Kazuto Sakemura

Development of an advanced high efficiency electro-emission device

In this article, we describe the improvement in cold emission characteristics of a device termed HEED (high efficiency electro-emission device) by optimizing the emission site structures. The advanced HEED consists of a bottom electrode, a Si layer, a SiOx layer, a top electrode, and a carbon layer. The electron emission properties were significantly improved by appropriately arranging emission sites of “dimplelike” forms with a diameter of 1 μm on the device surface. The applied voltage was significantly lowered to 20 V (1/5 of that in the previously reported HEED), and a high emission current density of 1.8 mA/cm2 was obtained at a applied voltage of 20 V with an electron emission efficiency of 1% under a pulse operation. The energy distribution measurement of emitted electrons showed that the device emits considerably high-energy electrons as compared with conventional field emitters. Using this emitter as an excitation source, a 4 in. prototype flat display panel has been fabricated with a vacuum spac...

Fabrication of active-matrix high-efficiency electron emission device and its application to high-sensitivity image sensing

Practical advantages of an advanced high-efficiency electron emission device (HEED) (low-voltage operation, relatively simple structure, and availability for large-area applications) are further confirmed by its compatibility with active-matrix drive configuration. The fabricated HEED array has been applied to a high-sensitivity image sensing tube with a target of high-gain avalanche rushing amorphous photoconductor (HARP). It is demonstrated that a prototype 256×192pixel active-matrix HEED array operates well as an effective probe for high-resolution image pickup in combination with a HARP target. The advanced HEED array is promising for development of next-generation image sensor with ultrahigh sensitivity and high definition.

Characterization of an advanced high-efficiency electron emission device

As previously reported, the emission characteristics of metal-insulator-semiconductor (MIS) electron emission devices could be significantly improved by introducing microdimple structures into the emission sites. In this paper, we describe the characteristics of efficient cold electron emitters from a viewpoint of application to flat panel display (FPD). First, the forming operation for the device to activate the dynamic emission is discussed on a basis of the experimental analyses of the electrical properties and output electron energy spectra. Next it is demonstrated that the device has some desirable features as an excitation source of FPD: a high emission current density, a low operation voltage, emission uniformity, and stable emission with small angle dispersion. It is also shown from the result of lifetime evaluation that the device shows a half-life of 3000 h, and that the deteriorated emission can be recovered by the dc reactivation treatment.

Development of a super-high-sensitivity image sensor using 640×480 pixel active-matrix high-efficiency electron emission device

An extremely high-sensitivity image sensor has been developed with a combination of an active-matrix high-efficiency electron emission device (HEED) array and a high-gain avalanche rushing amorphous photoconductor (HARP) target. Following the description of the requirements for the use of the electron emitter as an image-sensing probe, the characteristics of a fabricated 640×480 pixel active-matrix HEED image sensor with a HARP target are presented by image-pickup experiments under a dark condition. The emission current density of the experimental HEED under an active-matrix drive was 4 A/cm2 corresponding to a practical level. A clear image observed in the prototype compact camera demonstrates that the surface-emitting HEED is useful for image sensing based on HARP with high sensitivity and sufficient definition.

2∕3in. ultrahigh-sensitivity image sensor with active-matrix high-efficiency electron emission device

A 640×480pixel image sensor has been developed for low light imaging with a practical resolution. This image sensor combined an active-matrix high-efficiency electron emission device (HEED) with a high-gain avalanche rushing amorphous photoconductor (HARP) target. To meet the requirement for a scaling of the imaging size, we developed a 2∕3in. image sensor based on an active-matrix HEED with 13.75×13.75μm2pixels. The highly emissive property of 3.8μA∕pixel was comparable to that obtained previously from a 1in. device. The possible effect of the pixel size scaling on the image-pickup sensitivity was compensated by a significant increase in the emission current density. The technological potential of the HEED-HARP image sensing has been further enhanced toward practical use.

Enhanced output current density of an active-matrix high-efficiency electron emission device array with 13.75μmpixels

An active-matrix array of high-efficiency electron emission device (HEED) with a sufficient output density has been developed for the use as imaging probe in a high-gain avalanche rushing amorphous photoconductor target. Previously, it was demonstrated that a prototyped image sensor with 20×20μm2pixels could pick up a high definition image with an ultrahigh sensitivity under low-light-level condition. Based on it, an efficient active-matrix HEED with 13.75×13.75μm2pixels is fabricated for pursuing higher sensitivity and resolution. The improvement in the device isolation method enables to enlarge the relative emitting area, and then the emission current density per pixel reaches 3.6A∕cm2 that is about four times of that obtained from the previous one. The active-matrix HEED array with small pixels is available for application to the compact ultrahigh-sensitivity image sensor without affecting on the image definition.An active-matrix array of high-efficiency electron emission device (HEED) with a sufficient output density has been developed for the use as imaging probe in a high-gain avalanche rushing amorphous photoconductor target. Previously, it was demonstrated that a prototyped image sensor with 20×20μm2pixels could pick up a high definition image with an ultrahigh sensitivity under low-light-level condition. Based on it, an efficient active-matrix HEED with 13.75×13.75μm2pixels is fabricated for pursuing higher sensitivity and resolution. The improvement in the device isolation method enables to enlarge the relative emitting area, and then the emission current density per pixel reaches 3.6A∕cm2 that is about four times of that obtained from the previous one. The active-matrix HEED array with small pixels is available for application to the compact ultrahigh-sensitivity image sensor without affecting on the image definition.

Development of a high-resolution active-matrix electron emitter array for application to high-sensitivity image sensing

An active-matrix planar-type cold electron emitter array for application to high-sensitivity image sensors have been developed. A 640times480 pixel active-matrix HEED (high-efficiency electron emission device) with 20times20 mum pixels was fabricated, and the emission current density of 1 A/cm2 has been obtained at an applied voltage of 23 V. Further studies toward the next generation image sensor with a high sensitivity are in progress

2/3-inch ultra-high-sensitivity image sensor with active-matrix high-efficiency electron emission device

A flat type image sensor consisting of a field emitter array (FEA) and a high-gain avalanche rushing amorphous photoconductor (HARP)[1] target is developed as the low light imaging compact camera for broadcasting, industry, biology, and so on [2]. In the previous IVNCs, we reported the development of a 1-inch image sensor which consisted of a high-efficiency electron emission device (HEED) [3] with 20 × 20 μm2 pixels [4]. The experiment on the image sensor confirmed an extremely high sensitivity under low-light illumination with a sufficient resolution as expected from the emitter pixel size. For scaling the pixel size further, we developed an active-matrix HEED array with 13.75 × 13.75 μm2 pixels [5]. Fig. 1(a) shows a top-view SEM image of the active-matrix HEED with 13.75 × 13.75 μm2 pixels. For comparison, the image of the previous device is also shown in Fig. 1(b). The improvement in the device isolation method enabled to enlarge the relative emitting area, and then the emission current density per pixel reached 3.6 A/cm2. This highly emissive property fulfilled the imaging requirement of a FEA-HARP image sensor. The device had 640 horizontal and 480 vertical pixels, and the imaging area was 8.8 × 6.6 mm2. The size of this imaging area corresponds to the optical system for the 2/3-inch. The specifications of the active-matrix HEED with 13.75 × 13.75 μm2 pixels, and that of previous one are summarized in Table 1. In this paper, we describe the structure and fundamental characteristics of a prototype 2/3-inch HEED-HARP image sensor.

640×480 pixel active-matrix HEED imaging sensor with HARP target

In this paper, an active-matrix planar-type cold electron emitter array development is studied to fulfill the requirement of high-speed response. This emitter array adopts a novel MIS emitter which is termed HEED (High-efficiency Electron Emission Device) and fabricated on a MOS transistor array formed on a silicon wafer with scan driver circuits. HEEDs driving voltage is relatively low (about 20V) and its MIS structure is compatible with silicon planar processing employed for LSI. As a consequence, The HEED is one of the most suitable emitters for an active-matrix drive configuration. The emission current density (defined as the average pixel current per emitter area size) reaches up to 4.4 A/cm . This highly emissive property fulfills the imaging requirement of a HARP target. The specifications of the active-matrix HEED are summarized. The number of the interconnections to drive this chip is applicatory 12 lines. This is another important advantage of the active-matrix drive method.

Development of a High-Resolution Active-matrix Electron Emitter Array for Application to High-Sensitivity Image Sensing

An active-matrix planar-type cold electron emitter array for application to high-sensitivity image sensors have been developed. A 640times480 pixel active-matrix HEED (high-efficiency electron emission device) with 20times20 mum pixels was fabricated, and the emission current density of 1 A/cm2 has been obtained at an applied voltage of 23 V. Further studies toward the next generation image sensor with a high sensitivity are in progress