Manufacturing method of electron source

Abstract

An electron gun with a truncated-cone-shaped cathode with uniform emission current density is efficiently manufactured. A manufacturing method of a cathode electron gun equipped with a supply source for diffusing oxide of a metal element on a single crystal needle of tungsten or molybdenum includes steps of forming a truncated-cone-shape having a flat plane at a single crystal edge serving as the cathode by machining beforehand, thereafter thinning and removing a front layer of the flat plane by a focused gallium ion beam, and re-flattening it.

1 . A method of manufacturing an electron source having an electron emission portion at one tip portion of a rod, the method of manufacturing an electron source comprising a step of forming the tip portion in the shape of a truncated cone having a flattened surface by a machining process, and a step of removing a surface layer of the flattened surface by focused ion beam processing or vapor phase etching. 
     
     
         2 . The method of manufacturing an electron source according to  claim 1 , further comprising, between the step of forming in the shape of a truncated cone and the step of removing a surface layer of the flattened surface by focused ion beam processing, a step of removing a processing scar layer on the surface of said tip portion by means of vapor phase etching or electrolytic polishing. 
     
     
         3 . The method of manufacturing an electron source according to  claim 1 , wherein said step of removing a surface layer of the flattened surface is a step of removing the surface layer of the flattened surface by irradiating with a focused gallium ion beam in an atmosphere of xenon difluoride gas. 
     
     
         4 . The method of manufacturing an electron source according to  claim 1 , wherein said step of removing a surface layer of the flattened surface is a step of removing the processing scar layer of the surface layer of said tip portion including the surface layer of said flattened surface by performing vapor phase etching under conditions of an oxygen pressure of at least 0.3×10 −4  Pa and at most 8×10 −4  Pa, and a temperature of at least 1700 K and at most 1950 K. 
     
     
         5 . The method of manufacturing an electron source according to  claim 1 , wherein the diameter of said flattened surface is at least 10 μm and at most 100 μm. 
     
     
         6 . The method of manufacturing an electron source according to  claim 1 , wherein said electron source is an electron source obtained by providing a reservoir for diffusion of oxides of metal element to a monocrystalline rod of tungsten or molybdenum in the <100>orientation. 
     
     
         7 . The method of manufacturing an electron source according to  claim 6 , wherein said metal element is chosen from among Ca, Sr, Ba, Sc, Y, La, Ti, Zr, Hf and the lanthanoids.