Hidetaka Shimawaki

Resonant Fowler–Nordheim tunneling emission from metal-oxide-semiconductor cathodes

A metal-oxide-semiconductor tunneling cathode was fabricated with an ultrathin oxide layer and an abrupt interface between the oxide layer and the polycrystalline Si gate electrode. The emission current shows periodic deviations on the Fowler–Nordheim plot estimated by the Wentzel–Kramers–Brillouin (WKB) approximation. The peaks in the oscillations are confirmed to arise from the resonant effect of electron tunneling by comparing the experimental results with the theoretical calculations. This article describes the first experiment of resonant tunneling emission.

Photoresponse of a p-type Si field emitter

The high-frequency bunched-beam (pulsed beam train) generated directly from a cathode is strongly desired for a compact microwave vacuum tube with high efficiency. The emission current from a p-type semiconductor field emitter saturates in dark with increase of the gate voltage because of the supply limit of the minority carrier. When a p-type emitter is illuminated by light with photon energy larger than the band gap energy, the emission current is remarkably increased because of the additional supply of the photo-excited carriers. It suggests that the bunched beam could be obtained, when the p-type emitter is irradiated with a pulsed laser beam. The frequency of the bunched beam, however, is limited by the photo-response of the emitter. Therefore, we investigated the photo-response of a p-type Si field emitter under the irradiation of a pulsed laser beam.

Improvement of the emission current from a cesiated metal-oxide-semiconductor cathode

We have reduced the work function of the gate electrode of a metal-oxide-semiconductor tunneling cathode by cesiation. After cesiation, there was a considerable increase in the emission current and a large number of electrons were detected at energies lower than the original vacuum level of the poly-Si gate electrode. These results indicate that almost all the tunneling electrons have energies lower than the original vacuum level of the gate electrode, and that after cesiation electrons initially prevented from being emitted by the original vacuum level were emitted, because of the reduced work function due to cesiation.

A monolithic field emitter array with a JFET

This paper proposes a novel structure of the conical Si field emitters monolithically incorporating a vertical-type junction field effect transistor (JFET) and demonstrates the emission control in field emission from the emitters. The proposal has many attractive advantages in the display application and reliable fabrication, because the structure needs neither additional area for the JFET nor additional process except ion implantation. The experimental results of the emitters show excellent controllability and stability in the emission current.

Smith-Purcell radiation from ultraviolet to infrared using a Si field emitter

Smith-purcell radiation using a Si-field emitter has been generated and detected in both ultraviolet and infrared regions. We passed a 200 nA beam current accelerated in 25-30 kV over a 550 nm pitch grating and detected the 1st harmonic waves of SPR in the infrared region from 1300 to 1400 nm by using an InGaAs detector. In addition to them, the 4th harmonic waves of SPR in the ultraviolet region from 320 to 360 nm were clearly observed by using a CCD detector. These spectra also coincided with those of the calculation using the SPR theory and blue-shifted with increasing the acceleration voltage. As results, we have successfully observed SPR from ultraviolet to infrared using a Si field emitter for the first time.

Smith–Purcell radiation using a single-tip field emitter

Smith-Purcell radiation (SPR) was generated from a single-tip Si field emitter at a low power level. Single-tip Si field emitters were fabricated using reactive ion etching and thermal oxidation sharpening. Radiation measurements were performed through a viewing port in the visible spectra. SPR was successfully observed at 300-900 nm wavelength, 20-200 nA beam current and 25-30 kV accelerating voltage.

Electron emission from planar-type cathodes based on nanocrystalline silicon thin films

Many types of cold cathodes have been studied to realize a high and stable electron emission current. Emission uniformity over a large cathode area and small energy dispersion in emitted electrons are essentially important for a field emission display and high frequency electron beam devices. In addition, a low cost and reliable fabrication of the cathode is also important. We have fabricated nanocrystalline Si planar cathodes by a laser ablation technique and investigated their emission characteristics.

Energy distributions of field emission electrons from silicon emitters

The energy distributions of field-emitted electrons from single-tip n type and p type Si field emitters have been analyzed. The energy distributions of both n type and p type Si emitters show a single peak, and the peak position shifts slightly towards the low energy side in the n type emitter as the gate voltage is increased. In the case of the p type emitter a considerably larger shift towards lower energies is observed. The distributions from the n type emitter have the same threshold energies near the Fermi level energy and become broader with the increase in the gate voltage. On the other hand, the threshold energies of the p type emitter are more than 1.5eV below the Fermi level and shift to the lower energy side as well as the peak position in the energy distribution with increasing the gate voltage. In addition, the energy distributions of the p type emitter are considerably broad in comparison with those of the n type emitter, but the full width half maximums (FWHMs) of the distributions do not s...

Emission characteristics of a GaAs wedge emitter monolithically fabricated with an air bridge and a cantilever anode

GaAs wedge emitters with an air bridge anode and a cantilever anode were monolithically fabricated using a micromachining technique. The threshold voltage of electron emission is about 8 V for the diode between the emitter and the air bridge anode, while only 1.5 V for the diode between the emitter and the cantilever anode. The current–voltage characteristic of the air bridge diode is due to a field emission, on the other hand, that of the cantilever diode is recognized as a direct tunneling of electrons through the reduced air gap between the emitter and the cantilever by electrostatic force.

P1–24: Photo-assisted electron emission from MOS-type cathode based on nanocrystalline silicon

Enhancement of electron emission by illumination of a metal-oxide-semiconductor (MOS)-type cathode based on nanocrystalline silicon has been studied using a He-Ne laser. Heavily doped p-type silicon was used as a substrate and the laser was irradiated on the gate with oblique incidence. The emission current was enhanced under illumination and quickly responded to on-off of the laser. In addition, the threshold voltage for the electron emission decreased.