Electron Field Emission Properties Research Articles

Controlled growth of CuO nanowires on Cu grid via thermal oxidation process with enhanced field electron emission properties

Controlled growth of CuO nanowires on Cu grid via thermal oxidation process with enhanced field electron emission properties

One-dimensional diamond nanostructures: Fabrication, properties and applications

Diamonds exhibit a unique combination of numerous excellent physical and chemical properties, such as the highest hardness, high Young's modulus, wide bandgap, high carrier mobility, negative electron affinity, and high thermal conductivity. Especially, diamond has attracted significant attention in recent years for its outstanding performance in high-frequency and high-power electronic devices and thermal management. Inheriting the intrinsic physical and chemical properties of diamonds, one-dimensional (1D) diamond nanostructures exhibit many additional properties that are unavailable for bulk diamond or thin films, e.g., large specific surface area, ultrahigh elasticity, and some plasticity, tip effect as well as direct transport for photon or photo-induced carriers. These properties make 1D diamond nanostructures an ideal candidate for applications ranging from micro/nano-electromechanical systems (MEMS/NEMS) to field electron emission, optical, electrochemical, and biological areas. This review will first introduce the development of controlled synthesis methods of 1D diamond nanostructure, including bottom-up chemical vapor deposition growth and top-down selective etching of bulk diamond. Subsequently, we will summarize recent advances in the mechanical, electron field emission, optical, and biological properties of 1D diamond nanostructures and their applications in electron and photon emitter, MEMS, sensing, intracellular delivery, etc.

Diamond Nanostructures at Different Dimensions: Synthesis and Applications

AbstractDiamond materials at different nanoscales provide them various characteristics such as elastic mechanical properties in needle‐like nanotips, flexibility of 2D films having atomic thicknesses and constant hardness under high pressures, superior field electron emission properties of vertically wall‐like composites, unprecedented hardness and improved toughness of nanotwin diamond (nt‐diamond), while the inherent excellent properties of bulk diamond (e.g., high Young's modulus, robustness, biocompatibility) can be maintained. In this paper, the newly born 1D diamond nanothreads, 2D diamanes, as well as 3D nt‐diamond are briefly reviewed. The innovations, progresses and achievements of different dimensional diamond nanostructures, covering lines, planes and volumes are overviewed. The topical problems and future outlooks of diamond nanostructures are outlined and discussed.

Improved field emission properties of reduced graphene oxide decorated with indium nanoparticles

Low work function metals decoration of graphene is a effective method for the improvement of electron field emission properties. Indium, a relatively lower work function metal, is used to decorate reduced graphene oxide (RGO) films for the first time by simple and efficient solution process combined with magnetron sputtering method and the field emission properties are investigated. At continue voltage mode, the indium decorated RGO films display lower turn-on and threshold field as well as better emission stability than those of pristine RGO films. Moreover, the field emission performance of indium decorated RGO films is affected by the spacing between the cathode and anode. At pulse voltage mode, the indium decorated RGO films show approximately 10 times higher maximum emission current density compared to that at continue voltage mode. The calculation results by density functional theory indicate that the indium decoration of RGO significantly increases the density of states (DOS) near Fermi level and reduces the work function.

Self-consistent numerical solution of quantum regime with exchange-correlation effects of space charges for electron field emission in a nano-gap

The quantum effects of space charge on electron field emission have been widely investigated since the last century. When electrons energy and their mean spacing approach the Hartree level and the de Broglie wavelength respectively, the influence of the quantum effects on the field emission current becomes significant. In this work, by developing an in-house software, we self-consistently solve the one-dimensional Poisson-Schrödinger equation together with the Wentzel-Kramers-Brillouin-Jeffreys (WKBJ) model for metal-vacuum-metal nanogaps, after considering the anode screening effect, space charge Coulomb potential and exchange-correlation effects simultaneously. Employing the method, the electron field emission characteristics were studied by varying the nanogap spacing (D) and the electric field strength (F), and four different emission regimes including quantum regime (QR), space charge limited regime (SCLR), direct tunnelling regime (DTR) and field emission regime (FER) are defined. The influences of space charge field components on the field emission characteristics and space charge distribution are analyzed for different emission regimes in nanogap. In addition, the impact of using different exchange-correlation functionals (LDA, GGA and meta-GGA) on Jacob’s ladder for describing the quantum effects of space charge on the electron emission current density was analyzed. Finally, electron field emission properties of one-dimensional (1-D) nanogaps consisting of refractory metals (W and Mo) as well as the three-dimensional (3-D) nano-tip are discussed to elucidate the impact of the exchange-correlation effects on the enhanced field emission process at nanoscale.

Postannealing Temperature Effects on the Etching Behavior and Field Emission Properties of Cu‐Implanted Diamond

To investigate the postannealing temperature effects on the surface etching behavior and electron field emission (EFE) properties of the Cu‐implanted microcrystalline diamond (MCD) films, they are subjected to furnace annealing in a temperature range of 600–900 °C under N2 atmosphere at a rapid annealing rate. The etching behavior happens when the samples are annealed at 700 °C and above. The EFE performances enhance first and then decrease with the increasing annealing temperature. The optimum EFE property with a low turn‐on field of 6.42 V μm−1 is obtained after the Cu‐implanted MCD film is annealed at 700 °C. The enhancement in EFE properties originates from the presence of nanographitic phase and the formation of electron‐rich Cu nanoparticles, which encourage a higher efficient electron transport. In contrast, the structural studies reveal that when the samples annealed at 800 °C and above, Cu nanoparticles evaporate from the diamond surface and the sp2‐bonded carbon decomposes. Consequently, etch pits appear on the surface of the MCD sample. Moreover, it demonstrates that graphitization is the dominant mechanism of the diamond surface etching behavior and the enhancing of EFE properties.

The effects of Ar + N2 plasma power-based attachment of metal nanoparticles on the electron field emission properties of carbon nanotubes

An ideal vacuum-based electron emitter requires a low turn-on field and quick emission processes. Carbon nanotubes (CNTs) have great potential for emission applications, but have some limitations that affect their performance. Consequently, they can benefit from the alteration of their surface morphology upon decoration with plasma-based metal nanoparticles. In this work, we have attached iron nanoparticles on the CNTs surface via a radio frequency (rf) sputtering process using Ar + N2 gas with various plasma power in steps of 50 W. Field emission scanning electron microscopy (FESEM) micrographs have confirmed the attachment of the iron nanoparticles and etching of the nanotubes surface at high plasma power. The Raman spectra strongly confirm the formation of defects in the carbon sheet of the nanotubes. In the plasma treatment process, the increase in the Dband intensity enhanced the degree of disorder and may be beneficial for enhanced emission properties. The field electron emission properties are significantly enhanced after the Fe nanoparticles attached with plasma incorporated in terms of the reduction in Eto (1.64 from 2.02 V/μm) &Eth (1.98 from 2.64 V/μm), and increase in J (391.11–1179.24 μA/cm2) and β (1419–2900), respectively. The field emission parameters of the field emitters are modified due to incorporation of nitrogen species, attached Fe nanoparticles, and reduction in the nanotube density. The as-prepared field emitters also qualified the orthodox field emission hypothesis test by exhibiting fextr values in an acceptable range. Therefore, we can use the Ar + N2 plasma-based Fe nanoparticles decorated CNT field emitters in vacuum electronic device applications.

Influence of power-dependent Argon gas plasma treatment on the electron field emission properties of carbon nanotube field-emitters

Influence of power-dependent Argon gas plasma treatment on the electron field emission properties of carbon nanotube field-emitters

Plasma Post‐Treatment Process‐Induced Grain Coalescence to Improve the Electron Field‐Emission Properties of Ultrananocrystalline Diamond Films

Plasma post‐treatment (PPT) process is an effective way to improve the electron field‐emission (EFE) properties of microwave plasma chemical vapor deposited ultrananocrystalline diamond (MP‐UNCD) films, while its effects on hot‐filament chemical vapor deposited UNCD (HF‐UNCD) films were not confirmed. Due to monodispersed Ta atoms existing in HF‐UNCD films, PPT process shows different effects on the structure evolution and EFE properties of HF‐UNCD films and MP‐UNCD films. CH4/N2 PPT process make diamond grains change from small spherical particles to large plate‐like aggregates with lots of stacking faults in HF‐UNCD films. This is ascribed to both the CN species in CH4/N2 plasma, which induces anisotropic growth of diamond and the monodispersed Ta atoms resulted in transition of graphite to diamond, which connect the neighboring nanosized diamond grains to a larger one and produce lots of stacking faults. The charges are easier to accumulate and emitted in the edges of the plate‐like diamond and stacking faults have lower negative electron affinity. These lower the turn‐on field from 26.3 to 12.7 V μm−1. It is different from that of MP‐UNCD films, in which only anisotropic growth occurs and forms needle‐like diamond due to CN species.

Photoelectron properties and enhanced field electron emission of cobalt ferrite-reduced graphene oxide nanocomposite

In the present report, field electron emission (FE) characteristics of cobalt ferrite (CF) nanoparticles (NPs) decorated on reduced graphene oxide (rGO) are studied. The rGO-CF nanocomposite was synthesized by simple glycol-based route. The formation of rGO-CF nanocomposite was confirmed using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). TEM results indicated the uniform decoration of CF NPs on the rGO sheet. The average particle size of decorated CF NPs is ∼8 nm. XPS results revealed the partial reduction of GO to rGO. The ultraviolet photoelectron spectroscopy (UPS) was utilized to calculate the work function of the nanocomposite and it was found to be ∼4.3 eV. The FE properties of rGO-CF nanocomposite were investigated in planer diode assembly. The nanocomposite showed excellent FE performance with low turn-on ∼ 1.34 V/μm and threshold field ∼ 1.72 V/μm values. The maximum current density was found to be 2.8 mA/cm2, at an applied field of 2.88 V/μm. This enhancement in FE characteristics was explained on the basis of surface morphology, increased number of emitting sites, high field enhancement factor, and reduction in the work function of the emitter. The FE results suggest that rGO-CF based emitters have the potential for the development of various micro-nano electronic devices.

Field Electron Emission from Crumpled CVD Graphene Patterns Printed via Laser-Induced Forward Transfer.

A new approach to the fabrication of graphene field emitters on a variety of substrates at room temperature and in an ambient environment is demonstrated. The required shape and orientation of the graphene flakes along the field are created by the blister-based laser-induced forward transfer of CVD high-quality single-layer graphene. The proposed technique allows the formation of emitting crumpled graphene patterns without losing the quality of the initially synthesized graphene, as shown by Raman spectroscopy. The electron field emission properties of crumpled graphene imprints 1 × 1 mm2 in size were studied. The transferred graphene flakes demonstrated good adhesion and emission characteristics.

Fabrication of rutile TiO2 nanoarrays/free-standing diamond composite film and its field emission properties

Highly aligned TiO2 nanoarrays (TNAs) are fabricated on free-standing diamond (FSD) films and Si wafers (for comparison). Different anodizing times (e.g., 5, 15, 25, 45, and 60 min) are used to investigate the morphologies of TNAs and their effect on the electron field emission (EFE) properties. With the increase of the anodizing time, the features of TNAs grown on the FSD film undergo the transition from nanorods to nanopores and then to nanotubes. The XRD, Raman, and TEM results reveal that TNAs synthesized on the FSD film are preferentially oriented rutile phase, while those synthesized on the Si wafers show the anatase structure. Rutile TiO2 has a relatively low work function and is favorable to EFE performance. Importantly, the nanotubes on the FSD substrate with a 45 min anodizing time grow perpendicularly to each crystal face of the diamond grains and exhibit a superior EFE behavior, which can be turned on at a low field of 0.7 V/μm and attain a high current density of 0.6 mA/cm2 at an applied field of 1.6 V/μm. The enhanced EFE performance of TNAs/FSD composite film is ascribed to the synergetic effects among the electron acceleration layer played by the FSD film, more electron emission sites provided by the nanotubes with large aspect ratios, and lower work function of rutile TiO2. Moreover, the heterogeneity of the FSD substrate and TNAs also can decrease the interface barrier to make electrons transmit effectively.

Significant enhancement in field emission and photoluminescence properties of vertically aligned tellurium nanorods by plasma treatment

Significant improvement in electron field emission (FE) properties of high density vertically aligned tellurium nanorods (TNRs) arrays has been observed by plasma treatment. At first the TNRs are grown by catalyst free chemical vapor deposition (CVD) method and are systematically characterized by FESEM, EDS, TEM, HRTEM, XRD and XPS. Later on TNRs were treated with plasma (Ar and N) and their effects on morphology, optical and FE properties are investigated comprehensively. The FE of TNRs containing 40–50 nm size have been enhanced from 6.22 Vμm−1 to 3.25 Vμm−1 which is more than 52%. This research reveals that plasma treatment has effectively modified the surface morphology (confirmed by TEM) and created sharp tips on TNRs which act as extra source of field emitters believed to contribute the enhancement of field emission. Plasma treated TNRs not only exhibited excellent FE properties (3.25 Vμm−1), these aligned TNRs also portrayed the tremendous stability with insignificant FE current fluctuation (<4%) for 60 min. Crucially, the reported FE turn-on value is low enough for their potential applications in device fabrications. So these findings offer the improvement in the field emission of TNRs by plasma treatment proposing their potential utilization in devices.

Study the electron field emission properties of silver nanoparticles decorated carbon nanotubes-based cold-cathode field emitters via post-plasma treatment

Study the electron field emission properties of silver nanoparticles decorated carbon nanotubes-based cold-cathode field emitters via post-plasma treatment

Time-dependent resonating plasma treatment of carbon nanotubes for enhancing the electron field emission properties

Time-dependent resonating plasma treatment of carbon nanotubes for enhancing the electron field emission properties

Investigation of changes in field electron emission characteristics of industrial fine-grained graphite when operated in an argon atmosphere up to 10–2 Pa

Studying of field electron emission properties of carbon cathodes operating under technical vacuum conditions is a promising scientific field. Massive cathode made of commercial fine-grained graphite of MG (Russian abbreviation) grade is being investigated. Experiments on obtaining current-voltage characteristics and long-term testing are being carried out. The emitter made of fine-grained graphite demonstrates good emission properties under technical vacuum conditions. Carbon cathode is capable of operating at pressures up to 2×10–2 Pa. Increased pressure in the vacuum chamber leads to deterioration of cathode emission properties. Electric field enhancement factors were calculated for all stages of studies. Analysis of experimental data demonstrates decrease in enhancement factor due to ion bombardment of cathode surface during exploitation. This results in higher electric field for operation of investigated graphite cold cathodes.

Impact of edge functionalization on electron field-emission characteristics of carbon nanotubes: A theoretical approach

A theoretical approach using first-principle calculations of the density of states (DOS) of functionalized carbon nanotubes (CNTs) is carried out to understand their enhanced electron field emission (FE) properties. The theoretical functionalization of CNTs is perceived using hydrogenation (H/O–H) and oxidation methods. In order to investigate the enhancement in the FE properties of functionalized CNTs, both single-walled carbon nanotubes (SWCNT) and double-walled carbon nanotubes (DWCNT) are studied. The work function is observed to be more decreased in case of zigzag SWCNT (φ = 3.32 for oxygenated SWCNT) as compared to others SWCNT. The dependence of DOS on zigzag/armchair edge functionalization has also been investigated to reveal the impact of DOS on FE. The observed results indicate that edge functionalization of CNTs leads to significant changes in the band structure, DOS, and work functions. The shifting of DOS away from the Fermi level and decrease in work function is evidenced owing to the reduction in the curvature effect of CNT. Also, due to enhanced DOS near the Fermi level, making them a better proposition for FE applications. Our calculations provide an in-depth insight into the functionalization mechanism to understand the enhanced FE properties from them.

Effect of ambient temperature and cathode-anode separation on electron field emission property of carbon nanofibers thin films

Carbon nanofibers (CNFs) thin films were prepared by using Radio frequency assisted plasma enhanced chemical vapor deposition (RF-PECVD) technique. Nickel thin films have been used for preparation of CNFs thin films, which stimulates the growth. The identification and confirmation of the graphitic phase of CNFs thin films were confirmed by using X-Ray Diffractometer. Nanostructure surface morphology of the CNFs thin films have been investigated by an Atomic Force Microscope, which reveals that the typical diameter of the CNFs was ∼ 180 nm with length of several micrometers. The electron field emission properties of CNFs thin films have been carried out for different cathode–anode separation and for various ambient temperatures. It was observed that with the extent of cathode–anode separation from 70 to 210 μm, the turn-on field was reduced to 3.5 V/μm from 4.4 V/μm respectively. Temperature dependent electron field emission measurement showed that the turn-on field was reduced to 2.3 V/μm from 4.2 V/μm, as ambient temperature of CNFs thin films was increased from 30 °C to 250 °C respectively. The field enhancement factor and turn-on field were calculated and demonstrate the electron emission procedure.

Preparation, superior field emission properties and first principles calculation of electronic structure of SiC nanowire arrays on Si substrate

It is a crucial item to develop an available, efficient and stable cathode material for the application of flat-panel display, vacuum micro-electronic device, electron source and related area/equipment. In this work, oriented single-crystalline SiC nanowires (SiCNW) arrays were successfully fabricated onto the Si (100) substrate according to an easy Ni-catalyst-assisted chemical vapor deposition (CVD) process. The systematical characterization results suggested that product growth was modulated via the vapor-liquid-solid (VLS) mechanism. As the promising member in the candidate cathodes, SiCNW arrays with superior current emission stability (~ ± 6.1%) displayed decreased turn-on field (1.26 V/μm) along with threshold field (1.83 V/μm) at the optimal spacing between anode and cathode (about 500 μm), suggesting their great application potential as field emitters in the future. The positive effect of the stacking faults on the electronic structure and field emission (FE) properties were investigated through first principles calculation using Vienna ab initio Simulation package (VASP) of density functional theory (DFT). Furthermore, a reasonable synergetic electronic transmission mechanism based on peculiar morphology and electronic band structure was proposed to explain the superior field emission performances.

Study the electron field emission properties of plasma-based reduction of graphene oxide (GO): An ex-situ plasma approach

Vacuum-based electron emission devices requires fast and low turn-on field processes. Graphene oxide (GO) can be a perfect candidate for field electron emission applications. In this work, we have prepared graphene oxide (GO) via modified Hummer's method and treated it with dense plasma of argon gas (Ar). The surface morphology of the prepared GO reveals the growth of the stacked-layer and large surface area flakes of GO. Raman spectra reveals the high defective growth of GO. The impurities in the GO are due to the incorporation of oxygen moieties. For enhancing the field emission properties, the GO thin films were treated with a dense plasma of Ar gas at 50, 100, 150 and 200 W. Raman spectra strongly indicates the removal of oxygen moieties and formation of defects and vacancies in the sheet of plasma-treated GO. The field emission properties drastically improved in the scenario of plasma-treated GO field emitters. The turn-on and threshold fields were reduced after plasma treatment in comparison with pristine GO field emitters. The reduction in the turn-on and threshold fields is due to the enhancement in the edge effects, protrusion formation and modification in structural properties. The emission current density was drastically enhanced in the 200 W plasma-treated GO field emitters. The emission stability test was performed for a 600 min at 3 V / μ m applied electric field. The stability was enhanced with plasma power and shows the minimum current fluctuation. The field enhancement factor also improved after plasma treatment and for 200 W treated β becomes 3 times the pristine GO. We have also implemented the orthodox emission hypothesis test, which was qualified by the prepared pristine and plasma-treated GO field emitters due to the f e x t r values belonging in the acceptable range. Conclusively, Ar gas plasma-treated GO field emitters can be useful for emission applications in vacuum devices.