Lanthanum hexaboride (LaB{sub}6) is a material with low work function, low resistivity, low sputtering yield, high melting point and high chemical stability. It has been widely used as thermionic emitters. On the other hand, LaB{sub}6 is also an excellent material for use as field emission cathodes. In this paper, field emission cathode single tip was fabricated by electro-chemical etching method. The materials used here were single crystal lanthanum hexaboride (LaB{sub}6), polycrystalline lanthanum hexaboride, molybdenum, and tungsten, respectively. Fig.1 and fig.2 were the SEM pictures about single crystal LaB{sub}6 and molybdenum. Electron emission characteristics of single crystal LaB{sub}6 cold cathode were studied in a diode test cell in vacuum system. When the distance between the single crystal LaB{sub}6 tip and the anode was 0.2mm, current density of 1.25×10{sup}4A/cm{sup}2 was obtained at a pressure of 3.4×10{sup}(-4)Pa with DC-3000V bias applied to the anode. Decreasing the vacuum condition to 1×10{sup}(-3)Pa and changing the anode voltage, we compared the current density of single crystal LaB{sub}6 with other material cathodes, which showed that the current density of single crystal LaB{sub}6 was much higher than other material cathodes (fig.3).
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