimensional Dirac-like materials. We have proposed models that show better agreement with experimental data and also show a smooth transition to the traditional RD and FN Laws.
59 citations
TL;DR: In this paper, a hollowed-out hierarchical Co3O4 microrod-like structure assembled by interlaced thin nanosheets (with thickness of around 7nm) was evaluated.
Abstract: Hollowed-out hierarchical Co3O4 microrods has been synthesized via the interfacial-reaction of CoC2O4·2H2O with NaOH. Field emission scanning electron microscopic and transmission electron microscopic results revealed that the Co3O4 samples were hollowed-out hierarchical microrod-like structure assembled by interlaced thin nanosheets (with thickness of around 7 nm). The gas sensing properties of the porous microrods Co3O4 were evaluated. The response/recovery time of the gas sensor to 100 ppm methanol and ethanol are 0.8/7.2 s and 0.8/10.8 s, respectively. Gas sensing measurement revealed that the hollowed-out hierarchical Co3O4 microrods exhibit high performance, especially fast response/recovery characteristics to methanol and ethanol. The enhancement of gas sensing properties is attributed to the thin thickness of nanosheets, large specific surface area, loose interior and through-pore structure. The good sensing performance suggests this hollowed-out hierarchical Co3O4 microrods could be a promising candidate as a sensing material for real-time monitoring gas sensor.
TL;DR: The results indicate that ZnO nanowires could be applied in large area FEAs and good gate-controlled characteristics and the display of video images are realized.
Abstract: Zinc oxide (ZnO) nanowires are prepared for application in large area gated field emitter arrays (FEAs). By oxidizing Al-coated Zn films, the population density of the ZnO nanowires was tuned precisely by varying the thickness of the Al film. The nanowire density decreased linearly as the thickness of the Al film increased. Optimal field emission properties with a turn-on field of 6.21 V μm–1 and current fluctuations less than 1% are obtained. This can be explained by the minimized screening effect and good electrical conductivity of the back-contact layer. The mechanism responsible for the linear variation in the nanowire density is investigated in detail. Addressable FEAs using the optimal ZnO nanowire cathodes were fabricated and applied in a display device. Good gate-controlled characteristics and the display of video images are realized. The results indicate that ZnO nanowires could be applied in large area FEAs.
TL;DR: In this paper, the synthesis of palladium-graphene oxide based (Pd-rGO) composite and its enhanced electron field emission studies is reported. But, the Pd-CNTs-RGO composite exhibits lower turn-on field, lower threshold field, larger field enhancement factor and high emission current stability.
TL;DR: In this paper, a series of LuNbO4:xDy3+ (x = 0.20) phosphors were prepared using a high-temperature solid-state reaction technique.
Abstract: A series of LuNbO4:xDy3+ (x = 0–0.20) phosphors was prepared using a high-temperature solid-state reaction technique. X-ray diffraction (XRD) along with Rietveld refinement, field emission scanning electron microscopy (FE-SEM) observations, diffuse reflectance spectra (DRS), UV-vis photoluminescence (PL), fluorescence decays, PL quantum yields (QYs), and low-voltage cathodoluminescence (CL) were employed to characterize the phosphors. Nonradiative relaxation and host sensitization dramatically influence the LuNbO4:Dy3+ luminescence spectra and decay dynamics. It is shown that cross-relaxation arising from electric dipole–dipole interactions between adjacent Dy3+ ions is the leading mechanism of quenching the Dy3+ emission. The host sensitization for Dy3+ emission in LuNbO4 was confirmed and the energy transfer efficiency from the host to Dy3+ increased with increasing Dy3+ doping concentration/temperature. Upon excitation with ultraviolet light (261 nm) and a low-voltage electron beam (2 kV, 127 μA cm−2), the synthesized LuNbO4:Dy3+ phosphors show both the blue broadband emission of the LuNbO4 host and the characteristic emission of Dy3+ (the dominant one is the 4F9/2 → 6H13/2 transition, yellow), and the luminescence colour of the LuNbO4:Dy3+ phosphors can be tuned over a large gamut of colours by varying the Dy3+ doping concentration, and a single-phase intense white-light-emission has been achieved in the LuNbO4:0.015Dy3+ phosphor. On the basis of the good UV-vis PL and CL properties, LuNbO4:Dy3+ phosphors might be promising for applications in UV light-emitting diodes (UV-LEDs) and field emission displays (FEDs).
TL;DR: In this article, the structure and photoelectrochemical properties of CuWO4 porous films synthesized by a co-precipitation method followed by a hydrothermal treatment were investigated.
TL;DR: It is proved that FE can be enhanced by covering the InP NCs with graphene, and it is shown that InP/p-Si junction has a rectifying behavior, while graphene on InP creates an ohmic contact.
Abstract: We report the observation of field emission from InP nanocrystals epitaxially grown on an array of p-Si nanotips. We prove that field emission can be enhanced by covering the InP nanocrystals with graphene. The measurements are performed inside a scanning electron microscope chamber with a nano-controlled W-thread used as an anode. We analyze the field emission by Fowler-Nordheim theory and find that the field enhancement factor increases monotonically with the spacing between the anode and the cathode. We also show that InP/p-Si junction has a rectifying behavior, while graphene on InP creates an ohmic contact. Understanding the fundamentals of such nanojunctions is key for applications in nanoelectronics.
TL;DR: It was the FN electron tunneling that induced a substantial reduction in breakdown strength for the PP/nAl nanocomposites, and internal electronic conduction led to significant dielectric nonlinearity at high poling fields.
Abstract: Polymer/metallic particle nanocomposites or nanodielectrics can exhibit colossal dielectric constants with a relatively low dissipation factor under low electric fields and thus seem to be promising for high-energy density dielectric capacitors. To study this possibility, this work focused on the dielectric performance and loss mechanisms in polypropylene (PP)/aluminum nanoparticle (nAl NP) composites under high electric fields. Phosphonic acid-terminated poly(ethylene-co-1-butene) was grafted to the Al2O3 surface layer on the nAl NPs in order to achieve reasonable dispersion in the PP matrix. The dielectric breakdown study showed that the breakdown strength decreased to nearly 1/20 that of the neat PP film as the nAl content increased to 25.0 vol %. The leakage current study revealed three electronic conduction mechanisms in the PP/100 nm nAl nanocomposites, namely, ohmic conduction at low fields, hopping conduction at intermediate fields, and Fowler–Nordheim (FN) field electron emission above a critical...
TL;DR: In this article, a single carbon nanotube (CNT) fiber with different anode-cathode (AK) gap distances was studied, and the authors found that the field enhancement factor depends strongly on the finite AK gap distance.
Abstract: This paper studies field emission (FE) from a single carbon nanotube (CNT) fiber with different anode-cathode (AK) gap distances. It is found that the field enhancement factor depends strongly on the finite AK gap distance, due to the combination of geometrical effects and possible fiber morphology change. The geometrical effects of AK gap distance on the field enhancement factor are confirmed using COMSOL simulations. The slope drop in the Fowler-Northeim (FN) plot of the FE data in the high voltage is related to the electrical contact resistance between the CNT fiber and the substrate. It is found that even a small series resistance to the field emitter (<30% of the emission gap impedance) can strongly modify the FE characteristics in the high voltage regime, inducing a strong deviation from the linear FN plot.
TL;DR: In this paper, a generalized Fowler-Nordheim (FN) type equation is proposed to describe the reduced space-dimensionality seen by the quantum mechanically tunneling electron at a rough, irregular emission surface.
Abstract: The theories of field electron emission from perfectly planar and smooth canonical surfaces are well understood, but they are not suitable for describing emission from rough, irregular surfaces arising in modern nanoscale electron sources. Moreover, the existing models rely on Sommerfeld's free-electron theory for the description of electronic distribution which is not a valid assumption for modern materials with nonparabolic energy dispersion. In this paper, we derive analytically a generalized Fowler-Nordheim (FN) type equation that takes into account the reduced space-dimensionality seen by the quantum mechanically tunneling electron at a rough, irregular emission surface. We also consider the effects of non-parabolic energy dispersion on field-emission from narrow-gap semiconductors and few-layer graphene using Kane's band model. The traditional FN equation is shown to be a limiting case of our model in the limit of a perfectly flat surface of a material with parabolic dispersion. The fractional-dimension parameter used in this model can be experimentally calculated from appropriate current-voltage data plot. By applying this model to experimental data, the standard field-emission parameters can be deduced with better accuracy than by using the conventional FN equation.
TL;DR: This study further extends GaAs technology to vacuum electronics applications by observing observations of field emission from self-catalyzed GaAs nanowires grown on Si and showing that the presence of a Ga catalyst droplet suppresses the emission of current from the nanowire tip.
Abstract: We report observations of field emission from self-catalyzed GaAs nanowires grown on Si (111). The measurements were taken inside a scanning electron microscope chamber with a nano-controlled tungsten tip functioning as anode. Experimental data were analyzed in the framework of the Fowler-Nordheim theory. We demonstrate stable current up to 10−7 A emitted from the tip of single nanowire, with a field enhancement factor β of up to 112 at anode-cathode distance d = 350 nm. A linear dependence of β on the anode-cathode distance was found. We also show that the presence of a Ga catalyst droplet suppresses the emission of current from the nanowire tip. This allowed for the detection of field emission from the nanowire sidewalls, which occurred with a reduced field enhancement factor and stability. This study further extends GaAs technology to vacuum electronics applications.
TL;DR: In this paper, a near UV-light downconvertible narrow-band red emitting europium (0.5-7 m) was synthesized by a combustion method taking urea as fuel.
TL;DR: In this work, experiment-assisted fundamental aspects of the origin of dislocation contrast are studied and a dislocation dipole is observed and fully characterized for the first time in an SEM.
Abstract: Nowadays Field Emission Gun-Scanning Electron Microscopes provide detailed crystallographic information with high spatial and angular resolutions, and allow direct observation of crystalline defects, such as dislocations, through an attractive technique called Electron Channeling Contrast Imaging (ECCI). Dislocations play a crucial role in the properties of materials and ECCI has naturally emerged as an adapted tool for characterizing defects in bulk specimen. Nevertheless, fine control of the channeling conditions is absolutely required to get strong dislocation contrast for achieving comprehensive analysis. In this work, experiment-assisted fundamental aspects of the origin of dislocation contrast are studied. Experimentally, the potential of ECCI is explored in several dislocation configurations in Interstitial-Free steel (Fe − 1% Si) used as a model material. Full interpretations of dislocation contrast in (g, −g) and its evolution along the Kikuchi band are shown. Furthermore, a dislocation dipole is observed and fully characterized for the first time in an SEM.
TL;DR: It is concluded that ultrasmall Si nanovolumes cannot be efficiently P-doped and non-radiative recombination via interstitial-P induced states as quenching mechanism is proposed.
Abstract: Phosphorus doping of silicon nanostructures is a non-trivial task due to problems with confinement, self-purification and statistics of small numbers. Although P-atoms incorporated in Si nanostructures influence their optical and electrical properties, the existence of free majority carriers, as required to control electronic properties, is controversial. Here, we correlate structural, optical and electrical results of size-controlled, P-incorporating Si nanocrystals with simulation data to address the role of interstitial and substitutional P-atoms. Whereas atom probe tomography proves that P-incorporation scales with nanocrystal size, luminescence spectra indicate that even nanocrystals with several P-atoms still emit light. Current-voltage measurements demonstrate that majority carriers must be generated by field emission to overcome the P-ionization energies of 110–260 meV. In absence of electrical fields at room temperature, no significant free carrier densities are present, which disproves the concept of luminescence quenching via Auger recombination. Instead, we propose non-radiative recombination via interstitial-P induced states as quenching mechanism. Since only substitutional-P provides occupied states near the Si conduction band, we use the electrically measured carrier density to derive formation energies of ~400 meV for P-atoms on Si nanocrystal lattice sites. Based on these results we conclude that ultrasmall Si nanovolumes cannot be efficiently P-doped.
TL;DR: In this article, the authors explored superior flexible field emitters based on single-crystalline 3C-SiC nanowires, which had numbers of sharp edges, as well as corners surrounding the wire body and B dopants.
Abstract: Low turn-on fields together with boosted stabilities are recognized as two key factors for pushing forward the implementations of the field emitters in electronic units In current work, we explored superior flexible field emitters based on single-crystalline 3C-SiC nanowires, which had numbers of sharp edges, as well as corners surrounding the wire body and B dopants The as-constructed field emitters behaved exceptional field emission (FE) behaviors with ultralow turn-on fields (Eto) of 094–068 V/μm and current emission fluctuations of ±10–34%, when subjected to harsh working conditions under different bending cycles, various bending configurations, as well as elevated temperature environments The sharp edges together with the edges were able to significantly increase the electron emission sites, and the incorporated B dopants could bring a more localized state close to the Fermi level, which rendered the SiC nanowire emitters with low Eto, large field enhancement factor as well as robust current e
TL;DR: In this paper, a 120-µm-thick buckypaper was produced from aligned carbon nanotubes and measured by means of a nano-controlled metallic tip acting as collector electrode.
Abstract: We produce 120-µm-thick buckypapers from aligned carbon nanotubes. Transport characteristics evidence ohmic behavior in a wide temperature range nonlinearity appearing in the current–voltage curves only close to 4.2 K. The temperature dependence of the conductance shows that transport is mostly due to thermal fluctuation-induced tunneling, although to explain the whole temperature range from 4.2 to 430 K a further linear contribution is necessary. The field emission properties are measured by means of a nano-controlled metallic tip acting as collector electrode to access local information about buckypaper properties from areas as small as 1 µm2. Emitted current up to 10−5 A and turn-on field of about 140 V/µm are recorded. Long operation, stability and robustness of emitters have been probed by field emission intensity monitoring for more than 12 h at pressure of 10−6 mbar. Finally, no tuning of the emitted current was observed for in-plane applied currents in the buckypaper.
TL;DR: In this article, the effect of annealing of 3D porous hierarchical nanostructures on field emission and photocatalytic performances is studied, and the authors demonstrate the field emission characteristics of ZnCo2O4 marigold flowers synthesized via a facile hydrothermal method.
TL;DR: In this paper, a comparison between metal induced etching (MIE) and laser induced etch (LIE) was made by comparing the observed surface morphologies using SEM, and a single photoluminescence peak at 1.96 eV corresponding to red emission at room temperature was observed.
Abstract: Porous silicon (p-Si), prepared by two routes (metal induced etching (MIE) and laser induced etching (LIE)) have been studied by comparing the observed surface morphologies using SEM. A uniformly distributed smaller (submicron sized) pores are formed when MIE technique is used because the pore formation is driven by uniformly distributed metal (silver in present case) nanoparticles, deposited prior to the porosification step. Whereas in p-Si, prepared by LIE technique, wider pores with some variation in pore size as compared to MIE technique is observed because a laser having gaussian profile of intensity is used for porosification. Uniformly distribute well-aligned Si nanowires are observed in samples prepared by MIE method as seen using cross-sectional SEM imaging. A single photoluminescence (PL) peak at 1.96 eV corresponding to red emission at room temperature is observed which reveals that the Si nanowires, present in p-Si prepared by MIE, show quantum confinement effect. The single PL peak confirms the presence of uniform sized nanowires in MIE samples. These vertically aligned Si nanowires can be used for field emission application.
TL;DR: In this article, a template-free hydrothermal process was used to synthesize Dy2WO6-ZnO, which exhibited high reusability without appreciable loss of catalytic activity up to four runs and exhibited higher electrocatalytic activity than the prepared ZnO for methanol electrooxidation in alkaline medium.
Abstract: In this article we report the fabrication of 3 wt% Dy2WO6 doped ZnO via a template-free hydrothermal process and its photocatalytic activity against azo dyes Rhodamine-B (Rh-B) and Trypan Blue (TB) in solar light irradiation. The as prepared Dy2WO6 doped ZnO was characterised by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution scanning electron microscopy (HR-SEM) field emission transmission electron microscopy (FE-TEM), X-ray photoelectron spectroscopy (XPS), diffused reflectance (DRS) and photoluminescence (PL) spectroscopy. The results suggested that rare earth tungstate doping, with Dy2WO6, on ZnO has a great influence on the photocatalytic activity. Dy2WO6-ZnO possesses high reusability without appreciable loss of catalytic activity up to four runs and exhibits higher electrocatalytic activity than the prepared ZnO for methanol electrooxidation in alkaline medium, revealing its promising potential as the anode catalyst in direct methanol fuel cells. Hydrophobicity of ZnO increases on doping with Dy2WO6.
01 Feb 2017
TL;DR: In this paper, undoped and Ce doped ZnO nanorods were synthesized on ITO coated glass substrates by ultrasonic spray pyrolysis for seeding deposition and hydrothermal methods at a temperature of 95 0C for 2 hours for growth.
Abstract: Zinc oxide (ZnO) is a n-type semiconductor material which has a wide direct band gap energy of ~ 3.3 eV, and other interesting optical properties, hence it's potentially applied to various fields such as electronics, optoelectronics, sensors, photonic devices, and also photocatalyst. Dopant in ZnO nanostructures is an effective way to improve ZnO's structural properties in various applications. In this study, undoped and Ce doped ZnO nanorods were synthesized on ITO coated glass substrates by ultrasonic spray pyrolysis for seeding deposition and hydrothermal methods at a temperature of 95 0C for 2 hours for growth. X-ray diffraction, field emission scanning electron microscopy (FESEM), UV-VIS and Photoluminescence spectroscopy were used to characterize the crystal structure, surface morphology and optical properties of ZnO nanorods and the photocatalytic activity test for methylene blue degradation. The experimental results showed that 3% Cerium dopant has produced hexagonal morphology ZnO nanorod growing more uniform on (002) crystal planes, increased the intensity of ultraviolet absorbance thereby increase the degradation speed of methylene blue.