Promising Field Emission Research Articles

Nanostructured tungsten trioxide developed from environmentally friendly green process as a promising cathode for excellent field emission

Extensively explored as cathodes for field emission, nanostructured metal oxides play a crucial role in diverse applications such as microwave amplifiers, renewable energy systems, flat panel displays, and micro-electronics. The quest for high current density, low threshold field, and stable field emission persists. In present study, we introduce a green synthesis approach using vegetable oil as a reaction medium to produce hexagonal tungsten trioxide (h-WO3). The structural analysis confirmed the formation of h-WO3 with a nanorod-like morphology. The spin-coated h-WO3 film on a silicon substrate exhibited promising field emission properties, including a field enhancement factor (β) of 1596 and a turn-on field of 4.60 V/μm, comparable to reported values. This research opens avenues for the cost-effective and scalable utilization of h-WO3 as an electron emitter in advanced optical and electrical devices.

Synthesis, characterization and field emission studies of NiO-rGO nanocomposite

In this work, NiO-rGO nanocomposite was synthesized by hydrothermal/solvothermal method on nickel foil. The as-synthesized product was subjected to various characterizations such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Raman spectroscopy, in order to reveal its phase, morphology and structure. The SEM analysis reveals formation of nearly vertically oriented and randomly distributed nanoflakes of NiO-rGO nanocomposite on entire substrate surface. The Raman spectrum of the NiO-rGO composite showed characteristic D and G bands of rGO, confirming its presence in the composite. The NiO-rGO composite emitter showed promising field emission behaviour. The values of turn-on and threshold fields, defined at emission current density of 1 and 10 µA/cm2, were observed to be 1.8 and 2.25 V/µm, respectively, which are comparable to alike composite emitters. Furthermore, from the NiO-rGO composite emitter, maximum current density of 719 µA/cm2 has been extracted at an applied field of 4.5 V/µm. The observed results imply potential of NiO-rGO composite emitter for application in vacuum microelectronic devices.

Hot-filament CVD Growth of Vertically-aligned Carbon Nanotubes on Support Materials for Field Electron Emitters

Carbon nanotubes are used in applications such as energy storages, electronic devices. For these applications, direct assembly of the well aligned and densely packed CNTs (VACNTs) on electrically conducting substrates is of interest. In this paper, we report a direct growth of the VACNTs on several substrates by using hot-filament chemical vapor deposition (hot-filament CVD) and a catalytic buffer-layer structure. The buffer layer was the Aluminum (Al) thin film used together with iron (Fe) as the catalyst. It was found that the underneath layer (Al) was critical for obtaining the VACNT forests with high purity and good contact. The as-fabricated VACNT/support-material structures are object to test field electron emission properties. Testing results of the VACNT samples demonstrated promising field emission characteristics in term of high emitting currents.

VSe2-reduced graphene oxide as efficient cathode material for field emission

Field emission properties of pristine VSe2 and its hybrid with reduced graphene oxide (RGO) have been investigated in detail. Promising field emission performance were noted with lower values of turn-on and threshold fields of ∼1.3 V μm−1 and 2.12 V μm−1 respectively for the VSe2/RGO hybrid which is much more superior than that of pristine VSe2 emitter and other 2D materials. Density Functional Theory (DFT) simulations have also been performed to qualitatively support our experimental observations through demonstration of Density of States and computation of work function for pristine VSe2 and hybrid VSe2/RGO. The lowering of work function and appearance of additional states near Fermi level from carbon p orbital of RGO is responsible for superior field emission characteristics in hybrid VSe2/RGO compared to pristine VSe2 which supports our experimental observations. Our experimental data and theoretical insight from electronic structure simulations strongly infer that the synthesized hybrid VSe2/RGO has the potential to be tailored as efficient and high performance cathode material in field emission based devices.

High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2–30 walls with an inner diameter of 3–8 nm. Raman spectrum analysis shows G-band at 1580 cm−1 and D-band at 1340 cm−1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

Correction: Synthesis of Te-doped ZnO nanowires with promising field emission behavior

Correction for ‘Synthesis of Te-doped ZnO nanowires with promising field emission behavior’ by Farid Jamali-Sheini, RSC Adv., 2016, 6, 115335–115344.

Synthesis of Te-doped ZnO nanowires with promising field emission behavior

In the current study, a successful synthesis of ZnO nanowire films doped with Te was performed through electrodeposition on the zinc foil followed by annealing in air for 4 hours at 400 °C.

Laser exfoliation of 2D black phosphorus nanosheets and their application as a field emitter

Highly crystalline two dimensional (2D) few layered black phosphorus (BP) nanosheets have been synthesized via a one step facile laser irradiation technique under optimized experimental conditions. The BP material shows promising field emission performance.

Improved field emission properties of CuO nanowire arrays by coating of graphene oxide layers

Graphene oxide (GO)-coated copper oxide (CuO) nanowire arrays were prepared as field emission cathodes using a solution process, in which CuO nanowires were grown on Cu substrates by a low-temperature hydrothermal process and the covering of GO sheets was carried out using an electrostatic self-assembly method. The field emission investigations of GO/CuO cathode showed a low turn-on field of 3.7 V/μm and a high enhancement factor (2080) compared to those of bare CuO nanowires. Furthermore, the emission current was stable without any attenuation during the testing. The GO/CuO composite nanostructures are promising field emission cathodes in field emission application.

Synthesis of single-crystalline sodium vanadate nanowires based on chemical solution deposition method

We have demonstrated a simple and convenient chemical solution deposition method without employing catalysts, surfactants or carrier gases to synthesize sodium vanadate (β-Na0.33V2O5) nanowires (NWs) supported on conducting substrates. Both high resolution transmission electron microscopy and X-ray diffraction studies indicate the single-crystalline properties of such NWs. The morphologies of the β-Na0.33V2O5 NWs can be controlled by varying the growth temperature and duration. Moreover, the β-Na0.33V2O5 NWs show promising field emission (FE) performance with a high current density (54 mA cm−2), low turn-on field voltage (0.60 V μm−1) and a high degree of emission stability. These results suggest that β-Na0.33V2O5 NWs can serve as a candidate material for future electronic and FE devices.

Facile synthesis of Ag nanowire–rGO composites and their promising field emission performance

Crystalline, ultra long silver nanowires, few-layered rGO and their rGO–Ag NW nanocomposite have been synthesized using a polyol reflux technique under optimized experimental conditions.

Vapour–liquid–solid growth of one-dimensional In2Se3 nanostructures and their promising field emission behaviour

Single crystalline ultra long In2Se3 nanowires have been grown via thermal evaporation route on Au/Si substrates and explored its field emission investigations at ∼1 × 10−8 mbar.

Efficient Field Emission from Vertically Aligned Cu2O1‐δ(111) Nanostructure Influenced by Oxygen Vacancy

In the architecture described, cuprous oxide (Cu2O) is tamed to be highly (111) plane oriented nanostructure through adjusting the deposition postulate by glancing angle deposition technique. In the controlled atmosphere oxygen vacancy is introduced into the Cu2O crystal subsequently fostering an impurity energy state (Eim) close to the conduction band. Our model of Cu2O electronic structure using density functional theory suggests that oxygen vacancies enhance the electron donating ability because of unshared d‐electrons of Cu atoms (nearest to the vacancy site), allowing to pin the work function energy level around 0.28 eV compared to the bulk. This result is also complemented by Kelvin probe force microscopy analysis and X‐ray photoelectron spectroscopy method. Oxygen vacancy in Cu2O (Cu2O1‐δ) exhibits promising field emission properties with interesting field electron tunneling behavior at different applied fields. The films show very low turn‐on and threshold voltages of value 0.8 and 2.4 V μm−1 respectively which is influenced by the oxygen vacancy. Here, a correlation between the work function modulation due to the oxygen vacancy and enhancement of field emission of Cu2O1–δ nanostructure is demonstrated. This work reveals a promising new vision for Cu2O as a low power field emitter device.

Multifunctional polyaniline–tin oxide (PANI–SnO2) nanocomposite: Synthesis, electrochemical, and field emission investigations

ABSTRACTSynthesis of PANI–SnO2 nanocomposite has been performed using a simple two step chemical oxidative polymerization route. The structural, morphological and chemical properties of the as‐synthesized PANI–SnO2 nanocomposite have been revealed by various characterization techniques such as SEM, TEM, XRD, FTIR, and XPS. Interestingly the as‐synthesized PANI–SnO2 nanocomposite exhibits supercapacitance value of 721 F g−1 with energy density 64 Wh kg−1, which is noticed to be higher than that of pristine SnO2 and PANI nanostructures. Furthermore, the galvanostatic charge–discharge characteristics revealed pseudocapacitive nature of the PANI–SnO2 nanocomposite. The estimated values of charge transfer resistance and series resistance estimated from the Nyquist plot are found to be lower. Along with the supercapacitive nature, PANI–SnO2 nanocomposite showed promising field emission behavior. The threshold field, required to draw emission current density of 1 μA/cm2, is observed to be 0.90 V/μm and emission current density of 1.2 mA/cm2 has been drawn at applied field of ∼2.6 V/μm. The emission current stability investigated at preset values of 0.02 and 0.1 mA/cm2 is observed to be fairly stable over duration of more than 3 h. The enhanced supercapacitance values, as well as, the promising field emission characteristics are attributed to the synergic effect of SnO2 nanoparticles and PANI nanotubes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41401.

Vapor–Liquid–Solid Growth of One-Dimensional Tin Sulfide (SnS) Nanostructures with Promising Field Emission Behavior

Single-crystalline ultralong tin sulfide (SnS) nanowires has been grown by a thermal evaporation technique under optimized conditions on gold-coated silicon substrates, and for the first time, field emission investigations on the SnS nanowires at the base pressure of 1 × 10(-8) mbar are reported. It has been revealed that the surface morphology of the as-synthesized SnS nanostructures is significantly influenced by the deposition temperature and duration. Structural and morphological analyses of as-synthesized SnS nanostructures have been carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). To understand the optical and electronic properties of as-synthesized SnS nanowires, ultraviolet-visible (UV-vis), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) studies were carried out. The SEM and TEM measurements reveal the formation of ultralong SnS nanowires, with an average diameter of 80 nm. A plausible explanation on the vapor-solid-liquid (VLS) growth mechanism based on the experimental results and reported literature has been presented. Furthermore, the field emission characteristics of the SnS nanowires are found to be superior to the other metal chalcogenide nanostructures. The synthesized SnS nanowire emitter delivers a high current density of ∼2.5 mA/cm(2) at an applied electric field of ∼4.55 V/μm. The emission current stability over a period of 6 h is observed to be good. The observed results demonstrate the potential of the SnS nanowire emitter as an electron source for practical applications in vacuum nano/microelectronic devices.

Work Function Measurement for Ag-TCNQ (TCNQ = Tetracyanoquinodimethane) Nanowires

The Ag-TCNQ (TCNQ = tetracyanoquinodimethane) nanowires synthesized by a vapor transport reaction exhibit promising field emission properties. Their effective work function at high applied electric field was estimated to be about 1.70 eV according to the Fowler-Nordheim (F-N) theory. In this work, we directly measured the intrinsic work function of Ag-TCNQ nanowires via the ultraviolet photoemission spectroscopy (UPS). According to the threshold binding energy, the work function is obtained to be 5.45 eV, which shows a large discrepancy with the preivous estimation based on F-N theory. The reductive effecitive work function during the field emission is mainly attributed to the morphology-induced enhancement of the nanowire array.

Promising electron field emitters composed of conducting perovskite LaNiO3 shells on ZnO nanorod arrays

We report a semiconductor–perovskite composite system with promising field emission properties. The composite system was fabricated by sputtering perovskite LaNiO3 (LNO) shells on one dimensional (1D) well-aligned hydrothermally produced ZnO nanorod arrays (ZNAs). The ZNA–LNO core–shell hetero-structures were demonstrated to be much more efficient field emitters than ZNAs. Since the work function of LNO (4.5 eV) is lower than that of ZnO (5.3 eV), a shallow well is formed in thermal equilibrium in the ZNA–LNO heterojunction. When an electric field is applied, the produced well is of much benefit for the flow of electrons from the GZO seed layers through the ZNA to the LNO shells. Consequently, the emission of electrons into vacuum by tunneling is easily realized due to the low work function of the LNO coatings. Our 1D semiconductor–perovskite composite system provides a prospect for the development of practical field emission electron sources.

Role of alkali metal adsorption and defect position on the work function of a (5, 5) capped single-walled carbon nanotube

The authors used first-principles calculations to investigate the influence of alkali metal (Li/Na/Cs) adsorption and defect position on the work function of a (5, 5) armchair single-walled carbon nanotube (CNT) with a capped edge. The atomic Cs adsorption can more effectively reduce the work function of the CNT than the atomic Li/Na adsorption. Adsorption positions have a measurable impact on the work function of the CNT. Any vacancy defect on the tip can raise the work function of the CNT regardless of whether or not an alkali metal atom is absorbed. The variations of work functions are mainly attributed to the change of Fermi levels induced by charge redistributions. The alkali metal adsorption can also transform the semiconducting CNT into a metallic tube, which is significant for the CNTs as a promising field emission cold cathode material.

Synthesis and field emission properties of nickel oxide nanoplatelets prepared by simple novel technique

Single crystalline NiO nanoplatelets were successfully synthesized by new facile method at 200 °C. The morphology and microstructure were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD measurement indicated that the prepared sample had typical cubic structures. The SEM investigation confirmed that the product was of the form of nanoplatelets. These nanoplatelets have average width length 250 nm and thickness of 20 nm. The field emission measurements demonstrate that the NiO nanoplatelets show a promising field emission property. The improved field emission is attributed to the local field enhancement factor at the nanoplatelets. The results confirm the importance of the morphology of nanomaterial in field emission.

Promising Field Emission Characteristics of Polyaniline Nanotubes

Polyaniline (PANI) nanotubes have been synthesized employing chemical polymerization with acetic acid as dopant. The synthesized PANI nanotubes were characterized by Scanning electron microscope (SEM), Transmission electron microscope (TEM), Uv-visible spectroscopy and Fourier transform infrared spectroscopy (FTIR). The SEM and TEM analysis clearly reveals the formation of PANI nanotubes, with outer diameter in the range of 50–150 nm and length in several microns. The Uv-visible and FTIR spectra exhibit characteristic features corresponding to electrically conducting phase of doped PANI. Field emission (FE) studies of the PANI nanotubes were performed in planar diode configuration at a base pressure of ∼1 × 10−8 Torr. From the FE results, value of the turn on field required to draw an emission current density of 1 μA/cm2 was found to be 1.55 V/μm and current density of 1 mA/cm2 has been drawn at an applied field of 3.8 V/μm. The PANI nanotubes emitter exhibited good emission current stability at pre-set value of 1 μA over duration of more than 3 h. The ease of synthesis route and interesting field emission properties recommend the PANI nanotubes as a promising material for field emission based applications in vacuum micro-nanoelectronic devices.