Study of Field Emission Cathode by Field Ion Microscopy

概要

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A blunting and build-up phenomena for field emission cathode of tungsten tip have been observed with the field ion microscope operated by hydrogen gas. The change of the radius on each crystal plane of tungsten tip during the heat treatment is estimated from the voltage applied to obtain the fine field ion image. The diffusion constant of migration of tungsten atoms in blunting process is represented by D=D_0exp(-Q/KT) and the diffusion energy Q:2.3eV and diffusivity constant D_0:3.6×10^<-3>cm^2/sec are obtained from the change of radius of tip for various temperature. Several kinds of build-up form are obtained by different electric field strength and temperature. The build-up surface of tip is easily reformed by heat-treatment and the rate of reformation coincides with the theoretical value estimated from Herring's theory on the simple model, using the diffusion constant obtained from our experimental value of blunting rate. The recrystallization by heat-treatment on tungsten tip torn off by high electric field and on the tip with the polyhedral shape etched electrolytically are observed. The apex of the hemi-spherical surface of tungsten tip always coincides with (011) plane after heat-treatment.
社団法人応用物理学会の論文
1962-07-15