Field Emission Triode Research Articles

Nanogaps Mediated Field Effect-Controlled Field Emission Triode

Nanogaps Mediated Field Effect-Controlled Field Emission Triode

Nanoscale Vacuum Field Emission Triode With a Double Gate Structure

A planar lateral Vacuum Field Emission Triode (VFET) with a double gate structure is proposed to improve the gate modulation characteristics in this letter. The preparation of this double gate structure is obtained by using the mature bottom gate VFET manufacturing process without any additional dedicated masks. The emission characteristics of the fabricated VFET under vacuum and atmosphere condition are measured. The experimental results demonstrate that both the bottom gate and the top gate can effectively control the emission electrons in the vacuum channel with width of about 110–200 nm which is successfully prepared by the electro-forming process. The operating mechanism of the device is basically the same as that of the plane-bottom gate VFET, and the device has achieved good field electron emission characteristics and double-gate modulation characteristics. Meanwhile, the vacuum channel is covered by the top gate insulator layer, which relaxing the vacuum requirement and improving the collection efficiency of emitted electrons by drain electrode about 50% in air.

Analysis of the electron emission characteristics and working mechanism of a planar bottom gate vacuum field emission triode with a nanoscale channel.

A planar lateral vacuum field emission triode (VFET) with a nanoscale channel of 80-90 nm was fabricated on a silicon wafer. The nanoscale channel of this vacuum triode was generated by via the electro-forming process (EFP). With the use of a wedge-waist-type conductive film, the distribution of Joule heat during EFP could be guided, which helped to realize the controllable preparation of a nanoscale fissure that served as the vacuum channel. Experimental results revealed that the fabricated device demonstrated good emission characteristics in vacuum and could be operated normally under atmospheric conditions. The triode emission characteristics under atmospheric pressure were preliminarily realized. The field-assisted thermal electron emission for low operating voltage and the Fowler-Nordheim tunneling emission mechanism for voltages greater than the turn-on voltage were used to explain the emission mechanism of the proposed VFET.

Optimization of an Anode Membrane with a Transmission-Type Target in a System of Soft X-Ray Sources for X-Ray Nanolithography

In this paper, we propose a method for optimizing the design and composition of the anode membrane with a transmission-type target as part of a system of soft X-ray sources based on field-emission triodes for performing tasks in the field of X-ray nanolithography. It allows to prevent the degradation of the operating characteristics of the system when significant electrostatic deformation of the anode occurs under the influence of a control electric field in the inter-electrode space of the triodes. For this purpose, the inclusion of an additional control electrode in the system design is considered, which makes it possible to compensate for the deformation of the anode membrane to an acceptable level and thereby stabilize the operation of X-ray sources. A numerical model of the electrostatic deflection of the anode assembly in a modified design is developed, based on which the optimal composition and geometric parameters of the anode membrane with a compensating electrode are determined. In particular, the optimal distance between the anode membrane in the initial (undeformed) state and the compensating electrode was found (equal to 5 μm), at which a minimum voltage difference (about 1.15 kV) should be applied to these electrodes to prevent critical deflection of the membrane (0.72 μm with a membrane radius of 750 µm). It is also shown that, due to their extremely high hardness (>80 GPa), diamond-like films are the most promising material for the anode electrode. The results obtained can also be useful for the development of miniature X-ray generation devices for various applications.

On-Chip Fully Integrated Field Emission Arrays for High-Voltage MEMS Applications

Vacuum-sealed fully integrated diode and triode field emission arrays based on Ti Spindt-type field emitters have been developed in a scalable, CMOS-compatible process directly on Si. Diode characterization in air demonstrates effective vacuum sealing and field emission conduction, with current drivability that scales with array size. Triode characterization in vacuum demonstrates gate-modulated field emission of the output current and highlights new effects observed in a fully integrated geometry with closely spaced electrodes. Demonstrating up to 200-V blocking voltage and similar magnitude punchthrough voltages, the arrays can be utilized as high-voltage devices in CMOS applications or with microelectromechanical systems (MEMS) technologies using post-CMOS MEMS integration techniques. Low-temperature measurements reveal areas of improvement for electrode isolation; combined with the use of improved cathode materials, these devices have the potential to be used in high-power applications.

Оптимизация анодной мембраны с прострельной мишенью в системе источников мягкого рентгеновского излучения для проведения процессов рентгеновской нанолитографии

In this paper, we propose a method for optimizing the design and composition of the anode membrane with a transmission-type target as part of a system of soft X-ray sources based on field-emission triodes for performing tasks in the field of X-ray nanolithography. It allows to prevent the degradation of the operating characteristics of the system when significant electrostatic deformation of the anode occurs under the influence of a control electric field in the inter-electrode space of the triodes. For this purpose, the inclusion of an additional control electrode in the system design is considered, which makes it possible to compensate for the deformation of the anode membrane to an acceptable level and thereby stabilize the operation of X-ray sources. A numerical model of the electrostatic deflection of the anode assembly in a modified design is developed, based on which the optimal composition and geometric parameters of the anode membrane with a compensating electrode are determined. In particular, the optimal distance between the anode membrane in the initial (undeformed) state and the compensating electrode was found (equal to 5 μm), at which a minimum voltage difference (about 1.15 kV) should be applied to these electrodes to prevent critical deflection of the membrane (0.72 μm with a membrane radius of 750 µm). It is also shown that, due to their extremely high hardness (>80 GPa), diamond-like films are the most promising material for the anode electrode. The results obtained can also be useful for the development of miniature X-ray generation devices for various applications.

Field-Emission Staggered Structure Based on Diamond–Graphite Clusters

We have proposed and designed a vacuum field-emission triode structure with high-resistivity semiconducting or insulating micrometer-size right parallelepipeds deposited in the staggered order on the conducting substrate (cathode), as well as a structure with a nanofilm on the cathode, which is formed by evaporated diamond–graphite clusters. It has been shown theoretically and experimentally that the emissivity of these structures is much higher than that of an uncoated cathode.

Very large suspended graphene as an efficient electron-transparent gate electrode

Although a focused electron beam is required in field emission-based various applications, the electron beam is generally diverged in a conventional triode because the gate has a circular aperture through which the electrons are accelerated to reach the anode. To prevent the beam divergence, a suspended multi-layer graphene (MLG) was fabricated on a very large gate aperture to be used as an electron-transparent gate in a field emission triode. The suspended MLG was observed to have several micro-openings with an average diameter of ∼5 μm formed during a transfer. It was observed that the MLG with micro-openings was likely to act as an efficient transparent gate for electrons even with large number of graphene layers, exhibiting a high transmittance of ∼90%. The solid angles of the beams obtained using conventional gate aperture and suspended MLG gate were 0.225 and 0.074 sr, respectively, indicating that the suspended MLG resulted in a focused electron beam. Simulations confirm that the suspended MLG with micro-openings suppresses the beam divergence in a given triode configuration because the MLG results in the flattened electric field profiles between gate and cathode whereas a distorted potential distribution causing beam divergence occurs around the aperture in a conventional triode.

Calculation of a triode field-emission system with a modulator

The electrostatic potential of a triode field-emission system with a modulator that represents a circular diaphragm is calculated. A tip field-emission cathode serves as an emitter. The inner part of the system under study is filled with two insulators. In the calculation of the potential distribution, a real field-emission cathode is changed by a virtual cathode whose surface coincides with an equipotential surface, so that the effect of the cathode on the distribution of the electrostatic potential is simulated as the effect of a finite charged wire that is located at the axis of the system. The separation of variables is used to solve the problem. The potential is represented as an expansion in terms of eigenfunctions, and the expansion coefficients are found from the solution to a system of linear algebraic equations.

Fabrication and Characterization of a Planar Triode Structure Based on Honeycomb Carbon Nanotubes

We report a planar triode with metal-gate-free electrode based on carbon nanotubes. Excellent field emission properties with 1.4 mA/cm2 at the gate voltage of 32 V are obtained. A turn-off phenomenon is observed when the gate voltage decreases to 0 V. The field emission at 1.2 mA/cm2 is recorded for 20 h with the fluctuation of the emission current . The results would be of significance to the development of field emission triode structure in the future.

增强碳纳米管场发射性能的沟槽形冷阴极制作

Based on sintering process and screen printing technique,a novel groove shape cold cathode was developed.The black insulation slurry was sintered to fabricate the bottom insulation layer,in which a gradient surface existed.The silver slurry was screen-printed on the bar electrode. With the baking and sintering process in proper sequence,the silver electrode was formed.Using fine sandpaper,aproper polishing process for silver electrode was conducted,so a smooth electrode surface was obtained.Due to the special silver electrode shape,a larger field enhancement factor was achieved easily.Carbon nanotubes were prepared on the silver electrode to form the field emitters. The dense carbon nanotube layer would cover the silver electrode surface completely.Owing to the special edge field enhancing effect,lots of electrons would be emitted from the carbon nanotube.The top insulation layer was used to restrain the side electron emission of carbon nanotube.With the groove shape cold cathode,a triode field emission display was fabricated,which exhibited good field emission properties and better luminescence image uniformity.Comparing with the common cold cathode field emission display,the turn-on electric field could be reduced from 1.86 V/μm to1.78V/μm,the maximum field emission current had been increased from 1 537μA to 2 863μA,and the maximum luminescence image brightness would be enhanced from 1 386cd/m2 to 1 865cd/m2.The developed fabrication technology had a potential practical application in field emission display.

Fabrication research on the sandwich layered cathode electrode for a triode field emission display prototype

Based on an effective screen-printing process, a novel sandwich layered cathode electrode was developed on a cathode faceplate. The ZnO electrode was sandwiched between an indium tin oxide (ITO) electrode layer and a silver electrode layer, and the carbon nanotube was prepared directly on the exposed ITO electrode layer surface. The cathode potential could be conducted to the carbon nanotube with the sandwich layered cathode electrode. Using the carbon nanotube as a field emitter, a triode field emission display prototype with a sandwich layered cathode electrode was fabricated, which possessed a better field emission characteristic, higher luminous brightness and better emission image luminance uniformity. The turn-on electric field was 1.88 V/μm and the measured maximum field emission current was 2273.6 μA at 3.19 V/μm. By the method of adjusting the field emission current, the electron-emitting uniform capacity of the carbon nanotube cold cathode could be modified, and the emission image luminance uniformity and the emission current stability of triode field emission display prototype was also be improved significantly. The emission current fluctuation of the sandwich layered cathode electrode type field emission display was less than 1.1%. Furthermore, the total manufacture cost of the triode field emission display prototype was low.

Nanodiamond vacuum field emission device with gate modulated triode characteristics

A three-electrode nanodiamond vacuum field emission (VFE) device with gate modulated triode characteristics is developed by integrating nanodiamond emitter with self-aligned silicon gate and anode, employing a mold transfer technique in conjunction with chemical vapor deposition of nanodiamond. Triode behavior showing emission current modulation with high current density at low operating voltages is achieved. A systematic analysis based on modified Fowler-Nordheim theory is used to analyze gate modulated VFE characteristics, confirming the triode field emission mechanism and operating principle. The realization of an efficient VFE microtriode has achieved the fundamental step for further development of vacuum integrated microelectronics.

Field effect controlled lateral field emission triode

Lateral field emission transistors show promise for many high frequency and high power applications. Typical lateral devices place a gate roughly in between the cathode tip and the anode. While effective, such devices require large gate voltages for device control. This study proposes relocating the gate on top of the semiconductor cathode stem, behind its emitting tip, allowing field effect transistor based control of the transistor. Both enhancement and depletion mode are possible, and the gate bias range needed for control becomes an easily designed parameter. Example structures are modeled where this range is about 1 V. Relocation of the gate has the additional benefit of simplifying the region between the anode and the cathode tip, thus opening up the possibility of shrinking their spacing.

Characteristics of a Triode Field Emission Display Panel with the Suspension Gate Structure

With the effective screen-printing technique and high-temperature sintering process, the suspersion gate structure was developed. The silver slurry was printed on the gate substrate to form the gate electrode. Using carbon nanotube as cold field emitter, the triode field emission display (FED) panel was fabricated, and the detailed manufacture process was also presented. The anode back plane, the cathode back plane and spacer combined to device room, in which the suspension gate structure would be included. The distance between the gate electrode and carbon nanotube cathode could be reduced, which could decrease the device manufacture cost because of the small gate voltage. The modulation of emitted electron by the gate voltage would be confirmed, and the field emission characteristics was measured. The sealed FED panel with simple fabrication process and designed structure possessed better field emission uniformity, high display brightness and field emission perofrmance.

Vacuum field-emission triode based on electron multiplier concentrator

The design and technology of manufacturing a vacuum field-emission triode (VFT) based on an electron multiplier concentrator that plays the role of a field-emission cathode capable of ensuring a significantly greater current density as compared to that provided by the other existing electron emitters. Experimental current-voltage characteristics of the VFT are presented. The possibility of creating integrated circuits based on the proposed device is discussed.

High-current, low-cost field emission triode using a reticulated vitreous carbon cathode

A simple, macroscale field-emission triode was assembled using a single 3.8 mm diameter Ar+-ion irradiated reticulated vitreous carbon (RVC) cathode. The irradiation process results in random carbon nanostructures on the surface of the RVC, providing effective, low-field emission sites. The use of RVC results in a self-ballasting cathode. The grid electrode further increases local field enhancement on the cathode surface, increasing the extracted current over what is produced in diode mode. The anode electric field required to produce 0.1 μA/cm2 was measured to decrease from 0.9 to 0.65 V/μm with 300 V applied to the grid electrode. With 2.1 V/μm, and 300 V applied to the grid, the limits of our power supply were reached, and a current density of 16.0 mA/cm2 and a current of 1.82 mA from a single cathode were measured. Semiconductorlike emission properties, showing three regions of operation, were observed. In region III the cathode emits from a large number of sites, producing a total beam that is readily focused to a small spot size with ordinary electron optics. This low-cost, robust configuration, machined without microfabrication processes or lithography, makes very-high total current in single field-emission triodes possible.

Flexible field emitter arrays with adjustable carbon nanotube distances and bundle generation

A template assisted technique was used to synthesize carbon nanotubes (CNTs) in a highly ordered manner by a noncatalytic chemical vapor deposition technique. Special self-organized anodic alumina films control the syntheses of highly aligned carbon nanotube arrays with desired tube geometry, adjustable intertube distances, and unique CNT bundle generation, which are extremely important for CNT array optimization with high field enhancement factors and high current densities. These CNT arrays also meet industrial demands such as uniformity, low cost, and easy preparation. The CNT bundle generation was adjusted by the CNT tube-diameter, wall-thickness, and length-controlled growth. Field emission tests showed that the turn-on field of the CNT cathode arrays could be lowered by adjusting the intertube distance. A vacuum field emission triode with self-aligned gate using these CNT arrays as field emitter is also presented. The proposed CNT configuration allows the realization of cathode arrays on flexible su...

Electron emission from nanometric apertures in CNTs-based field emission triode structures on silicon substrates

In this paper, we report a simple analytical model for carbon nanotube (CNT) based electron emitters and triode field emission devices on silicon substrates. Carbon nano-tubes have been grown in a direct current plasma enhanced chemical vapour deposition (dc PECVD) reactor from Ni catalyst islands. CNTs are electrically isolated by a TiO2 film and a chromium layer acts as the metal gate. The effects of the surrounding gate as well as the current–voltage behavior are investigated. To verify the experimental results of this structure a theoretical model is developed, using the Fowler–Nordheim tunneling effect combined with the electrodynamics theory. With certain simplifying assumptions, we replace the complex structure of triode devices with a simple structure which arrives at a closed formulation to predict field emission properties. Field enhancement factor is an important factor that depends on the CNT shape, gate opening and the applied voltage. In our fabrication process, the gate opening diameter can be of the order of the CNT diameter. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Field Emission Stability of Anodic Aluminum Oxide Carbon Nanotube Field Emitter in the Triode Structure

In this work, fabricated field emission (FE) triode arrays with the anodic aluminum oxide (AAO) template carbon nanotube (CNTs) as the field emitters are numerically analyzed. To obtain physically sound self-consistent solution, a set of Maxwell's equations coupling with Lorentz equation are solved simultaneously using a finite difference time domain particle-in-cell method. The FE current is then computed with the Fowler-Nordheim equation. To validate the simulation model, we firstly calibrate the collected electron current density between the measured AAO-CNTs and calculated result. The FE current is dominated by, such as density, height, diameter, and tilt angle of CNTs, and applied bias, respectively. A high density of CNTs will result in strong screening effect among adjacent CNTs and reduce the magnitude of electric field. Consequently, it significantly affects the emitted and collected electron current densities. However, the structure with much higher density of CNTs obviously emits more stable current than that of a low density of CNTs. There is an optimal setting on the height and diameter of the CNTs within the explored structure which exhibits the highest current density. When we vary the density of CNTs, the structure with high density (say the number of CNTs is greater than 30) shows the most stable and smallest fluctuation on the current density against the randomly generated samples of the height and tilt angle of CNTs.