• Applied Microscopy
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• v.46 no.1
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• pp.20-26
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• 2016

Our work on $Sc_2O_3-W$ matrix dispenser cathodes had been reviewed in this paper. The cathode with uniform distribution of $Sc_2O_3$ had been obtained using liquid-liquid doping method. The cathode had excellent emission property, i.e., the emission current density in pulse condition could reach over $35A/cm^2$. It was found that the cathode surface was covered by a Ba-Sc-O active substance multilayer with a thickness of about 100 nm, which was different from the monolayer and semiconducting layer in thickness. Furthermore, the observation results displayed that nanoparticles appeared at the growth steps and the surface of tungsten grains of the fully activated cathode. The calculation result indicated that the nanoparticles could cause the increase of local electric field strengths. We proposed the emission model that both the Ba-Sc-O multilayer and the nanoparticles distributing mainly on the growth steps of the W grains contributed to the emission. The future work on this cathode has been discussed.