A metal-oxide-semiconductor (MOS) tunneling cathode is a fine electron source for vacuum nanoelectronic devices and many other electron beam devices, because the cathode operates at low extraction voltage, has pressure insensitivity of emission current, and uniform and highly directional emission from the whole emitting area. However, the device is not practically used yet because of the low emission efficiency of about ～1%. On the other hand, for the modified MOS cathode whose oxide layer was replaced with semi-insulating films such as non-doped Si or nanocrystalline Si, the high emission efficiencies over than 10% have been reported [1-3]. Although the mechanism of such a high efficiency is not still understood, the use of nanocrystalline structures is a promising way to improve the performance of the MOS cathode. We have fabricated nanocrystalline Si MOS cathodes by a laser ablation technique as the first step to understand the emission mechanism of nanocrystalline-based cathodes because the technique is appropriate for fabricating nanocrystalline Si covered with a thin oxide layer, and investigated their emission characteristics.
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