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Showing papers on "Field electron emission published in 2013"


Journal ArticleDOI
TL;DR: First-principles density functional calculations suggest that the enhanced field emission may also be due to an overalp of the electronic structures of WS2 and RGO, where graphene-like states are dumped in the region of the WS2 fundamental gap.
Abstract: We report here the field emission studies of a layered WS2-RGO composite at the base pressure of ~1 × 10−8 mbar. The turn on field required to draw a field emission current density of 1 μA/cm2 is found to be 3.5, 2.3 and 2 V/μm for WS2, RGO and the WS2-RGO composite respectively. The enhanced field emission behavior observed for the WS2-RGO nanocomposite is attributed to a high field enhancement factor of 2978, which is associated with the surface protrusions of the single-to-few layer thick sheets of the nanocomposite. The highest current density of ~800 μA/cm2 is drawn at an applied field of 4.1 V/μm from a few layers of the WS2-RGO nanocomposite. Furthermore, first-principles density functional calculations suggest that the enhanced field emission may also be due to an overalp of the electronic structures of WS2 and RGO, where graphene-like states are dumped in the region of the WS2 fundamental gap.

211 citations


Journal ArticleDOI
26 Aug 2013-Small
TL;DR: Owing to the low turn-on field and planar (sheetlike) structure, the MoS₂ could be utilized for future vacuum microelectronics/nanoelectronic and flat panel display applications.
Abstract: Field emission studies are reported for the first time on layered MoS₂ sheets at the base pressure of ∼1 × 10⁻⁸ mbar. The turn-on field required to draw a field emission current density of 10 μA/cm² is found to be 3.5 V/μm for MoS₂ sheets. The turn-on values are found to be significantly lower than the reported MoS₂ nanoflowers, graphene, and carbon nanotube-based field emitters due to the high field enhancement factor (∼1138) associated with nanometric sharp edges of MoS₂ sheet emitter surface. The emission current-time plots show good stability over a period of 3 h. Owing to the low turn-on field and planar (sheetlike) structure, the MoS₂ could be utilized for future vacuum microelectronics/nanoelectronic and flat panel display applications.

201 citations


Journal ArticleDOI
16 Jun 2013
TL;DR: An alternative tunneling process is considered, that is, the well-known Fowler-Nordheim (FN) tunneling that occurs at high electric fields, and this new approach relaxes the requirements on gap dimensions, and intuitively suggests that with a sufficiently high-intensity irradiation, the CTP can be excited via FN tunneling for a range of subnanometer gaps.
Abstract: Summary form only given. A plasmon resonant mode is the collective oscillation of free electrons in a structure stimulated by incident light. Reducing the gap between two metal nanoparticles down to atomic dimensions uncovers novel plasmon resonant modes. Of particular interest is a mode known as the charge transfer plasmon (CTP). This mode has been experimentally observed in touching nanoparticles, where charges can shuttle between the nanoparticles via a conductive path. However, the CTP mode for nearly touching nanoparticles has only been predicted theoretically to occur via direct tunneling when the gap is reduced to ~0.4 nm2. Because of challenges in fabricating and characterizing gaps at these dimensions, experiments have been unable to provide evidence for this plasmon mode that is supported by tunneling. In this work, we consider an alternative tunneling process, that is, the well-known Fowler-Nordheim (FN) tunneling that occurs at high electric fields, and apply it for the first time in the theoretical investigation of plasmon resonances between nearly touching nanoparticles. This new approach relaxes the requirements on gap dimensions, and intuitively suggests that with a sufficiently high-intensity irradiation, the CTP can be excited via FN tunneling for a range of subnanometer gaps. For instance, a plasmonic gap field of 1010 V/m (or an incident power of 3×1010 W/cm2) is needed when the gap length is 0.8 nm. The unique feature of FN tunneling induced CTP is the ability to turn on and off the charge transfer by varying the intensity of an external light source, and this could inspire the development of novel quantum devices, such as high speed switches and modulators.

124 citations


Journal ArticleDOI
TL;DR: The fabrication of a fully vacuum-sealed compact x-ray tube based on focused carbon nanotube (CNT) field-emission electrons for various radiography applications showed a stable and reliable operation, indicating good maintenance of a vacuum level of below 5 × 10(-6) Torr and the possibility of field- Emission x-rays tubes in a stand-alone device without an active pumping system.
Abstract: We report on a fully vacuum-sealed compact x-ray tube based on focused carbon nanotube (CNT) field-emission electrons for various radiography applications. The specially designed two-step brazing process enabled us to accomplish a good vacuum level for the stable and reliable operation of the x-ray tube without any active vacuum pump. Also, the integrated focusing electrodes in the field-emission electron gun focused electron beams from the CNT emitters onto the anode target effectively, giving a small focal spot of around 0.3 mm with a large current of above 50 mA. The active-current control through the cathode electrode of the x-ray tube led a fast digital modulation of x-ray dose with a low voltage of below 5 V. The fabricated compact x-ray tube showed a stable and reliable operation, indicating good maintenance of a vacuum level of below 5 × 10(-6) Torr and the possibility of field-emission x-ray tubes in a stand-alone device without an active pumping system.

104 citations


Journal ArticleDOI
TL;DR: The orthodox emission hypothesis is a set of physical and mathematical assumptions that permit well-specified analysis of measured currentvoltage data relating to field electron emission (FE) as mentioned in this paper, and it is based on the assumption that the electron emission is caused by a single electron.
Abstract: The orthodox emission hypothesis is a set of physical and mathematical assumptions that permit well-specified analysis of measured currentvoltage data relating to field electron emission (FE). If t...

86 citations


Journal ArticleDOI
TL;DR: The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed and the development of the optimization procedure for CNT array in Terms of the maximum reachable emission current density was developed.
Abstract: Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules.

85 citations


Journal ArticleDOI
12 Nov 2013-ACS Nano
TL;DR: It is observed that these films could be used as electron field emission sources with extraordinary efficiencies; threshold electric field of ca.
Abstract: We report the preparation of hybrid paperlike films consisting of alternating layers of graphene (or graphene oxide) and different types of multiwalled carbon nanotubes (N-doped MWNTs, B-doped MWNTs, and pristine MWNTs). We used an efficient self-assembly method in which nanotubes were functionalized with cationic polyelectrolytes in order to make them dispersible in water, and subsequently these suspensions were mixed with graphene oxide (GO) suspensions, and the films were formed by casting/evaporation processes. The electronic properties of these films (as produced and thermally reduced) were characterized, and we found electrical resistivities as low as 3 × 10–4 Ω cm. Furthermore, we observed that these films could be used as electron field emission sources with extraordinary efficiencies; threshold electric field of ca. 0.55 V/μm, β factor as high as of 15.19 × 103, and operating currents up to 220 μA. These values are significantly enhanced when compared to previous reports in the literature for oth...

83 citations


Journal ArticleDOI
TL;DR: The as-prepared phosphors might be promising for use in field-emission display (FED) devices and the cathodoluminescence properties of SrY2O4: Tb(3+)/Tm(3 +)/Dy(3+) phosphors including the dependence of CL intensity on accelerating voltage and filament current, the decay behaviour of CLintensity under electron bombardment, and the stability of CIE chromaticity coordinate have been investigated in detail.
Abstract: Tb3+, Tm3+, and Dy3+-activated SrY2O4 phosphors have been prepared via Pechini-type sol–gel method. X-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) and lifetimes, as well as cathodoluminescence (CL) spectra were used to characterize the samples. Under low-voltage electron beam excitation, the Tb3+-doped samples show a green luminescence, with a better CIE coordinates and higher emission intensity than the commercial product ZnO: Zn. Blue and yellow emissions could be obtained by doping with Tm3+ and Dy3+, respectively. A color-tunable emission in SrY2O4 phosphors can be realized by co-doping with Tm3+ and Dy3+. White cathodoluminescence (CL) has been realized in a single-phase SrY2O4 host by co-doping with Tm3+ and Dy3+ for the first time with CIE (0.315, 0.333). Furthermore, the cathodoluminescence (CL) properties of SrY2O4: Tb3+/Tm3+/Dy3+ phosphors including the dependence of CL intensity on accelerating voltage and filament current, the decay behaviour of CL intensity under electron bombardment, and the stability of CIE chromaticity coordinate have been investigated in detail. The as-prepared phosphors might be promising for use in field-emission display (FED) devices.

82 citations


Journal ArticleDOI
TL;DR: In this paper, a digital miniature x-ray tube with a high-density triode carbon nanotube (CNT) field emitter was fabricated for special xray applications, which exhibited stable and reliable operation over 250 h in a pulse mode at an anode voltage of above 25 kV.
Abstract: We have fabricated a digital miniature x-ray tube (6 mm in diameter and 32 mm in length) with a high-density triode carbon nanotube (CNT) field emitter for special x-ray applications. The triode CNT emitter was densely formed within a diameter of below 4 mm with the focusing-functional gate. The brazing process enables us to obtain and maintain a desired vacuum level for the reliable electron emission from the CNT emitters after the vacuum packaging. The miniature x-ray tube exhibited a stable and reliable operation over 250 h in a pulse mode at an anode voltage of above 25 kV.

73 citations


Journal ArticleDOI
TL;DR: In this paper, the response of the electronic properties of graphene wrinkles to charge injecting and external electric field, which is closely related to field emission properties, has been extensively studied by first-principles calculations.
Abstract: Wrinkles can be seen as a kind of protrusion formed on the surface of graphene sheets. The response of the electronic properties of graphene wrinkles to charge injecting and external electric field, which is closely related to field emission properties, has been extensively studied by our first-principles calculations. We find that increasing the wrinkle size and its top curvature not only improves the field enhancement factor of the wrinkled graphene but also decreases the electron affinities and ionization potentials. When injecting charges, both the charge accumulation and depletion mostly distribute at the top parts of the wrinkles and become more concentrated in the wrinkle with a higher curvature. The change of the highest occupied molecular orbital and the lowest unoccupied molecular orbital caused by electric field mainly locates at the wrinkled parts, especially at its top. These results demonstrate that wrinkled graphene could be a good candidate for field emitter.

73 citations


Journal ArticleDOI
TL;DR: Field-emission tests of this new composite material show the typical low threshold voltages for carbon nanotube structures but with greatly increased emission current, better stability, and longer lifetime.
Abstract: A thin diamond-like carbon (DLC) film was deposited onto ad ensely packed"forest" of vertically aligned multiwalled carbon nanotubes (VACNT). DLC deposition caused the tips of the CNTs to clump together to form a microstructured surface. Field-emission tests of this new composite material show the typical low threshold voltages for carbon nanotube structures (2 V μm −1 ) but with greatly increased emission current, better stability, and longer lifetime.

Journal ArticleDOI
TL;DR: In this article, the growth of flexible SiC quasialigned nanoarrays with N dopants on carbon fabric substrate via the catalyst-assisted pyrolysis of a polymeric precursor was reported.
Abstract: In the present work, we report the growth of flexible SiC quasialigned nanoarrays with N dopants on carbon fabric substrate via the catalyst-assisted pyrolysis of a polymeric precursor. The resultant products are systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS). The as-synthesized SiC nanowires are single-crystalline and grow along the [111] direction with a uniform spatial distribution of N dopants. The effect of the distance between the SiC array and the anode on the Field emission (FE) properties was investigated. FE measurements show that these N-doped SiC nanoarrays could be an excellent candidate for field emitters with very low turn-on fields of 1.90–2.65 V μm−1 and threshold fields of 2.53–3.51 V μm−1, respectively, which can be mainly attributed to the decrease of work function induced by the N dopants.

Journal ArticleDOI
TL;DR: In this paper, the morphologies, structures and temperature-dependent field emission (FE) properties of 1D lanthanum hexaboride (LaB6) nanowire arrays were systematically investigated.
Abstract: High-quality, uniform, one-dimensional (1D) lanthanum hexaboride (LaB6) nanostructures with different morphologies (for example, sparse or dense nanoneedles, or nanorods and nanowire arrays) were fabricated through an effective, easily controlled, one-step, catalyst-free chemical vapor deposition process. The morphologies, structures and temperature-dependent field emission (FE) properties were systematically investigated. FE measurements at room temperature (RT) showed that LaB6 nanowire arrays possess the best FE characteristics among all 1D LaB6 nanostructures, with a low turn-on electric field (Eto, 1.82 V μm−1), a low threshold electric field (Ethr, 2.48 V μm−1), a high current (5.66 mA cm−2 at 2.92 V μm−1) and good stability (at a testing time of 1000 min, fluctuations were <6.0%). Temperature-dependent FE showed that the turn-on and threshold electric fields decreased from 1.82 to 1.06 and 2.48 to 1.62 V μm−1, respectively, whereas the emission current density increased significantly from 0.20 to 9.05 mA cm−2 at 2.20 V μm−1 when the temperature was increased from RT to 723 K. The emission current density and the dependence of the effective work function on temperature were also investigated. We attribute the significant reduction of the turn-on and threshold fields and the remarkable increase of emission current to a decrease in the effective work function with temperature

Journal ArticleDOI
TL;DR: By utilizing a nanometer ultrafast electron source in a point projection microscope, it is demonstrated that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained.
Abstract: By utilizing a nanometer ultrafast electron source in a point projection microscope we demonstrate that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained. The duration of the emission process of the photoemitted electrons used to make images is shown to be of the order of 100 fs using an autocorrelation technique. The compact geometry of this photoelectron point projection microscope does not preclude its use as a simple ultrafast electron microscope, and we use simple analytic models to estimate temporal resolutions that can be expected when using it as a pump-probe ultrafast electron microscope. These models show a significant increase in temporal resolution when comparing to ultrafast electron microscopes based on conventional designs. We also model the microscopes spectroscopic abilities to capture ultrafast phenomena such as the photon induced near field effect.

Journal ArticleDOI
22 Jan 2013-ACS Nano
TL;DR: It is shown that there is an optimum thickness of STO coatings to effectively reduce the work function of CNTs and yet minimize the tunneling width for electron emissions, and simulation and modeling suggest that PMMA-STO-CNT matrices have suppressed screening effects and Coulombs' repulsion forces between electrons in adjacent C NTs, leading to low emission threshold, high emission density, and prolonged emission stability.
Abstract: Novel PMMA–STO–CNT matrices were created by opened-tip vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) with conformal coatings of strontium titanate (STO) and poly(methyl methacrylate) (PMMA). Emission threshold of 0.8 V/μm was demonstrated, about 5-fold lower than that of the as-grown VA-MWCNTs. This was obtained after considering the related band structures under the perspective of work functions and tunneling width as a function of the STO thickness. We showed that there is an optimum thickness of STO coatings to effectively reduce the work function of CNTs and yet minimize the tunneling width for electron emissions. Furthermore, simulation and modeling suggest that PMMA–STO–CNT matrices have suppressed screening effects and Coulombs’ repulsion forces between electrons in adjacent CNTs, leading to low emission threshold, high emission density, and prolonged emission stability. These findings are important for practical application of VA-MWCNTs in field emission devices, X-ray generation, an...

Journal ArticleDOI
TL;DR: In this article, a hierarchical three-dimensional (3D) Cu2S@ZnO heteroarchitecture was successfully synthesized by a facile three-step synthetic process.
Abstract: A novel hierarchical three-dimensional (3D) Cu2S@ZnO heteroarchitecture was successfully synthesized by a facile three-step synthetic process. FESEM and TEM analyses revealed the formation of the hierarchical 3D structure of the as-prepared Cu2S@ZnO. The purity and crystalline phase of the individual component in the 3D Cu2S@ZnO were determined by a powder X-ray diffractogram. The formation of the hierarchical 3D structure of the as-prepared Cu2S@ZnO leads to multiple p–n junctions formed at p-Cu2S@n-ZnO interfaces, which promote the generation and separation of photoinduced electrons and holes and thus improves the photocatalytic efficiency tremendously. According to the data, after irradiation for 40 min, the remaining MB in solution is about 35% for Cu2S nanoflowers and 9% for Cu2S@ZnO binary nanoflowers. Also, the increases in the overall aspect ratio and the ZnO nanoparticles act as extra emission sites, which help to enhance the field emission properties. The turn-on fields and threshold fields for the Cu2S nanoflowers as well as the Cu2S@ZnO nanoflower hybrid emitters are 3.3 and 9.2 V μm−1, 2 and 6.3 V μm−1, respectively. Compared with the Cu2S nanoflowers, the Cu2S@ZnO hetero-nanoflowers show excellent improvements in both photocatalytic and field emission applications.

Journal ArticleDOI
TL;DR: In this paper, high-quality NdB6 nanostructures with a low work function are successfully synthesized via an one-step catalyst-free chemical vapor deposition process, and the nanoneedles with sharp tips demonstrate the lowest turn-on (2.71 V/μm) and threshold (3.60 V/mm) electric fields, as well as a high current density (5.37 mA/cm2) at a field of 4.32 V/m).
Abstract: High-quality NdB6 nanostructures with a low work function are successfully synthesized via an one-step catalyst-free chemical vapor deposition process. Field emission properties of these nanostructures (curve nanowires, short-straight nanorods, long-straight nanowires, and nanoneedles) are systematically investigated and found to be strongly affected by the tip morphologies and temperatures. The nanoneedles with sharp tips demonstrate the lowest turn-on (2.71 V/μm) and threshold (3.60 V/μm) electric fields, as well as a high current density (5.37 mA/cm2) at a field of 4.32 V/μm in comparision with other nanostructures. Furthermore, with an increase in temperature from room temperature to 623 K, the turn-on field of the nanoneedles decreases from 2.71 to 1.76 V/μm, and the threshold field decreases from 3.60 to 2.57 V/μm. Such excellent performances make NdB6 nanomaterials promising candidates for application in flat panel displays and nanoelectronics building blocks.

Journal ArticleDOI
01 Jul 2013-Carbon
TL;DR: In this article, double-walled carbon nanotubes (DWCNTs) have been synthesized by direct current arc discharge in low pressure air using a mixture of Fe catalyst and FeS promoter.

Journal ArticleDOI
TL;DR: The controlled growth of highly ordered and well aligned one-dimensional tellurium nanostructure arrays are reported via a one-step catalyst-free physical vapor deposition method and opens up new means for their potential applications in electronic devices and displays.
Abstract: We report the controlled growth of highly ordered and well aligned one-dimensional tellurium nanostructure arrays via a one-step catalyst-free physical vapor deposition method. The density, size and fine structures of tellurium nanowires are systematically studied and optimized. Field emission measurement was performed to display notable dependence on nanostructure morphologies. The ordered nanowire array based field emitter has a turn-on field as low as 3.27 V μm−1 and a higher field enhancement factor of 3270. Our finding offers the possibility of controlling the growth of tellurium nanowire arrays and opens up new means for their potential applications in electronic devices and displays.

Journal ArticleDOI
TL;DR: In this paper, the authors reported the growth of quasi-aligned, single-crystalline n-type doped (N-doped) 3C-SiC nanoneedles on highly flexible carbon fabric via the catalyst assisted pyrolysis of polysilazane.
Abstract: Flexible field emission (FE) arrays have a wide range of applications in next generation low-cost, lightweight and wearable electronics, roll-up displays, and large-area circuits on curved objects, yet the growth of tapered, high-quality single-crystalline nanostructure-based emitters on flexible substrates with superior FE properties remains challenging and related work is limited. On the other hand, our recent studies have shown that silicon carbide (SiC) 1D nanostructures could meet nearly any stringent requirement for an ideal FE emitter. In this contribution, we report the growth of quasi-aligned, single-crystalline n-type doped (N-doped) 3C-SiC nanoneedles (3C-SiCNNs) on highly flexible carbon fabric via the catalyst assisted pyrolysis of polysilazane. The as-synthesized SiCNNs possess a tapered structure with tiny clear tips with sizes of several to tens of nanometers. The fabricated 3C-SiCNNs have extremely low emission turn-on fields (Eon) in the range of 0.5–1.6 V μm−1 with an average of 1.1 V μm−1, which is comparable to the lowest value ever reported for 1D nanostructure emitters that, however, are grown on rigid substrates. Specifically, our SiCNN arrays on carbon fabric are mechanically and electrically robust, and can withstand mechanical bending up to 500 times and still retain excellent FE performance with Eon of ∼1.1 V μm−1. The field-enhancement factor has been calculated to be 6.5 × 103. The superior FE properties can be attributed to the significant enhancements of the tapered unique morphology and N-doping of the SiCNNs. Calculations based on local density functional theory suggest that nitrogen dopants in the 3C-SiC nanostructure could favor a more localized impurity state near the conduction band edge, which improves the electron field emission. We strongly believe that the present work will provide a new insight into the fabrication of flexible field emission arrays with ultralow turn-on fields enhanced by both shape and doping.

Journal ArticleDOI
01 Aug 2013-Vacuum
TL;DR: In this article, the organic layer anchoring the vertical graphene sheets acted as negative feedback layer, which contributed to the high uniformity and stability of the field emission device and paved the low-cost way for applications of graphenes in large-scale field emission devices.

Journal ArticleDOI
01 Feb 2013-Carbon
TL;DR: In this paper, the authors modified vertically aligned multiwalled carbon nanotubes (MWCNTs) grown on a Cu substrate by NH 3 direct current plasma treatment for varying durations and investigated their microstructure and field emission properties.

Journal ArticleDOI
TL;DR: In this article, the breakdown voltage curves in argon discharges with parallel-plane electrodes separated from 1 to 100 µm were used to estimate the effective yield of the secondary electron emission in microgaps.
Abstract: This paper contains results of experimental and simulation studies of the direct-current breakdown voltage curves in argon discharges with parallel-plane electrodes separated from 1 to 100 µm. The negative slope of the Fowler–Nordheim plot indicates that the current flow is due to field-emitted electrons. Based on the breakdown voltage curves, the effective yield has been estimated. The secondary electron emission in microgaps depends primarily on the electric field E rather than reduced electric field E/N, leading directly to the violation of Paschen's law. The obtained results provide better insight into the role of the enhancement of the secondary electron emission due to high electric field generated in microgaps. Due to the lack of experimental data in microgaps, there are only a few values for the effective yield and no value for argon. By fitting presented experimental data, realistic values of the effective yield in microgaps are obtained and used for the calculations of the breakdown voltages representing basic design data of high-voltage equipment.

Journal ArticleDOI
TL;DR: Modifications to the structure of the DLC films through promotion of metal-induced sp2 bonding and the introduction of surface asperities significantly reduce the value of the threshold field, which can lead to the next-generation, large-area simple and inexpensive field emission devices.
Abstract: A simple approach is proposed for obtaining low threshold field electron emission from large area diamond-like carbon (DLC) thin films by sandwiching either Ag dots or a thin Ag layer between DLC and nitrogen-containing DLC films. The introduction of silver and nitrogen is found to reduce the threshold field for emission to under 6 V/μm representing a near 46% reduction when compared with unmodified films. The reduction in the threshold field is correlated with the morphology, microstructure, interface, and bonding environment of the films. We find modifications to the structure of the DLC films through promotion of metal-induced sp2 bonding and the introduction of surface asperities, which significantly reduce the value of the threshold field. This can lead to the next-generation, large-area simple and inexpensive field emission devices.

Journal ArticleDOI
TL;DR: In this article, a well-aligned SiC nanowire array is successfully synthesized on carbon cloth by a facile chemical vapor deposition without using any templates, and the resulting SiC arrays acting as cold electron emitters exhibit excellent field emission performance with very low turn-on and threshold voltages of 1.3 and 2.2

Journal ArticleDOI
TL;DR: The evaporation mechanisms of surface atoms in laser assisted atom probe tomography (LA-APT) are reviewed with an emphasis on the changes in laser-matter interaction when the sample is a nanometric tip submitted to a high electric field.

Journal ArticleDOI
TL;DR: In this paper, the impact of the edges and the presence of dopants to the work function (WF) of graphene nanoribbons and nanoflakes was studied by an ab initio approach.
Abstract: The impact of the edges and the presence of dopants to the work function (WF) of graphene nanoribbons (GNR) and nanoflakes was studied by an ab initio approach. The strong dependence of the WF upon the GNR structure was found and a promising character for the field emission by the donor type impurities was observed. Basing on the predominant impact of the nanostructure edges to the emission properties, the small graphene flakes were investigated as a possible source for the electron emission. The obtained weak dependence of the low WF values of the graphene flakes on their size and shape allows to suggest that the pure carbon medium with high and uniform emission properties can be fabricated by today's technology.

Journal ArticleDOI
TL;DR: In this paper, the authors compared the temperature-dependent and electric-field-dependent Raman spectra of graphene oxide and found that the evolutions of Raman spectrum are not in agreement with each other, except the intensity of the G peak that decreases in both cases.
Abstract: Electric-field-dependent in situ Raman studies have been carried out on chemically prepared graphene oxide. The Raman spectra show significant changes with increase in the applied electric field; in particular, the intensity of the G peak decreases with electric field. This behavior is typical for chemically or thermally reduced graphene oxide. To understand the nature of reduction, we compared the temperature-dependent and electric-field-dependent Raman spectra of graphene oxide and found that the evolutions of Raman spectra are not in agreement with each other, except the intensity of the G peak that decreases in both cases. The D peak broadens significantly with increase in temperature, whereas it sharpens in the case of applied electric field. The electron-field-emission properties of the electrically reduced graphene oxide were also carried out, and the turn-on field was found to be 9.1 V/μm.

Journal ArticleDOI
TL;DR: A new type of cold cathode field emission electron source capable of extremely high emission, producing current densities at levels comparable to thermal sources is reported on.
Abstract: We report on a new type of stable field emitter capable of electron emission at levels comparable to thermal sources. Such an emitter potentially enables significant advances in several important technologies which currently use thermal electron sources. These include communications through microwave electronics, and more notably imaging for medicine and security where new modalities of detection may arise due to variable-geometry x-ray sources. Stable emission of 6 A cm−2 is demonstrated in a macroscopic array, and lifetime measurements indicate these new emitters are sufficiently robust to be considered for realistic implementation. The emitter is a monolithic structure, and is made in a room-temperature process. It is fabricated from a silicon carbide wafer, which is formed into a highly porous structure resembling an aerogel, and further patterned into an array. The emission properties may be tuned both through control of the nanoscale morphology and the macroscopic shape of the emitter array.

Journal ArticleDOI
Kaimo Deng1, Hao Lu1, Zhiwei Shi1, Qiong Liu1, Liang Li1 
TL;DR: Results indicate that the flexible three-dimensional SnO2 nanowire arrays can be used as functional building blocks for efficient photodetectors and field emitters.
Abstract: Flexible three-dimensional SnO2 nanowire arrays were synthesized on a carbon cloth template in combination with atomic layer deposition and vapor transport. The as-grown nanostructures were assembled by high density quasi-aligned nanowires with a large aspect ratio. Nanoscale photodetectors based on the flexible nanostructure demonstrate excellent ultraviolet light selectivity, a high speed response time less than 0.3 s, and dark current as low as 2.3 pA. Besides, field emission measurements of the hierarchical structure show a rather low turn-on field (3.3 Vμm–1) and threshold field (4.5 Vμm–1), as well as an excellent field enhancment factor (2375) with a long-term stability up to 20 h. These results indicate that the flexible three-dimensional SnO2 nanowire arrays can be used as functional building blocks for efficient photodetectors and field emitters.