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Highly efficient electron emission of 48.5% was demonstrated by a graphene/oxide/semiconductor (GOS) structure. The main factors contributing to this performance were investigated by analyzing the ...

In this work, a planar electron emission device based on a graphene/hexagonal boron nitride (h-BN)/n-Si heterostructure is fabricated to realize highly monochromatic electron emission from a flat surface. The h-BN layer is used as an insulating layer to suppress electron inelastic scattering within the planar electron emission device. The energy spread of the emission device using the h-BN insulating layer is 0.28 eV based on the full-width at half-maximum (FWHM), which is comparable to a conventional tungsten field emitter. The characteristic spectral shape of the electron energy distributions reflected the electron distribution in the conduction band of the n-Si substrate. The results indicate that the inelastic scattering of electrons at the insulating layer is drastically suppressed by the h-BN layer. Furthermore, the maximum emission current density reached 2.4 A/cm2, which is comparable to that of a conventional thermal cathode. Thus, the graphene/h-BN heterostructure is a promising material for planar electron emission devices to obtain a highly monochromatic electron beam and a high electron emission current density.

The planar type electron emission devices using atomic layered materials of graphene and hexagonal boron nitride (h-BN) were developed to suppress inelastic electron scattering within the device structure. High emission efficiency of more than 40 % and high emission current density of more than 100 mA/cm2 were achieved by the suppression of the inelastic electron scattering within the topmost gate electrode using graphene,. In addition, highly monochromatic electron emission with an energy spread of 0.18 eV in the full width at half maximum were realized by the suppression of the inelastic electron scattering within the topmost gate electrode and insulating layer using the graphene/h-BN heterostructure. These results would lead to several practical applications of planar type electron emission devices.

We propose the scanning electron microscope (SEM) using the graphene-oxide-semiconductor type planar electron emission device as an electron source. Graphene/Oxide/Semiconductor (GOS) structure realizes very high electron emission efficiency of over 30 % and it can be operated in low vacuum condition and low applied voltage. Therefore, SEM using the GOS electron source can eliminate several condenser lenses from the electron optics which are needed in the conventional SEM due to the very small divergence angle of the electron beams emitted from the flat surface. In this study, we installed the GOS type electron source into the conventional SEM and successfully obtained the stable SEM image with a probe current of 20 pA without noise using GOS electron source. In addition, we found the optimal electron optics for the parallel electron beams with a very small divergence angle of approximately 0 degree by the simulation of the electron beam trajectory.

A graphene-oxide-semiconductor (GOS) planar-type electron source is coated with a hexagonal boron nitride (h-BN) film to improve its oxidation resistance. The h-BN film is selected as a coating material owing to its high oxidation resistance and electron transmissivity. To evaluate oxygen resistance, the electron emission density versus applied gate voltage is measured before and after an atomic oxygen (AO) exposure for 4 minutes using an oxygen plasma asher. As a result, the device covered by h-BN emits electrons even after the AO exposure, indicating that the graphene electrode under the h-BN remains.

We previously reported highly monochromatic electron emission from the planar-type electron emission devices based on a graphene/hexagonal boron nitride (h-BN) heterostructure. In this paper, the electron energy distribution (EED) of these devices is examined to clarify the mechanism of monochromatic electron emission. We find that the monochromaticity of the electron beam depends significantly on the electronic structure of the substrate material; for the devices with an n-type silicon substrate, the narrowest FWHM of the electron beam is 0.18 eV, whereas that of devices with a metallic (Nb) substrate is 0.33 eV. At the same time, simulations considering the electron scattering by phonons acceptably reproduced the shape of each EED spectrum considering the small energy loss due to out-of-plane acoustic phonon modes in h-BN. Thus, the monochromatic electron emission from the $\mathrm{graphene}/h$-$\mathrm{BN}/n$-$\mathrm{Si}$ device is ascribed to a combination of the narrow energy distribution of electrons at the conduction band of the n-$\mathrm{Si}$ substrate and small phonon energy of the h-BN insulating layer. These features also realize the excellent emission properties in addition to the monochromaticity of the beam, such as a high emission current density of $9.3{\mathrm{A}/\mathrm{cm}}^{2}$, insensitivity to environmental pressure up to 10 Pa, and long lifetime of more than 7 days with little decay.

Electron emission properties of planar-type electron emission sources based on oxidized nanocrystalline silicon with graphene-gate electrode were investigated. The emission current was improved by an order of magnitude by vacuum annealing.

The digital type CMOS-MEMS cointegrated pressure sensor with a CMOS ring oscillator on a thin diaphragm was fabricated using cost-effective minimal-fab process and the successful operation of the fabricated pressure sensor was demonstrated, for the first time. It was confirmed that about 40 kHz difference in the oscillation frequency is observed in the fabricated CMOS-MEMS cointegrated pressure sensor chip by changing pressures from -40 to +40 kPa. This result is originated from the drain current variations of the longitudinal $ $ channel PMOSFETs of the CMOS ring oscillator owing to the piezoresistive effect. The developed CMOS-MEMS cointegrated pressure sensor is suitable for the application to the potable IoT sensor systems because it has a low-power consumption due to its all CMOS integration.

A graphene-oxide-semiconductor (GOS) planar-type electron source was fabricated by direct synthesis of graphene on an oxide layer via low-pressure chemical vapor deposition. It achieved a maximum electron emission efficiency of 32.1% by suppressing the electron inelastic scattering within the topmost gate electrode using a graphene electrode. In addition, an electron emission current density of 100 mA/cm^2 was observed at an electron emission efficiency of 16.2%. The electron energy spread was well fitted to Maxwell-Boltzmann distribution, which indicates that the emitted electrons are the thermally equilibrium state within the electron source. The full-width at half-maximum energy spread of the emitted electrons was approximately 1.1 eV. The electron emission efficiency did not deteriorate after more than 42 h of direct current operation. Thus, the GOS planar-type electron source has the potential to be an excellent electron gun for electron microscopy., This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in (https://aip.scitation.org/doi/10.1063/1.5091585) and may be found at [https://doi.org/10.1063/1.5091585].

In this study, we fabricated nano-capillary emitter arrays for stable ion emission of ionic liquid electrospray thrusters, employing the fabrication of field emitter arrays or gated nano electron sources. A nano-capillary emitter was successfully fabricated with a 100–300 nm capillary diameter, which prevented ionic liquid leakage by significantly increasing the fluidic impedance of the ionic liquid compared to a previously proposed emitter. An ion emission experiment was conducted with 1-ethyl-3-methylimidazolium dicyanamide as the propellant. Ion emission started at a low voltage of 61 V owing to a small gap of approximately 1 μm between the emitter and extractor electrode. The maximum current density was 43 mA cm−2 on the positive side and −13 mA cm−2 on the negative side without leakage of the ionic liquid, which was more than 100 times higher than that of conventional electrospray thrusters. Moreover, we obtained continuous ion emission without current intercepted by the extractor.

We have developed a highly sensitive, compact image sensor that comprises a field emitter array (FEA) and a high-gain avalanche-rushing amorphous photoconductor target, with the ultimate aim of developing an ultrahighly sensitive, compact, high-definition television camera. Double-gated FEs have an advantage of having a compact electron beam focusing system; however, image intensities reproduced by the sensor were nonuniform due to low electron beam current. Furthermore, the simulated electron beam current disagreed with the measured current. The electron beam current characteristics of two types of double-gated, Spindt-type FEs (both with improved electron beam current extraction) are discussed for possible use within the sensor: convex-structured and volcano-structured. A highly accurate simulation model of the image sensor using a double-gated, Spindt-type FE has been examined; the simulated electron beam currents extracted from the double-gated, Spindt-type FE are in agreement with the measured electron beam currents when the initial electron velocity is assumed, thus suggesting that the simulated anode current–anode voltage characteristic conforms to the measured one. For example, the electron beam currents extracted from the convex-structured and volcano-structured FEs when the focusing electrode is placed 0.2 $\mu \text{m}$ below the gate electrode opening at a focusing electrode voltage of 15 V are, respectively, 1.8 and 1.9 times larger than that extracted from the previously used FEs when the focusing electrode is stacked 1.5 $\mu \text{m}$ above the gate electrode. The results show potential for reducing the degradation of the uniformity of the reproduced image’s intensity, and show that the highly accurate simulation model of the sensor is valid to design the double-gated FEAs for the sensor.

The Minimal Fab concept was proposed in 2008 to produce low-volume customized devices with a low investment cost [1]. The different points of Minimal Fab compared with those of the conventional Mega Fab are as follows. (a) Wafer size is half-inch (12.5 mm), (b) the transferring and processing of the wafer are performed with a cleanliness level identical to that of a super clean room, and (c) the machine used compact dimensions of 144 cm height, 30 cm width, and 45 cm depth. Since the proposal of the Minimal Fab concept, many Minimal Fab machines and Minimal Fab processes have been developed actively for the fabrication of CMOS integrated circuits [2, 3]. However, the Minimal Fab process for MEMS sensor fabrications has not been developed sufficiently. In this work, we develop the CMOS-MEMS cointegrated process using the Minimal Fab deep-RIE and mask aligner. By using the developed process, we also fabricate and characterize the digital type CMOS-MEMS pressure sensor. The pressure sensing element in the CMOS-MEMS pressure sensor is the CMOS ring oscillator with the longitudinal PMOSFETs located at the edge areas of a thin circular diaphragm. In the device fabrication, we used (100) oriented half-inch SOI wafers, and the source-drain (SD) regions of the MOSFETs were patterned along with the direction to effectively utilize mechanical stress induced drain current variations. As the gate material, we used a 30-nm-thick PVD-TiN layer to obtain a suitable logic gate threshold voltage of the CMOS invertors. The circular diaphragm was fabricated using Minimal Fab mask aligner and deep-RIE. It was confirmed that the oscillation frequency changes from 360 to 400 kHz by changing pressures from -40 to +40 kPa in the fabricated CMOS-MEMS cointegrated pressure sensor chip. The developed CMOS-MEMS pressure sensor is suitable for the application to the battery drive IoT sensor systems owing to its low power consumption. [1] S. Hara et al., J. Jpn. Precis. Eng., vol. 77, no. 3, p. 249, 2011. [2] Y. X. Liu et al., Jpn. J. Appl. Phys. 56, p. 06GG01-1. [3] Y. X. Liu et al., J. Appl. Phys. 57, p. 06HD03-1.

Using a fabrication technology of field emitter arrays (FEAs), we have fabricated a high-density emitter array with 5-10 \mu m pitch as ion sources to improve the thrust density of electrospray thrusters. The emitter array is made on a Si wafer and consists of double Nb electrodes with sub-\mu m apertures, where ionic liquid as the propellant is expected to be extracted by applying voltage to the electrodes. This array can realize the emitter density of up to four million/cm2, which is four orders of magnitude higher than that of conventional electrospray thrusters.

We have proposed and developed a relatively low costed and simple constructed scanning electron microscope only with single objective lens but other convergent electron optics like condenser lenses using graphene-oxide-silicon planar type cold cathode (GOS) as an electron source. GOS has many superior aspects such as low voltage and low vacuum operation, stable emission, high emission current density, high efficiency against diode current, and so on. Especially, the quite low divergence of emitted electron beam from GOS have been expected to realize ideal parallel beam.

A prototype image sensor is developed using cadmium telluride-based photodiode and a volcano-structured FEA. Radiation tolerance of each component was tested by irradiating gamma-ray using cobalt-60 source. Gamma-ray tolerance of up to 1.2 MGy was confirmed for both FEA and photodiode.

Robustness of field emitter arrays (FEA) against high dose rate gamma-ray irradiation was confirmed. The current-voltage characteristics of the FEA were investigated in a vacuum vessel developed for in situ measurements under the irradiation. Although slight increase of the gate current was observed under the irradiation, the insulating layer kept the electrical insulation. As a result, FEA showed the almost identical current-voltage characteristics under the 1.3 kGy h-1 gamma-ray irradiation.

The Minimal Fab system is suitable for low-volume multi-product manufacturing because of its very low initial investment cost. We fabricated volcano-structured Spindt-type field emitter arrays that can be driven in matrix mode for image sensor application by using hybrid process of Minimal Fab system and conventional semiconductor fabrication system. We fabricated 0.6-$\mu \text{m}$-size gated field emitter by using Minimal Maskless lithography system. The planarization using Minimal CMP is performed to prevent break down between matrix type electrode.

The planar type electron emission devices based on a graphene-oxide-semiconductor (GOS) structure were developed. The GOS type electron emission devices fabricated by the combination of low temperature graphene deposition process of 800 $^{\circ\mathrm{C}}$ and the post device annealing at 300 $^{\circ\mathrm{C}}$ in vacuum achieved both of very high electron emission efficiency more than 10 % and high electron emission densities of around 100 mA/cm$^{\mathbf{2}}$

We developed an electron optical instrument for evaluating multi-emitters. This device enables us to evaluate both the percentage of active tips and the stability of the emission current from each active tip. Herein, we employed the instrument to observe a volcano-structured Spindt-type field emitter array (FEA) in the photoelectron emission microscopy (PEEM) and field electron emission microscopy (FEEM) modes. Furthermore, we measured the emission current from each active tip in the FEA. Consequently, we found that the number of active tips in the FEA can be considerably increased by aging at a relatively high voltage.

FDSOI MOSFETs and CMOS ring oscillators with different current flow directions were fabricated on ultrathin circular diaphragms using minimal-fab process, and their electrical characteristics were systematically investigated. It was found that the drain current of the channel MOSFETs and the oscillation frequency of CMOS ring oscillators are changed after diaphragm formation due to residual mechanical stress. This result is very useful for the digital type pressure sensor applications.

Display Omitted The fabrication of the gated nano electron source is overviewed.Breakthrough in the gate formation process enables multi-gated FEA.Spindt-emitter fabrication is now further improved. Many kinds of attractive new applications, such as image sensors, stationary X-ray sources, and the column-less SEM, are investigated as post field emission displays that use a gated nano electron source. The fabrication of the gated nano electron source is overviewed from the conventional method to the latest one, especially in regarding to the gate formation process. Multi-stacked gate electrode formation using an etch-back method was developed recently, which is a very attractive method for generating a focused electron beam. The traditional Spindt-type emitter fabrication method is also being improved to the one that is easier and applicable to large area substrates. Using a double-layered photoresist as a lift-off layer and using HiPIMS sputtering instead of an e-beam evaporator was proposed. Thin film-type FEA fabrication is also improved to make vertically standing thin film by ion irradiation, which is applicable for making an emitter array on a large sized substrate.

Robustness of field emitter arrays against high-energy X-ray irradiation was demonstrated. The current-voltage characteristics of the field emitter array were investigated in a vacuum chamber connected to an electron accelerator. The electron beam with an energy of 1 MeV was incident onto a tungsten thin plate to produce X-rays. The field emitter array showed the almost identical current-voltage characteristics even under the X-ray irradiation, up to the absorbed dose of 1 kGy/h.

To improve the thrust density of electrospray thrusters using ionic liquids as the propellant, we have fabricated a high-density emitter array utilizing the fabrication technique of a field emitter array (FEA) or gated nano electron sources. The density of the emitter array can reach approximately 4 million cm−2, which is four orders of magnitude higher than that of conventional electrospray thrusters. Performing deep reactive ion etching from the back side of the same structure as FEAs and removing their Ni cones by dilute nitric acid, we have successfully fabricated sub-μm scale capillary emitters with self-aligned extractor electrodes and ionic liquid reservoirs behind them. Current measurements were also conducted with EMI-BF4 and EMI-DCA as the propellant. Although the ion was not extracted with EMI-BF4 owing to its electrochemical reaction with the electrodes, both positive and negative ion currents were detected using EMI-DCA, where the current density exceeded that of conventional electrospray thrusters.

The PVD-TiN metal-gate SOI-CMOS integrated circuits including inverters and ring oscillators have successfully been fabricated on a half-inch (100)-oriented SOI wafer using the minimal-fab and mega-fab hybrid process, and their electrical characteristics have systematically been investigated. It was experimentally found that almost an ideal subthreshold slope (SS) of 67 mV/decade and an extremely low leakage current ( t |) for P- and N-channel devices due to the midgap work function of the PVD-TiN are obtained in the fabricated SOI-CMOS devices. Moreover, it was confirmed that the fabricated 41-stage ring oscillators show normal operations at different supply voltages and the oscillation frequencies are close to the estimated values by gate capacitances and drive currents. These excellent results indicate that the developed minimal-fab and mega-fab hybrid process is suitable for the fabrication of conventional CMOS integrated circuits.

A CdTe-based photoconductive target was designed for a radiation tolerant compact image sensor using field emitter array. Gamma-ray irradiation using 60Co showed that this target maintained its photoconductivity even after 1 MGy of gamma-ray irradiation.

Volcano-structured p-type silicon field emitter arrays have been fabricated by etch-back technique and investigated the photoresponse characteristics of electron emission excited by laser pulses. We have observed the current pulses from the device with the same response of the laser pulse.

Radiation tolerance of a field emitter array and a cadmium telluride-based photoconductor was investigated. The variation of the performance of these devices were investigated during the γ-ray irradiation by every 100–200 kGy. Total dose of irradiation reached 1.2 MGy, but no significant deterioration of the properties has been observed. A test tube exhibited successful photo-signal detection even after the irradiation of 1 MGy. As a result, it was found that the field emitter array and the photoconductor have sufficient radiation tolerance against γ-ray irradiation.

Electron emission properties of planar type electron emission device based on graphene-oxide-semiconductor (GOS) structure was investigated. The electron emission efficiency defined as the ratio of anode current to cathode current has no dependence on the graphene electrode thickness, which indicates that the electron scattering within the electrode is perfectly suppressed. A high electron emission current density of 1–100 mA/cm2 with high electron emission efficiency of 0.1–1.0 % was found to be achieved in GOS devices.

We propose a thin-film bending technique based on the ion-induced bending (IIB) phenomenon, which enables the fabrication of three-dimensional structural devices and arrays, such as micro-electro mechanical system (MEMS) devices. We investigated the IIB phenomenon with various film materials and various ion species. It was found that the distribution of vacancy occurs under ion-irradiation was the important parameter affecting the degree of bending, irrespective of film material and ion-species. Therefore, it was found that the bending angle could be controlled by the distribution of vacancy. Using this technique, a micron-sized region of a standing thin-film array could be produced using conventional ion-implantation equipment used in semiconductor manufacturing.

A crossover point was observed with a fabricated quintuple-gated micro-column by an enhanced knife-edge measurement. Developing this result, we designed a new tiny electron beam microscope using multi-gated micro-column by using scale down rule of a micro-column. A beam spot size of the proposed device was estimated to be 50nm by an electron beam trajectories simulation. Exact techniques were developed and demonstrated for the fabrication of the proposed device.

To realize a fine focused electron beam less than several ten nm in diameter, the initial emission angle must be narrowed as much as possible. To control the initial emission angle, we have introduced a suppressor gate below the extractor gate electrode. The paper describes the fabrication of the field emitter array with a built-in suppressor gate.

The electron emission properties of planar-type electron emission devices based on a graphene-oxide-semiconductor (GOS) structure before and after vacuum annealing were investigated. The fluctuation of the electron emission current was around 0.07%, which is excellent stability compared to the conventional field emitter array. The GOS devices were operable in very low vacuum of 10 Pa without any deterioration of their electron emission properties. Improvement of the electron emission properties of the GOS devices was achieved by vacuum annealing at 300 °C. The electron emission efficiency of the GOS type electron emission devices reached 2.7% from 0.2% after vacuum annealing. The work function of the graphene electrode was found to decrease 0.26 eV after vacuum annealing by Kelvin force probe microscopy analysis. These results indicated that the improvement of the electron emission efficiency of the GOS devices by vacuum annealing is due to the decrease in the work function of the graphene electrode.

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.

Volcano-structured double-gate field emitter arrays (VDG-FEAs) were fabricated using the etch-back technique. The fabrication process of the VDG-FEA is simple, and the height (hf) of the focusing electrode relative to the extraction gate electrode is easily adjusted by varying the etch-back time without high-resolution lithography. We have fabricated two types of VDG-FEAs with hf = +220 and 0 nm. The focusing characteristic is controlled by tuning hf. The decrease of the anode current is reduced for the VDG-FEA with lower hf under focusing condition producing the same beam spot size.

We proposed a novel CdTe X-ray image sensor, which was driven by the FEA, to obtain high spatial resolution X-ray images and have demonstrated the principle operation by using the CdTe image sensor with one pixel. We have also fabricated a FEA matrix with 12×12 pixels to obtain X-ray images. For the further improvement of spatial resolution in the CdTe image sensor, we have proposed a novel double-gated FEA with a focusing lens, which was fabricated by using the etch-back method. The double-gated FEA showed a good focusing characteristic without significant decrease of the emission current, when the height of the focus electrode was optimized. The CdTe image sensor driven by the double-gated FEA is promising for an ultra-high-resolution X-ray image sensor.

For superior Au/Al ball-bond reliability, we have developed the 3N (>99.9 wt% Au), 2N5 (>99.5 wt% Au) and 2N (>99 wt% Au) Au alloy bonding wires which contain less than 0.1, 0.5 and 1 wt% Pt, respectively. In the thermal aging test of squashed balls (40 μm in diameter), which consists of storage in air at 250°C and evaluation with wire pull and ball shear, it has been found that there are interesting differences in the ball-bond degradation as a function of wire type. Even the samples bonded using the 3N wire with a very small amount of Pt show superior ball-bond reliability compared with those using a 4N (>99.99 wt% Au) wire without any addition of Pt. The ball-bond degradation in the thermal aging test is reduced significantly with increasing Pt content of a wire. From microstructural analysis of the aged 2N ball bonds, the Pt-containing layer, which seems to play a crucial role in improvement of the ball-bond reliability, have been found in the upper part of intermetallic compounds.

The electrostatic-focusing Spindt-type field emitter array (FEA) pitch was optimized for an FEA-high-gain avalanche rushing amorphous photoconductor (HARP) image sensor. Simulation results showed that a narrow FEA pitch of less than 2.2 µm deteriorates the electrostatic focusing effect.

Volcano-structured double-gate Spindt type field emitter arrays were fabricated using double-layered photoresist as a lift-off layer for the image sensor application. The emitter material that we tested is Ni and Mo/Ni. Electron beam focusing characteristics were evaluated by scanning slit method.

Photoassisted electron emission from p-type silicon field emitter array with sub-micron gate aperture under illumination of blue laser pulses is investigated. The FEA device is designed to minimize the photogeneration of slow electrons outside the depletion layer. We present the optical response studies of the device by laser pulses.

A research project on the development of radiation tolerant compact image sensor with a field emitter array started in 2013. The purpose of the project is to develop key components of the image sensor that has sufficiently high radiation tolerance, as a step to investigate the interior of the nuclear reactor of Nuclear Power Plant Fukushima the 1st. A volcano-structured double-gated Spindt-type field emitter array is now under development. As a photoconductor, a layer of cadmium telluride and cadmium sulfide is adopted. Fundamental characteristics of the image sensor with these components together with the radiation tolerance are examined.

We propose use of silicon field emission array as a novel charge neutralization device for ion implanter. Fundamental characteristics of the emitted electrons, i.e. energy distribution and operation in high vacuum were investigated. As a result, energy spread was narrow enough but unexpected energy peak shift was observed. To reduce the energy spread and peak shift, a FEA with less number of tips and with narrower gate diameter is necessary. The FEA could be operated about 100 h in high vacuum.

We introduce a suppressor electrode into a micro-sized field emitter to control the emission angle, as an alternative to using an aperture. The suppressor electrode is fabricated between the emission tip and the extractor by using an etch-back technique. The suppressor height is determined to be 100 nm below the tip. This structure is expected to control the emission angle to be narrower when applying a low voltage at the suppressor electrode. The emission characteristics of the fabricated device closely follow the behavior of the simulated results. It is shown that the emission angle is narrowed by applying a negative voltage at the suppressor electrode.

Silicon nanowires with programmable conductivity which utilized sensitivity of conductance to surface charging have been investigated in terms of complementary operation of p- and n-type devices. The device fabricated from a silicon-on-insulator (SOI) wafer consists of a nanowire (width ≈ 30 nm) and side gates for control of surface charging onto the nanowire. The wire current clearly exhibited hysteresis by sweeping the side gate voltage at a constant rate. The transistor characteristics obtained using the SOI substrate as a back gate also exhibited programmable threshold voltage by applying a pulse bias to the side gate. Surface potential imaging of the nanowire by means of scanning Maxwell-stress microscopy (SMM) has been carried out for correlating the programmability to surface charging. The SMM images clearly explained the origin of the programmability and the complementary operation of the p- and n-type nanowires.

Vacuum microelectronics is potential technology of building novel electronic devices that cannot be realized by using solid-state electronics. This paper reviews the current status of this technology. Micron-size cold cathodes using field electron emission have been developed for the electron sources of novel vacuum electron devices. Recently field emission displays are getting into the flat panel display market.