High-efficiency Electron Emission Device Research Articles

2 ∕ 3 in. 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.

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.

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

An image sensor consisting of an active-matrix high-efficiency electron emission device (HEED) array and a high-gain avalanche rushing amorphous photoconductor (HARP) has been fabricated. Based on the demonstration that a prototyped 256×192pixel image sensor can pick up a high definition image with an ultrahigh sensitivity under poor light condition, the authors have been developing a 640×480pixel active-matrix HEED toward a practical use. The emission current density has been enhanced more than twice compared to that of previous one and has increased up to 1A∕cm2. The active-matrix HEED array combined with HARP is available for application to practical image sensing with an ultrahigh sensitivity and high definition.

１インチ２５６×１９２画素アクティブ駆動型ＨＥＥＤ冷陰極ＨＡＲＰ撮像板

We made an active-matrix high-efficiency electron emission device (HEED) that had scanning driver circuits fabricated with conventional MOS planer technology.A 1-in 256x192 pixel image sensor,consisting of the active-matrix HEED and a high-gain avalanche rushing amorphous photoconductor (HARP) target,was fabricated and tested as a step toward the development of ultrahigh-sensitivity compact image sensors with a large number of pixels.The experimental results show that the prototype sensor can be used to obtain clear images even under dark lighting conditions,such as in moonlight,and that the active-matrix HEED is a promising highspeed image pick-up device.

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.