A vacuum has several advantages over a solid as an electron transport medium. However, conventional vacuum devices have several disadvantages such as large size and high power consumption because thermal cathodes are used. Recent micro- or nano-fabrication technology enables the development of functional field emitter arrays such as field emitters monolithically incorporating a vertical-type field effect transistor and field emitters with an electro-static lens. In this paper I introduce these functional field emitter arrays and the vacuum nanoelectronics devices which are being developed. I describe the expectation to vacuum nanoelectronics which provide compact, stable at harsh conditions, and high frequency/power output.

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 Field emitter arrays (FEAs) have been investigated as potential cold cathodes in variety of applications such as flat-panel displays and image sensors, microwave and further high frequency vacuum electronic devices. The density modulated electron beam (a train of electron bunches) at high frequency generated directly from the cathodes offers opportunities for dramatic improvements in performance of microwave vacuum electronic devices. The paper discusses the emission characteristics and optical response of gated p-type silicon field emitter arrays under irradiation of laser pulses.

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 Field emission features from Si and W tips are drastically improved upon coating even with simple carbon films. In this paper, in order to obtain clues to clarify the mechanism, we examine atomistic STM observations including local barrier height (LBH) and field emission imagings of the carbon films. And we also examine the field emission features from the shape-controlled W tips before and after the carbon coatings, enabling us to estimate the local electric field at the tip apex. From the STM observations, we find that the carbon film consists of nm-scale grains with various electronic properties and that the FE current varies grain by grain and is higher near the edge of each grain. The effective work functions evaluated from the slopes of the Fowler-Nordheim (FN) plot are constant regardless of the thickness of the carbon coating, although they are largely scattered for the films thinner than 1 nm. On the basis of the observed results, we discuss the mechanism of low macroscopic field emission from carbon films.

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 A 640×480 pixel field emitter array (FEA) image sensor with 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 for high-definition TV cameras. Experiments showed that the prototype sensor could obtain clear images with little noise under illumination on a level equivalent to moonlight, with sufficient resolution while consuming far less power than current ultrahigh-sensitivity pickup tubes. Furthermore, various technologies which were suitable for practical image sensor have been developed.

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