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Volcano-structured double-gated field emitter arrays (VDG-FEAs) with different focusing electrode height have been fabricated and the focusing characteristics for each VDG-FEAs were evaluated in detail. The authors experimentally proved that lowering the focusing electrode was very effective to keep a high emission current and successfully removed the electric field relaxation at the tip during the focusing operation. The anode current of about 1.9μA was maintained for the VDG-FEA with the height of the focusing electrode relative to the extraction electrode, hf=−470nm, even in applying 5V to the focusing electrode, and the current was 84.4 times larger, compared with the sample with hf=220nm under the same focusing condition. It was found that the emitted electrons returned back to the extraction electrode by the potential barrier caused by the low focusing potential below 3V in every sample.

The authors have demonstrated the novel CdTe x-ray imaging device that consists of a Schottky CdTe diode and a 12×12 matrix-structured field emitter array (FEA). The Schottky CdTe diode was fabricated by depositing In on a Cl-doped p-type (π-type) CdTe substrate and Sb2S3 on the opposite side of the CdTe substrate. The matrix-structured FEA was fabricated by reactive ion etching and etch-back method. The output current was successfully detected by the recombination of holes with electrons from the FEA, and clearly depended on the x-ray intensity.

An ultrahigh-luminance field-emission display (FED) is designed in which a field emitter array (FEA) and memory function are integrated in every pixel of the display panel. The memory function consists of an emission-control thin-film transistor (TFT), a memory capacitor, a write-enable TFT, and a memory-discharging TFT. The operation mechanism is that the time of luminance of the pixel is made longer by the memory function; thus, luminance becomes higher. In principle, the maximum luminance of such a display is expected to be more than 100 000 cd/m2. The ultrahigh-luminance FED is applicable for daylight-readable displays used in mobile electronic equipment. The authors fabricated a prototype of the ultrahigh-luminance FED using Spindt-type FEA and poly-Si TFT technology. It was confirmed that the luminance of the display panel is controlled by the signal for the memory-discharging TFT, which means that the luminance can be dynamically controlled by the input signal. The maximum luminance of 1700 cd/m2 was achieved at a relatively low anode voltage of 1.5 kV. The higher luminance can be expected by applying higher anode voltage.An ultrahigh-luminance field-emission display (FED) is designed in which a field emitter array (FEA) and memory function are integrated in every pixel of the display panel. The memory function consists of an emission-control thin-film transistor (TFT), a memory capacitor, a write-enable TFT, and a memory-discharging TFT. The operation mechanism is that the time of luminance of the pixel is made longer by the memory function; thus, luminance becomes higher. In principle, the maximum luminance of such a display is expected to be more than 100 000 cd/m2. The ultrahigh-luminance FED is applicable for daylight-readable displays used in mobile electronic equipment. The authors fabricated a prototype of the ultrahigh-luminance FED using Spindt-type FEA and poly-Si TFT technology. It was confirmed that the luminance of the display panel is controlled by the signal for the memory-discharging TFT, which means that the luminance can be dynamically controlled by the input signal. The maximum luminance of 1700 cd/m2 w...

The ion-induced-bending (IIB) phenomenon was applied for fabricating a field-emitter array (FEA). The IIB method can form a vertical-thin-film (VTF) structure with micron-order height and a high aspect ratio from a thin film. Accordingly, it only needs small quantities of material and uses no specialized equipment. As a result of the optimization of the IIB phenomenon, the apex radius of the VTF was decreased by decreasing the film thickness. The material dependence of the IIB method was investigated, and the authors found that the molybdenum film gives the largest bending angle of the three refractory metals tested. An emission current of 10μA from the Mo-VTF emitter with 1000 tips was obtained at relatively low extraction voltage. Then thus conclude that IIB is a very promising method for fabricating a FEA.

As the state of the art, ion implantation techniques require high-current ion beams with the lower energy, as the dimension of the devices becomes smaller. However, it is difficult to drive the lower-energy ion beams straightly, due to the huge ionic space charge. We proposed utilization of electron beam emitted from silicon field emitter arrays (Si-FEA) for compensation of the ionic positive space charge. One of the difficulties in utilizing Si-FEAs in ion implanter is such that the Si-FEA is easily affected by the residual gases, since the implantation generates gas molecules from photoresist materials. It is shown that the emission current decreases, especially in oxygen. One of the ways to protect the surface from oxidation is deposition of the material, which is highly resistant against oxidation, to the tip surface. We modified the surface of the Si-FEA by carbon negative ion implantation, in order to protect the surface from oxidation. In this paper we show the effectiveness of the carbon negative ion implantation to extend the lifetime of Si-FEAs.

By adding a memory function to each pixel of a field emission display (FED), an ultrahigh luminance FED with a luminance of more than 10000cd∕m2 can be realized. For this purpose, the authors fabricated a field emitter array (FEA) with a memory function, in which a FEA, emission-control thin-film transistor (TFT), memory capacitor, and write-control TFT are monolithically integrated. They used an HfC-coated Si tip for the FEA because it enables a long emission lifetime. The TFT structure was optimized to control the emission current. The memory-function FEA was demonstrated in a vacuum chamber. The data holding time of the memory function was also measured. It was sufficiently long for display applications.

The HfC-coated Si field emitter arrays (FEAs) controlled by built-in poly-Si thin-film transistors (TFTs) were fabricated. The FEAs were fabricated at a relatively low temperature using Ar-ion-sputter sharpening so that a low-temperature poly-Si TFT process can be applied. A HfC thin film was coated on emitting tips for improving emission lifetime. An emission control TFT having a conventional top-gate structure was fabricated using ion implantation and activation annealing. A combination of multigate and lightly doped drain (LDD) structures was effective at reducing leakage current at a high source-drain voltage. We fabricated a HfC FEA integrated with a TFT having four gate electrodes with a LDD structure. Complete control of FEA emission current by built-in TFT was demonstrated in a vacuum chamber. The detailed fabrication process and emission control characteristics are reported.

We have already reported superior characteristics of field emission from hafnium carbide (HfC)-coated Si field emission arrays. To clarify the microscopic feature of HfC films related to electron emission, the topograph and local work function (LWF) of the HfC film deposited on Si(100) substrates are examined in an atomic scale by using scanning tunneling microscopy (STM). From the STM/LWF images of the sputtering-cleaned film, it is revealed that the HfC film consists of grains with about 10 nm in size, and that the surface stoichiometry at the grain boundaries becomes carbon rich due to preferential sputtering after higher energy argon ion sputtering.

Field emission arrays (FEAs) comprising 100 Si or HfC coated Si emitters have been fabricated. The FEAs emission properties were measured in ultra high vacuum conditions and after being subject to Ar and O2 residual gases with partial pressures in the range 10−6 to 10−4Pa. The influence of residual gases on the FEAs field emission properties has been comparatively assessed using the model parameter extraction method. The array field emission model uses equations that describe the electron emission current from individual emitters of given radius R and work function ϕ together with nonuniform distribution functions giving the dispersion of these parameters within the array. A simplified relationship for the array emission current depending on a single integral instead of a double one has been derived. A nonlinear extraction algorithm using partial derivatives of the objective function is used, which gives fast and accurate results. Both Si and HfC emitters exhibit (to a different degree) tightening of the ...

The article presents a quantum mechanical model for the electron field emission from semiconductor surfaces covered by dielectric layers. By systematically connecting electronic wave functions at various interfaces, the model obtains in a unified manner the field emission current density from both clean and dielectric-covered semiconductor substrates. No energy quantization is imposed for the interface layer and thermodynamic nonequilibrium is allowed between the conduction electrons from the interface (accumulation) layer and those of the bulk. The model is applied to study the electron field emission from Si tips covered by ultrathin oxide layers and also to explain the resonance effects observed in field emission from Si covered by thicker dielectric layers.

We propose a metal–oxide–semiconductor field-effect transistor (MOSFET)-structured Si field emitter array (FEA) with a ring gate FET. A ring-shaped MOSFET gate electrode surrounds the Si FEA and this electrode plays two roles. The first is to control the emission current, and the other is to focus the electron beam emitted from the FEA. The emission current can be controlled by the voltage of the ring gate. We evaluated focusing properties of the ring gate FET structured Si FEA by observing the emission patterns on an anode phosphor screen. The detailed electron trajectory simulation qualitatively agreed with the experimental results. The simulation revealed that the new device has better focusing properties than a conventional FEA with an in-plane lens electrode.

The traditional approach of analyzing field emission (FE) data using the “emission area” and “field enhancement” factors is faulty. Instead, the emission current I should be computed through integration of the tunneling current density over the emitter surface, taking into account the local variation of the electric field. As a consequence, FE data represented as Fowler–Nordheim (FN) plots ln(I/V2) versus 1/V are nonlinear regardless of the model used to derive the electric field and the modified FN plot ln(I/V3) versus 1/V is more suitable for representing the FE data in a linear way. In this article, a general approach for extraction of model parameters using wide-range FE data is proposed. A nonlinear least-square fitting procedure is applied to emission data based on the statistical gated emitter/triode model tailored for the particular emitter configuration. Uniform distributions for the emitter radius R and work function φ in the array are considered, although other distributions may be included in ...

The emission uniformity of Si field emitter arrays (FEAs) with 1024 tips were evaluated by using electrostatic lens projector. Some surface modifications were applied to the Si FEA for improving the emission uniformity. A combination of CHF3 plasma and preheat treatments is very effective for cleaning the tip surface and for improving the uniformity of the work function distribution in the array. The number of working tips increased by a factor of 5 after the preheat treatment at the temperature of 450 °C. For further improvement, high current pulses were applied to the FEA. The pulse drive is effective for improving the uniformity of the tip radius. By applying all of the treatment and driving methods, more than half of the array emitters could be activated even for small operating current of 5 μA.

We fabricated hafnium carbide (HfC) coated Si field emitter arrays (HfC FEAs) with an extraction-gate electrode to improve the emission characteristics of Si FEAs. Hafnium carbide thin film was deposited by inductively coupled plasma-assisted magnetron sputtering. The HfC film was characterized by x-ray photoelectron spectroscopy and x-ray diffraction measurement, and was found to be (111)-oriented polycrystalline film. The HfC FEAs exhibited superior performance. An emission of more than 10 mA could be obtained from the 16 000 tip array, which is 20 times higher than that for Si FEAs. The operational voltage for emission of 1 μA decreased from 61 to 45 V due to the HfC coating. The long-term emission characteristics were also measured. Si FEAs degraded rapidly even in an ultrahigh vacuum chamber. However, the emission degradation in the HfC FEAs was much slower. The number of active tips was counted using an electrostatic-lens projector, and the results revealed that the HfC FEAs had six times as many ti...

A novel silicon nanowire with programmable conductivity which utilizes sensitivity of conductance to surface charging has been investigated. The device consists of a nanowire with a width of 10–25 nm and side gates for control of surface charging on to the nanowire. The wire current measured during sweep of the side gate exhibited clear hysteresis characteristics and significant retention of the programmed states for more than 1000 s. Surface potential imaging of the nanowire by means of scanning Maxwell-stress microscopy (SMM) has been carried out for correlating the programmed conductivity to charging on the nanowire. The SMM images clearly exhibited that charging on the nanowire which provided the programmable conductivity was precisely controlled by the side gate sweep.

Si field emitter arrays (FEAs) were monolithically integrated with metal–oxide–semiconductor field-effect-transistor (MOSFET) based driving circuits on a Si chip for the first step toward developing the field-emission-display-on-a-chip (FED-on-a-chip), which is a candidate for the next-generation FED. We developed a fabrication process of Si FEAs integrated with MOSFET driving circuits. A 4×4 matrix Si FEA, emission-control MOSFET, and simple driving circuits consisting of a shift register were integrated on the same chip. The operation of each element, such as MOSFET-controlled Si FEAs and logic circuits for the driver, was confirmed. The emission current from the Si FEA can be controlled by the built-in MOSFET at a voltage of less than 5 V, which can be driven by the built-in driving circuits. The operation of the 4×4 matrix FEA with driving circuits was demonstrated. This is the first operation of the FEA integrated with MOSFET logic circuits. The detailed design and fabrication processes are described.

Emission uniformity improvement of a silicon field emitter array (FEA) by ethylene (C2H4) gas exposure has been investigated in detail especially about its origin. Scanning Maxwell-stress microscopy has been utilized to evaluate the surface potential at the Si tip apex in the FEA before and after the improvement. Careful consideration to eliminate the influence of the surrounding gate has been made in order to estimate work function at the tip apex. It has been found that the work function at the tip apex decreased upon C2H4 exposure. It has been clarified that the uniformity improvement by C2H4 exposure is mainly due to the reduction in the tip work function.

Surface modification of Si field emitters by CHF3 plasma is investigated for damageless vacuum sealing. The emission characteristics of nontreated Si field emitters and CHF3-plasma-treated Si field emitters were measured in an ultra-high-vacuum chamber and in a frit-sealed vacuum package. The vacuum sealing process decreased the emission currents from the nontreated Si field emitters by a factor of 10. On the contrary, the emission current from the CHF3-plasma-treated emitters did not change before and after the vacuum sealing process. Analysis by Auger electron spectroscopy and by x-ray photoelectron spectroscopy revealed that the CHF3-plasma-exposed Si surface was covered with SiC and fluorocarbon films. These carbon-related films work as a protective material in the sealing process. By using this method, we achieved the first operation of metal–oxide–semiconductor field-effect-transistor-structured Si field emitters in a vacuum package.

We have examined endurance of Spindt-type field emitter arrays (FEAs) against oxygen ambient. In this study, the endurance of four different emitter materials, Ni, Pt, Au, and Mo was investigated. The electron emission characteristics of FEAs with 1 to 1600 tips were measured in ultrahigh vacuum (UHV) and in oxygen ambient. For all the FEAs, the emission current decreased with an increase in oxygen pressure. Some of the emitters were destructed during the emission test in oxygen ambient. The detailed analyses of the emission characteristics were performed by calculating the noise power and observing the emission pattern on the phosphor screen. The noise power increased with an increase in oxygen pressure. Emission pattern on the phosphor screen showed enlarged emission area, as compared with the pattern obtained in UHV. The present results indicated that even the Pt emitters were affected by the ambient oxygen. The elimination of oxygen is the essential subject for the development of field emission display.

We fabricated NbNx thin-film field emitter arrays by the ion beam assisted deposition technique which can prepare transition-metal nitride thin films at a relatively low temperature of about 500 °C. The emitter arrays were fabricated by depositing NbNx thin films on Si cones. The nitrogen composition of the film is controlled by selecting the deposition condition, such as the arrival rate ratio of N to Nb flux. We investigated the influence of the nitrogen composition of the NbNx thin-film field emitter arrays on electron emission characteristics. The emitter arrays with a higher nitrogen composition emitted electrons at a lower voltage and showed more stable emission than those with a lower composition. We compared the emission stability of the NbNx emitters with that of the Si emitters. The emission from the NbN emitter (composition ∼1.0) was more stable than that from the Si emitter by a factor of 10 in terms of the noise power.

ZrN thin film field emitter arrays were fabricated by the ion beam assisted deposition technique. The work function of ZrN is controlled by the selection of the deposition parameters. We investigated the relationship between the work function and the emission stability, and the influence of the ambient gas on the emission stability by introducing the gases of N2 and O2 into the measurement chamber. It was found that the emission stability depended on the work function: the emitters with a lower work function were more stable than those with a higher work function. The dependence is explained qualitatively by the analysis of the Fowler–Nordheim equation. Emission noise increased with the increase of the ambient gas pressure. However, difference in the increase of noise between N2 gas and O2 gas was seen. O2 gas severely affected the emission stability of the ZrN emitter.

We have proposed a cone-shaped metal-insulator-semiconductor cathode (COSMISC) to improve the emission efficiency of the conventional metal-insulator-semiconductor cathode. This cathode is also recognized as the field emitter with prior electron acceleration mechanism. Since the COSMISC emits the electrons with higher energy than those at the Fermi level of the metal electrode, it is expected that the current fluctuation due to the change in work function of the metal electrode is less significant than that of a conventional field emitter. In this article, we analyzed the emission characteristics of the COSMISC in detail by Monte Carlo simulation, especially from the viewpoint of the emission stability against the change in work function of the upper metal electrode. The calculation procedure is as follows: electrons are generated according to their energy distribution at the semiconductor-insulator surface, and the scattering processes in the insulator and in the metal electrode were simulated with random numbers. Emission of electrons into vacuum was judged also according to the transmission probability at the surface barrier of the metal electrode. The obtained results are arranged with respect to the work function and also to the external field at the apex of the metal electrode. It was shown that the fluctuation of the emission current in COSMISC due to the change in work function is lower than that of the conventional field emitter.

In order to find out the cathode material suitable to vacuum microelectronics devices, dependence of cathode material of field emitters was investigated with respect to the emission characteristics. Since the field emitters for vacuum microelectronics devices are fabricated by thin film processes, the characteristics of the electron emission from deposited materials should be examined. In the present study, a dozen materials were deposited onto the tungsten needle fabricated by well‐controlled electrochemical etching. Measurement of the emission was performed at the pressure of 10−9 Torr range. The current–voltage characteristics and the stability measurements revealed that the gold emitters indicated excellent properties: stable and high current at low extraction voltage. The effective surface work function and the effective emission area were evaluated from the Fowler–Nordheim theory, assuming that the emission area rapidly decreases with reducing the apex radius. From this analysis, it is clarified that the gold emitter had the lowest effective work function among the examined emitters. The results can be interpreted as that in order to obtain stable emission characteristics, materials with inert surface should be selected.