Surface Conduction Electron Emitter Research Articles

Fabrication and field emission characteristics of surface-conduction electron-emission with ZnO nanorods based on planar-gate

In this paper, surface-conduction field emission (SCFE) device based on planar-gate triode with in-situ grown ZnO nanorods as the emitter has been fabricated. The ZnO nanorods are controlled to orientable grow by thermal evaporation on a substrate, and their microstructures are analyzed through XRD and SEM. The results show that the one-dimensional ZnO nanorods were rod-shaped, up to 200 nm in diameter and approximately 15 μm in length. They are of oriental growth, uniform in size and perpendicular to the substrate. With the screen-printing, a planar-gate surface conduction device is fabricated, and its field emission characteristics are tested. The test results indicate that the threshold voltage of the planar-gate ZnO-SCFE device decreases with the increase of the anode voltage. When the gate voltage is 62 V, the electron emission efficiency of the device is 36.1%, higher than the reported surface emission display (SED) emission efficiency. Besides, the proposed device has good modulated effect and stability, indicating that it is of good field emission characteristics.

Direction-division multiplexed holographic free-electron-driven light sources

We report on a free-electron-driven light source with a controllable direction of emission. The source comprises a microscopic array of plasmonic surface-relief holographic domains, each tailored to direct electron-induced light emission at a selected wavelength into a collimated beam in a prescribed direction. The direction-division multiplexed source is tested by driving it with the 30 kV electron beam of a scanning electron microscope: light emission, at a wavelength of 800 nm in the present case, is switched among different output angles by micron-scale repositioning of the electron injection point among domains. Such sources, with directional switching/tuning possible at picosecond timescales, may be applied to field-emission and surface-conduction electron-emission display technologies, optical multiplexing, and charged-particle-beam position metrology.

Giant Enhancement of Cathodoluminescence of Monolayer Transitional Metal Dichalcogenides Semiconductors.

Monolayer two-dimensional transitional metal dichalcogenides, such as MoS2, WS2, and WSe2, are direct band gap semiconductors with large exciton binding energy. They attract growing attentions for optoelectronic applications including solar cells, photodetectors, light-emitting diodes and phototransistors, capacitive energy storage, photodynamic cancer therapy, and sensing on flexible platforms. While light-induced luminescence has been widely studied, luminescence induced by injection of free electrons could promise another important applications of these new materials. However, cathodoluminescence is inefficient due to the low cross-section of the electron-hole creating process in the monolayers. Here for the first time we show that cathodoluminescence of monolayer chalcogenide semiconductors can be evidently observed in a van der Waals heterostructure when the monolayer semiconductor is sandwiched between layers of hexagonal boron nitride (hBN) with higher energy gap. The emission intensity shows a strong dependence on the thicknesses of surrounding layers and the enhancement factor is more than 500-fold. Strain-induced exciton peak shift in the suspended heterostructure is also investigated by the cathodoluminescence spectroscopy. Our results demonstrate that MoS2, WS2, and WSe2 could be promising cathodoluminescent materials for applications in single-photon emitters, high-energy particle detectors, transmission electron microscope displays, surface-conduction electron-emitter, and field emission display technologies.

Vacuum field-effect transistor with a deep submicron channel fabricated by electro-forming

Vacuum field-effect transistors (VFETs) with channel lengths down to 500nm (i.e., the deep submicron scale) were fabricated with the mature technology of the surface conduction electron emitter fabrication process in our former experiments. The vacuum channel of this new VFET was generated by using the electro-forming process. During electro-forming, the joule heat cracks the conductive film and then generates the submicron scale gap that serves as the vacuum channel. The gap separates the conductive film into two plane-to-plane electrodes, which serve as a source (cathode) electrode and a drain (anode) electrode of the VFET, respectively. Experimental results reveal that the fabricated device demonstrates a clear triode behavior of the gate modulation. Fowler-Nordheim theory was used to analyze the electron emission mechanism and operating principle of the device.

Surface-conduction electron-emitter characteristics and fabrication based on vertically aligned carbon nanotube arrays

The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. Vertically aligned CNT arrays with a delta-star arrangement were patterned and synthesized onto a quartz substrate using photolithography and thermal chemical vapor deposition. Delta-star shaped VACNT arrays with 20° tips are used as cathodes that easily emit electrons because of their high electrical field gradient. In order to improve the field emission and secondary electrons (SEs) in SCE applications, magnesium oxide (MgO) nanostructures were coated onto the VACNT arrays to promote the surface-conduction electron-emitter display (SED) efficiency (η). According to the definition of η in SCE applications, in this study, the η was stably maintained in the 75–85% range. The proposed design provides a facile new method for developing SED applications.

Numerical analysis of the surface-conduction electron-emitter with a new configuration

A new kind of surface-conduction electron-emitter (SCE) with a triangular dielectric layer under the conductive film is proposed. The influences of the vertex angle [Formula: see text] of the triangular dielectric layer and the anode voltage [Formula: see text] on the electron emission efficiency and the focusing capability have been investigated with the finite integration technique (FIT). The numerical simulation results show that SCE with a small vertex angle guarantees higher electron emission efficiency even with a low anode voltage. But the focusing capability of the electron emitter will get worse when the [Formula: see text] or [Formula: see text] becomes too small. Take both the electron emission efficiency and focusing capability into consideration, the structure with a vertex angle [Formula: see text] between [Formula: see text]–[Formula: see text] and the anode voltage of 1500[Formula: see text]V is suggested.

Analysis of the influence of nanofissure morphology on the performance of surface-conduction electron emitters

A simulation model was built to numerically investigate the electron emission property of a new surface-conduction electron emitter (SCE) with a raised emitter structure. The model calculated the electric field distribution, the electron emission characteristics, and the electron trajectories, which were useful for analyzing and understanding the microscopic mechanism of the electron emissions of the new SCE structure. It was found that the new structure increased the probability of electrons being collected by the anode which led to an increase of the anode current despite of the decrease of field emission current. This study benefits the advanced design of emitter structures in nanoscale technology for new types of electron sources.

Mechanism of the activation process for the formation of a surface-conduction electron-emitter

The major role of the chemical reaction between a silica substrate and deposited carbon in the activation process for the formation of a surface-conduction electron emitter (SCE) is investigated. The SCE emits electrons by the tunneling effect when an electric field is applied across a nanoscale gap. The nanogap is spontaneously formed by the activation process, wherein a pulse voltage is applied between a pair of electrodes, which are separated by a narrow gap inside a vacuum chamber in the presence of hydrocarbons. At the gap, two elemental processes compete; the deposition of carbon by the electron-induced decomposition of hydrocarbons and the consumption of carbon by reaction with the silica substrate. The balance of the dynamics of the two processes, which simply depends on the temperature at the gap, is responsible for the spontaneous determination of the width of the nanogap. The calculation based on the model that involves the two competitive processes agrees with the experimental results on the activation process.

A new structure for improving the uniformity and electron emission efficiency of surface conduction electron emitters

A surface-conduction electron-emitter (SCE) with a raised structure in the middle of the conductive film is proposed in this paper. With this new structure, the formation position of the nanoscale fissure can be controlled easily during the electro-forming process, and this will help to improve the uniformity of SCEs. In contrast to typical methods of SCE preparation, a SiO2 strip layer is deposited in the middle of the electrode gap before the conductive film is sputtered. The conductive film over the SiO2 strip can accumulate more joule heat during the electro-forming process, and this subsequently causes the nanoscale fissure to be formed at the region along the step area of the SiO2 film and conductive film. Experiment results reveal that the new structure increases electron emission efficiency from 0.191% to 0.779%.

A graphene-based large area surface-conduction electron emission display

The fabrication and functionality of a 21cm graphene-based transverse electron emission display panel is presented. A screen-printed triode edge electron emission geometry has been developed based on chemical vapor deposited (CVD) graphene supported on vertically aligned carbon nanotubes (CNT) necessary to minimize electrostatic shielding induced by the proximal bulk substrate. Integrated ZnO tetrapod electron scatterers have been shown to increase the emission efficiency by more than 90%. Simulated electron trajectories validate the observed emission characteristics with driving voltages less than 60V. Fabricated display panels have shown real-time video capabilities that are hysteresis free (<0.2%), have extremely stable lifetimes (<3% variation over 10h continuous operation) in addition to rapid temporal responses (<1ms).

颗粒膜厚度对表面传导电子发射的影响

颗粒膜厚度对表面传导电子发射的影响

阴极形貌对表面传导电子源的影响

The influence of the cathode structure on the distribution of electric field near the cathode and grid,and the emission electron trajectories near the intersection of the cathode,film and vacuum is studied in surface-conduction electron emitter by the finite elements method.The results indicate that not all electrons emitted from the zone near the intersection can reach the anode through analyzing electron trajectories.The anode voltage,the cathode height and the cathode shape affect the position from which electrons emit and can reach the anode thereby affecting the efficiency of electron emission,simulation shows that reducing the electrode height,increasing anode voltage and applying arc electrode of large radius can increase electron emission.

Alternate lightening display method for surface-conduction electron-emission display

Alternate Lightening Display Method (ALDM) for surface-conduction electron-emission display (SED) is proposed to help cutting down the panel fabrication cost. Since the landing position of the emitted electrons on the phosphor plate is mainly determined by the polarity of the device voltage and close to the positive voltage electrode, the same dynamic resolution can be obtained by ALDM with only half surface-conduction electron-emitters (SCEs) compared with the conventional panel. The experiment shows six luminescence lines can be generated with three SCE lines. The emitted electron excursion on the phosphor plate is analyzed with a simplified model, and it is in good agreement with the experiment result.

Microstructural and Electron-Emission Characteristics of Nb-Si-N Films in Surface-Conduction Electron-Emitter Display

Abstract We proposed ternary nitride Nb-Si-N film as a promising surface-conduction electron emitter (SCE) in surface-conduction electron-emitter display (SED). Nb-Si-N films consisted of continuous NbN polycrystalline phase with (Si3-xNb4x)N4 amorphous phase in NbN grain boundaries. After electroforming, serrated nanogaps were observed in Nb-Si-N SCE strips. The emission current of Nb-Si-N SCE array of 1×18 cells was 6.50 μA with anode voltage of 1.5 kV and device voltage of 22 V, indicating satisfying potential for display applications comparing with NbN SCEs. © 2009 Published by Elsevier B.V.

Thermal Stress Induce Formation Nanogaps in Surface Conduction Electron Emitter

Abstract The different thermal stress in multilayer thin films during heating or freezing process can be employed to form the different morphologies: wrinkle, buckle, and crack. In this paper, a simple process based on above method is explored to induce and control Pd film to crack or delamination with crack which can be used as excellent electrode of surface conduction electron emitter. The crack size in Pd film can be limited into the range of 10 nm to 1.3 μm when the freezing time changes from 1 to 120 seconds. The cracks can also be achieved on the top of delaminate or buckles in Pd film by increasing temperature from room environment to 120°C. The crack position is promoted from 0 to tens microns and the crack angle adjusted from 0 to ∼ 60 degrees. Comparing the field emission characteristics of the different structured nano-gaps (plane crack and delaminating crack), larger crack angle is more conductive to tunneling electrons scatting out and the promoted electrodes decrease the distance between cathode-anode electrodes of electron emission. With the experiments of current-voltage properties of conducting mechanisms on a prototype device of surface conduction electron emitter, it is observed that the power consumption from cracks followed the delaminating process is remarkably lower than the simple plane cracks.

Surface-Conduction Electron-Emitter in Granular Films

Abstract There are much more obstacles to prevent the commercialization of Surface-conduction Electron-emission Display (SED) as a kind of best potential field emission display. Less effort, however, has been made to develop crucial SED emitter materials. So we suggested the granular films serve as SED emitters and proposed the details of why to select granular films and how to constitute granular films. Furthermore, the four rulers about how to constitute granular films were supposed as following: (a) forming the mixture, (b) different showing giant different physical/chemical properties, (c) one of composition showing low work function and stability, and (d) feasibility of deposition process. Basing on these rulers, the Ti-DLC and Al-AlN granular films were optimally selected as SED emitter materials and the prototype devices in using these two granular films were all fabricated. By comparing with electric properties of other materials SED emitter, our results proved that the granular film was a potential SED emitter material with low turn-on voltage of 10.5 V for Al-AlN granular films and 11.5 V for Ti-DLC granular films and low driving current of each unit (or sub-pixel) of 0.17-0.22 mA for Al-AlN granular films and 0.11-0.17 mA for Ti- DLC granular films.

W-Si-N Nan-Crystal as Electron Emitter Applied in SED

Abstract As the most potential next-generation display technology, SED(Surface-conduction Electron-emitter Display) whose independent electron emission character and good image quality draw much attention. Because of the higher emission efficiency than ZnO or PdO in the same craftwork, W-Si-N was selected as electron emitter material applied in SED. In this work, we developed SED with W-Si-N electron emitter film through magnetron sputtering and photoetching technology. We have found that W-Si-N thin film has high luminescent performance. WN and Si3N4 were found in W-Si-N film according to the results of XRD (X-Ray Diffraction) and XPS (X-ray photoelectron spectroscopy). Moreover, the obvious negative resistance effect based on the electron tunneling was observed in the nano-gap formulating process. Crystal boundary, defects, and impure particle affect electron emission efficiency. Besides, we have investigated the fabricating parameters, crystal structure and electron emitting characteristics and obtained the highest emission efficiency∼4.3%.

Electroforming characteristics of SED emitter in Al-AlN granular films

The Al-AlN granular film was proposed as a cathode emitter of surface-conduction electron-emission display (SED) and the effect of Al-AlN granular films’ resistivity on electroforming in experiment and simulation methods was studied. Electroforming could be successfully completed with appropriate Al-AlN granular film resistivity between 1.98 and 15.10 mΩ·cm, and the corresponding turn-on voltage of electroforming increased from 6.2 to 10.5 V with the resistivity increasing. In addition, a temperature profile on Al-AlN emitter was simulated and the temperature decreased from middle to two sides, which were corresponding to surface morphology of Al-AlN emitter after electroforming.

Electron Emission Properties of Surface-Conduction Electron Emitters With a PdO-C-PdO Multilayer Conductive Film Deposited by Magnetron Sputtering

Conductive films are an essential component in surface-conduction electron emitters (SCEs), and they have a major influence on the electron emission properties of SCEs. In this work, a novel PdO-C-PdO multilayer film deposited by magnetron sputtering is proposed as the conductive film in SCEs. Three SCE cathodes with this type of multilayer film were fabricated, together with three other SCE cathodes with a PdO single-layer film used as a reference. For these cathodes, the dependences of the conduction current and the emission current on the device voltage and the anode voltage were measured, and the luminescence patterns were observed after the electroforming and activation processes of the conductive films had occurred. The surface morphologies of the conductive films were analyzed by scanning electron microscopy. The results indicate that the SCEs with the PdO-C-PdO multilayer conductive film have better electron emission properties compared with the SCEs with the PdO single-layer conductive film. For an anode voltage of 2 kV and a device voltage of 14 V, the emission current and the electron emission ratio of the SCEs with the PdO-C-PdO multilayer film can reach 179.5 μA and 2.2‰, respectively.

Thermal shock induced nanocrack as high efficiency surface conduction electron emitter

Significant emission current enhancement has been achieved for surface conduction electron emitter, due to the special three-dimensional nanocrack structure fabricated by the thermal shock process. The three-dimensional configuration strongly changed the electric field distribution and controlled the emission electron trajectory. Thermal shock treatment was also used to increase the edge roughness of the nanocrack and thereby dramatically improved the field emission characteristics. Stable and uniform electron emission was observed with turn-on voltage of 150 V. The surface conduction current of 400 μA for 6 cells was obtained with the detector voltage of 1 kV and the gap voltage of 170 V.