Study On Preparation Of Lanthanum Hexaboride Field Emission Cathode Arrays

In contrast with conventional thermo-ionic cathode, field emitter array (FEA) cathode has many special advantages, such as room-temperature operation, high current density, low power dissipation, excellent ON/OFF isolation characteristics and instant turn-on characteristics. At present, FEAs have potential for use as an electron source in a wide variety of applications, including microwave power amplifiers, flat panel displays, electron microscopy, and electron beam lithography. The research focus concentrates on the use of FEAs as a cold cathode source for microwave power amplifiers or flat panel displays.When we produce field emitting cold cathodes, we must consider not only the work function, conductance, density, reliability and mission capability but also the demand of technique. At present, lots of materials and preparation methods of field emitting cold cathodes are being developed. But the materials of emitting cathode are mostly present with big escaping power,low reliability,low uniformity and emission capability. However, as one kind of the better materials, LaB₆ is so perfect with it's excellent physical and chemical characteristics,low work function,high conductance and activity surface. According to the literature in the world, now the research of LaB₆ is not mostly concentrates on field emission sphere but hot emission.In this paper, a series of LaB₆ field emitting cathode arrays have been fabricated with the methods of electrochemistry eroding, oxidation and evaporation etching, and plasma etching separately. We have researched each process and analyzed some factors which influence the consequence. From the results, we can see that the impact of isotropy should not be neglected in electrochemistry eroding, so we must confirm accurately the crystal orientation before using this method. Using oxidation and evaporation etching, we have to consider the properties of protecting films, including film's thickness, compactness, properties in high temperature, and the adhesion between films and the base. The problems of protecting films also should be considered in plasma etching, because most of films slough easily from the base when bombarded by ion. In this paper, LaB₆ field emitting cathode arrays have been fabricated successfully with oxygenic plasma etching, in which SiO₂-SiN_x composite was selected as protecting film. The results demonstrate the etched surface finish quality and flat quality are excellent, the cone's shape and bulk are uniform and the height of the cone approximates 2.3 micron.