Field Emission Devices Research Articles

Electron field emission property of NiO-decorated ZnO nanorods grown on diamond films

ZnO/micron diamond (MCD) composite structure combines two wide-band gap semiconductor materials, providing stable performance suitable for high-performance electron field emission (EFE) devices operating in various complex environments. Nonetheless, the optical and electrochemical limitations of ZnO constrain its effectiveness. Typically, NiO can compensate these inherent defects in ZnO, thereby enhancing the performance of field-emitting devices. In this research, NiO-decorated ZnO thin films were fabricated on diamond surfaces using hydrothermal/sol-gel two-step method. The impact of varying Ni doping concentrations caused by nickel acetate solutions on the field emission properties was thoroughly investigated. Furthermore, this study involved the fabrication of NiO-decorated ZnO/micron diamond heterojunction composite structures, exploring the impact of the structure on the optoelectronic performance of the devices. The Ni doping concentration increases in the NiO films formed between the ZnO nanorods, the doped Ni exists in the ZnO/MCD composite structure as both Ni2+ and Ni3+, which are important materials for semiconductor electronic devices. The NiO decoration process induced the creation of defect levels within the bandgap of the nanorod array structure, consequently enhancing the photoluminescence performance of ZnO. Furthermore, the interaction between NiO and ZnO facilitated the formation of a p-n junction at the interface, generating an internal electric field. This electric field significantly improved the current conduction field and maximum current density of ZnO, thereby enhancing its electric field emission performance. The optical and electrical properties of ZnO nanorods doped at 0.1M exhibited the most favorable characteristics among all tested samples. At a doping concentration of 0.1 M, the turn-on electric field reaches a minimum value of 0.96 V/μm and the maximum current density J reaches a maximum value of 2.54 mA/cm2. These results offer novel insights for advancing the development of integrated broadband optical devices.

Maximizing the notional area in single tip field emitters

One of the critical aspects in advancing high-brightness field emitter devices is determining the conditions under which single-tip emitters should be constructed to optimize their emission area. Recent experiments have explored varying the axis ratio ξ of the cap of a single-tip emitter, ranging from an oblate semi-spheroid to a prolate shape, mounted on a nearly cylindrical conducting body. In this work, we present a strategy, based on high-accuracy computer simulations using the finite element technique, to maximize the emission area of those single-tip emitters. Importantly, our findings indicate that the notional emission area achieves its maximum when the emitter’s cap is adjusted to an oblate semi-spheroid with a characteristic axis ratio ξC≈0.85. We do a comparison of notional emission area as a function of ξ for an ellipsoidal emitter on a post and compare these results from other emitter configurations, which are feasible to fabricate.

Diode-Like Field Emission Devices Fabricated by Standard 0.35-μm CMOS MEMS Process

Diode-Like Field Emission Devices Fabricated by Standard 0.35-μm CMOS MEMS Process

Recent Excellent Optoelectronic Applications Based on Two-Dimensional WS2 Nanomaterials: A Review.

Tungsten disulfide (WS2) is a promising material with excellent electrical, magnetic, optical, and mechanical properties. It is regarded as a key candidate for the development of optoelectronic devices due to its high carrier mobility, high absorption coefficient, large exciton binding energy, polarized light emission, high surface-to-volume ratio, and tunable band gap. These properties contribute to its excellent photoluminescence and high anisotropy. These characteristics render WS2 an advantageous material for applications in light-emitting devices, memristors, and numerous other devices. This article primarily reviews the most recent advancements in the field of optoelectronic devices based on two-dimensional (2D) nano-WS2. A variety of advanced devices have been considered, including light-emitting diodes (LEDs), sensors, field-effect transistors (FETs), photodetectors, field emission devices, and non-volatile memory. This review provides a guide for improving the application of 2D WS2 through improved methods, such as introducing defects and doping processes. Moreover, it is of great significance for the development of transition-metal oxides in optoelectronic applications.

Metal atom doping with GeC: Tuning electronic, magnetic and electrocatalytic hydrogen evolution

The crystal structure stability, electronic and magnetic properties, field emission, and catalytic properties of the metal-doped GeC systems are investigated by the first principles. The Ef (formation energy) in the range of −5.713 to −14.240 eV indicates that the metal-doped GeC systems have energy stability. The Al-, Cr-, Fe-, Co-, Cu-, and Zn-doped GeC systems exhibit metallic properties, but the Ti-, V-, Mn-, and Ni-doped GeC systems retain semiconductor properties. Notably, the V-, Cr-, Mn-, Fe-, Co-, Cu-, and Zn-doped GeC systems exhibit magnetism due to doping effects. In addition, the Ti-, V-, Cr-, Mn-, Fe-, and Co-doped GeC systems have field emission properties relative to the intrinsic GeC due to the decrease of work function. Importantly, the low over-potential indicates that the doping systems have strong electro-catalytic hydrogen production ability. Therefore, the metal-doped GeC has potential applications in spintronic, field emission devices, and electro-catalytic hydrogen production.

Ordered silicon nanocone fabrication by using pseudo-Bosch process and maskless etching

Nanocone arrays are widely employed for applications such as antireflection structures and field emission devices. Silicon nanocones are typically obtained by an etching process, but the profile is hard to attain because anisotropic dry etching generally gives vertical or only slightly tapered sidewall profiles, and isotropic dry plasma etching gives curved sidewalls. In this work, we report the fabrication of cone structures by using masked etching followed by maskless etching techniques. The silicon structure is first etched using fluorine-based plasma under the protection of a hard metal mask, with a tapered or vertical sidewall profile. The mask is then removed, and maskless etching with an optimized nonswitching pseudo-Bosch recipe is applied to achieve the cone structure with a sharp apex. The gas flow ratio of C4F8 and SF6 is significantly increased from 38:22 (which creates a vertical profile) to 56:4, creating a taper angle of approximately 80°. After subsequent maskless etching, the sidewall taper angle is decreased to 74°, and the structure is sharpened to give a pointed apex. The effect of an oxygen cleaning step is also studied. With the introduction of periodic oxygen plasma cleaning steps, both the etch rate and surface smoothness are greatly improved. Lastly, it was found that the aspect ratio-dependent etching effect becomes prominent for dense patterns of cone arrays, with a greatly reduced etch depth at a 600 nm pitch array compared to a 1200 nm pitch array.

Enhanced field emission characteristics of WS2 nano-films by diamond film and Mo film

WS2 is a type of transition metal chalcogenide materials (TMDCs) that exhibits exceptional photoelectric properties. Due to its atomically sharp edges, WS2 has the capability to enhance the electric field around its edges, thus presenting significant potential in field emission applications. In this study, the electron beam vapor deposition (EBVD) system and microwave plasma chemical vapor deposition (MPCVD) system were used to prepare a series of single-layer WS2 films，single-layer diamond films and diamond/WS2 nano-composite films on N-type highly doped Si substrate, and Mo/WS2 nano-composite films were prepared on Al2O3 ceramic substrate. Based on the characterization and analysis of the microstructure and chemical composition of each thin film layer in the above film devices, the field emission (FE) characteristics of each thin film device are compared and studied. The results demonstrate that the maximum FE current density of diamond/WS2 nano-composite film device is 912 μA/cm2, which is 2.7 times of the maximum FE current density of Mo/WS2 nano-composite film device 330 μA/cm2, and 3.4 times of the maximum FE current density of the single-layer diamond thin film device 267 μA/cm2. The single layer WS2 film did not exhibit measurable FE performance. The working principles of thin film field emission devices with various structures are introduced. It is considered that the diamond layer plays the role of electron accelerating layer, which not only effectively improves the FE characteristics of diamond/WS2 nanocomposite film, but also improves the repeatability and long-term stability of diamond/WS2 nanocomposite film FE devices.

Nitrogen admixture effects on growth characteristics and properties of carbon nanowalls

The plasma functionalization of carbon nanowalls (CNWs) is of great interest due to their potential applications in electron field emission and energy storage devices. In this study, the effects of nitrogen on the growth and properties of CNWs are thoroughly investigated by varying a wide range of the N2 concentrations in the CH4/H2/N2 discharge plasma. Nitrogen-doped carbon nanowalls (NCNWs) were synthesized in a single-step growth using the hydrogen radical injection plasma-enhanced chemical vapor deposition technique. The formation of dense NCNWs was found to be enhanced by nitrogen and was three times higher in the sample with a 150 sccm N2 flow rate than in the sample without N2 addition (N-0). As the N2 concentration increased from 0 to 200 sccm, the morphology of CNWs changed from relatively straight to curly-like nanowall structures. A high-resolution optical emission spectroscopic observation shows that as N2 flow increased, CN radicals became the dominant species, suppressing the formation of C2 and CH. Photoelectron spectroscopy analysis revealed the nitrogen doping effect on graphene layers at high N2 concentrations. According to Raman and Transmission Electron Microscopy analyses, the NCNWs had more branched and thicker nanowalls with higher defect concentrations than the N-0 sample. The wettability of NCNWs was improved, particularly for the sample with a N2 flow rate of 150 sccm.

Study on field emission performance of SrTiO3 film enhanced by LiF film

A series of monolayer SrTiO3 films and LiF/SrTiO3 bilayer films were prepared on n-Si substrates by using vacuum electron beam vapor deposition (EBVD) technology. The morphologies and thicknesses of the SrTiO3 film and LiF film were controlled through adjustments and optimization of the growth conditions as well as deposition time. The experimental results show that the field emission performance of SrTiO3 film is significantly improved after LiF film is added. Under the research conditions in our laboratory, a large number of LiF/SrTiO3 bilayer film field emission devices have been tested and analyzed in the wide range of LiF film thickness (10–300 nm), and the effective field emission LiF film thickness (50–90 nm) was initially determined. Further study shows that the LiF/SrTiO3 bilayer film has the best field emission performance when the optimal LiF film thickness is 70 nm, and its maximum field emission current density can reach 305.48 μA/cm2. The field emission current density of the LiF/SrTiO3 bilayer thin film device is nearly 4 times compared to that of the monolayer SrTiO3 film when the applied electric field intensity reaches 9.05 V/μm. All the field emission devices exhibit excellent functioning stability and experimental reproducibility.

Surface modification of a biomass-derived self-supported carbon nano network as an emerging platform for advanced field emitter devices and supercapacitor applications.

Herein, a self-supported carbon network is designed through the sole pyrolysis of Carica papaya seeds (biomass) without any activation agent, demonstrating their field emission and supercapacitor applications. The pyrolysis of seeds in an argon atmosphere leads to the formation of interconnected, rod-like structures. Furthermore, the hydrofluoric acid treatment not only removed impurities, but also resulted in the formation of CaF2 nanocrystals with the addition of F-doping. From the field emission studies, the turn-on field values defined at an emission current density of ∼10 μA cm-2 were found to be ∼2.16 and 1.21 V μm-1 for the as-prepared carbon and F-doped carbon, respectively. Notably, F-doped carbon exhibits a high emission current density of ∼9.49 mA cm-2 and has been drawn at an applied electric field of ∼2.29 V μm-1. Supercapacitor studies were carried out to demonstrate the multi-functionality of the prepared materials. The F-doped carbon electrode material exhibits the highest specific capacitance of 234 F g-1 at 0.5 A g-1. To demonstrate the actual supercapacitor application, the HFC//HFC symmetric coin cell supercapacitor device was assembled. The overall multifunctional applicability of the fabricated hybrid structures provides a futuristic approach to field emission and energy storage applications.

Effect of ultraviolet light on field emission performance and lifetime of lateral field emitter devices

Lateral field emission devices have been characterized before and after ultraviolet (UV) light exposure. Two types of planar device structures, diode and bowtie, were studied. These nanoscale devices have 9–15 nm tip-to-tip (bowtie) or tip-to-collector (diode) dimensions with the tips fabricated from Au/Ti. Typical currents of 2–5 nA per tip at 6 V were measured. It was observed that after UV exposure, the collected current was reduced by >28% for the case of a bowtie device; whereas the current was reduced by >39% for the case of a diode device. This reduction can be attributed to water vapor desorption on the dielectric surface between the structures, which in turn reduces surface leakage. The Fowler–Nordheim plot showed a straighter line after UV exposure. After the I-V test, the UV-exposed devices were placed on lifetime tests in a vacuum of <10−8 Torr and were biased at 5 V DC. After 2600 h, an abrupt current decrease was observed: ∼25% for the case of the bowtie and ∼28% for the case of the diode device. Scanning electron microscope images of the bowtie and diode devices showed damage to the tips.

Adsorption of metals on Si9C15 monolayer for optoelectronic applications

Two dimensional materials have a bright application prospect in the field of optoelectronic devices. As a newly discovered polymorph of the third-generation semiconductor SiC, Si9C15's single-layer structure may have excellent optoelectronic properties, which has significant practical implications for the study of two-dimensional Si9C15. By employing the first-principles density functional theory, a comprehensive analysis is performed on the electronic, magnetic, work function, and optical absorption properties of a monolayer structure Si9C15 with metal atom adsorption. The adsorption of different metal semiconductors has changed their properties. The adsorption of metal atoms not only reduces the work function of Si9C15, but also enhances its light absorption ability in the visible light region. This finding highlights the potential for enhancing the optical properties of the Si9C15 system through metal adsorption. The utilization of spherical metal nanoparticles on Si9C15 nanosheets to induce local surface plasmon resonance is an exciting development. The results indicate that the Si9C15 system adsorbed with metal atoms could be employed in the manufacturing of spin electronic device, field emission devices, and solar photovoltaic devices. This suggests that the improved optical properties of the Si9C15 system could have significant implications for advancing these technologies.

Maximizing the performance of a field emission device by profiling the emitter’s height distribution

Electrostatic depolarization in clusters of emitters regularly spaced and with uniform height causes the emission to concentrate on the outer corners, suppressing the relative emission contribution from center emitters. In this Letter, we performed extensive three-dimensional computer simulations to show that profiling the height distribution of the emitters significantly compensates for the electrostatic depolarization and homogenizes the emitted current per emitter. Importantly, a minimum standard deviation on the currents from individual emitters shows the route to find the ellipsoidal height profile to achieve optimized conditions. This implies a maximized macroscopic current extractable from the device since every emitter contributes approximately the same before burning out. Our findings are expected to guide developments on new field electron emission devices.

Estimation of Size and Lattice Strain of ZnO/Ag Nanowires Based on Williamson-Hall Analysis

Zinc oxide (ZnO) is known as an important semiconductor which has been studied extensively in the past few years due to its fundamental and technological importance, Itsmany attractive properties, such as wide bandgap (3.37 eV), large exciton binding energy and excellent chemical stability, suggest a great many possible practical applications such as in gas sensors, ceramics, field-emission devices and luminescent materials and therapeutic , size and crystal morphology play important roles in these applications, which have driven researchers to focus on the synthesis of nanocrystalline ZnO. This work is aimed to the development and characterization of zinc oxyde nanowires for therapeutic applications. ZnO nanowires are elaborated by hydrothermal method using a novel synthesized protocol. The elaboration hydrothermal conditions were optimized in order to have the longest nanowires with the lowest diameter. The structural, morphological and elementary analysis of the growth NWs was carried out by X-ray Diffraction (DRX), Scanning Electron Microscopy (SEM) and Energy Dispersive spectroscopy (EDS). The XRD results revealed that the sample product was crystalline with a hexagonal wurtzite phase. transmission electron microscopy (TEM) showed single-crystal ZnO NPs with nearly wires shapes. The crystalline development in the ZnO-Nws was investigated by X-ray peak broadening. The Williamsone Hall (W_H) analysis and sizee strain plot method were used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of the ZnO-Nws.

An enhanced field emission for display devices arises from the assembling of ZnO@MOF/MWCNTs

In this study, we propose a new, simple technique for raising the efficiency of field emission devices based on metal organic framework composites. Multi-walled carbon nanotubes (MWCNTs) and ZnO are used in the fabrication of metal-organicframeworks (MOFs) in this technique. This is explained by the composites unique structural structure, which offers a lot of easily available electro active sites, low surface work function, and improved electronic conductivity. One of the less complicated and more economical synthesis methods is used to synthesize the ZnO@MOF/MWCNTs composite. The material's precise morphological and structural features have all been investigated using Raman, FE-SEM, EDX, FTIR, and UV–Visible investigations. The ZnO@MOF/MWCNTs field emitter show impressive and stable field emission properties, such as a low turn-on electric field 0.50 V/μm and a high emission current density 219.15 mA/cm2.Our research revealed an easier way for boosting the electron field emission utilized in different field emission display systems that are based on MOFcomposites.

Three-Dimensional Monte Carlo Simulation of Silicon Field Emitters

Using a particle-based Monte Carlo modeling approach we study the characteristics of silicon field emitter devices. We use an unstructured mesh based on tetrahedral elements to describe the device geometry in 3-D, and we treat silicon and vacuum on equal footing when tracking electrons in both regions. We compare several tunnel models by evaluating the current-voltage characteristics of a single field-emitting silicon pillar. Furthermore, we perform an initial model validation, comparing the simulated current–voltage characteristic to the measured values for gated silicon filed emitter.

Lateral nanoscale field emission comb for frequency mixing

Nanoscale field emission devices are promising candidates to design high-frequency electronics due to the lack of scattering in the vacuum channel that enables ballistic transport. In-plane devices are relatively easy to fabricate with current fabrication techniques and offer sub-fF capacitance. In this work, the characteristics of lateral gold multi-tip field emission arrays are studied. Vacuum gaps between the electrodes of 30 nm are fabricated, which allow < 10 V operation. The effect of number of emitting tips on measured current is investigated. By taking advantage of the strong non-linearity in the emission characteristic, frequency mixing in the MHz range is also demonstrated.

Tubular Diamond as an Efficient Electron Field Emitter

Herein, we present a straightforward and cost-effective procedure for producing conductive diamond tubes on the surface of porous carbon nanotube hollow fibers using successive 10-pulsed laser annealing shots and 6 h of hot filament chemical vapor deposition techniques. Room-temperature Raman and X-ray diffraction spectra reveal the signature T2g peaks near 1332.4 cm–1 and 111 planes of diamonds near 43.9°, respectively. A low turn-on field (ETO) ∼1.85 V/μm@1 μA/cm2 and a threshold field (ETH) ∼2.54 V/μm@10 μA/cm2 were observed for the tubular diamond structures. The field enhancement factor (β) was calculated at 3594 and highly stable field emission current stability was observed over a long period of 4 h. For the first time, a good insight into the field emission results of the diamond is established with the structural, electronic properties, and the work function (φ) ∼4.84 eV analysis conducted by the density functional theory simulation. Finite electronic states at the Fermi level are observed beyond a band gap, and it demonstrates the wide-band gap (4.4 eV) semiconducting nature of the diamond. The Bader charge analysis and maximum entropy method pattern revealed the negative electron affinity of the diamond, and it is responsible for the emission of electrons from the conduction band of the diamond. Besides, the accumulation of charge carriers, which contributes to the electric field emission, takes place due to the weak π bonds of carbon atoms. The low turn-on field, the high field enhancement factor, and the good field emission current stability of tubular diamond offer great prospects for future efficient and low-cost field emission devices.

Study of photoluminescence behaviors and Judd-Ofelt analysis of Eu3+ doped double perovskite Ba2GdSbO6 phosphor for highly pure and strong red-light generation

An array of Eu3+ doped Ba2GdSbO6 luminescent materials have been synthesized by the conventional solid-state (high temperature) reaction route. Surface morphology has been studied via Field Emission Scanning Electron Microscopy. The structural and optical behaviors have been studied using X-Ray Diffraction (XRD), FTIR, Raman spectroscopy, Diffuse reflectance spectroscopy, Photoluminescence excitation (PLE), and Photoluminescence emission (PL) spectra. FTIR and Raman's spectra provided the chemical functional group and different vibrational levels within the samples. The calculated optical band gap was 4.40 eV and 4.47eV for pure and optimized samples respectively. Photoluminescence emission curves have been recorded for 245 nm of excitation wavelength and the highest emission peak was focused at 595 nm corresponding to 5D0 → 7F1. Similarly, the Photoluminescence excitation curves were monitored at the emission wavelength of 595 nm and a broad charge transfer band (CTB) was observed from 230 to 285 nm. The emission spectra show the concentration quenching effect beyond the 2 mol% Eu3+ concentration. The corresponding transitions of Eu3+ were further utilized to obtain the Judd-Ofelt (J-O) transition intensity parameters Ωλ (λ = 2, 4) for each sample. Additionally, by studying decay kinetics, the average lifetime of the red emission of the samples has been evaluated, which was 4.622 ms. The photometric study also reveals the CIE coordinates, color purity and CCT values of the proposed phosphor material. Thus, the results obtained from these characterizations, suggest that the prepared sample may behave as a potential candidate in the case of UV-excited red light-emitting phosphor material for light-emitting diodes and field emission devices.

Effect of praseodymium coating on electron emission from a nanoscale gold field emitter array

Although field emission devices are inherently robust to high temperature and radiation environments as well as have high switching speeds, their development has been hindered by high voltages that are typically required for their operation. In this work, we investigate the effect of thin-film praseodymium (Pr) coating on the emission characteristics of a lateral gold (Au) field emitter array. Because Pr has a significantly lower work function than Au, it is expected to increase the field emission measured current. Pr is deposited onto the device via thermal angled evaporation in a custom-built vacuum chamber with in situ electrical characterization capability. Our experiments demonstrate that a 10 nm-thick Pr layer reduces the turn-on voltage by almost half compared to the noncoated Au structure. These results are promising for the development of power-efficient, low voltage field emission electronics.