The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 09, 1998
Filed:
Mar. 04, 1996
Hidetoshi Nisiyama, Kodaira, JP;
Masakuni Okamoto, Kokubunji, JP;
Hiroyuki Shinada, Chofu, JP;
Katsuhiro Kuroda, Hachioji, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A cathode (e.g., a Schottky emission cathode) having an electron emitter of a tungsten single-crystal with a sharp point, and a heater connected to the electron emitter to heat it. The work function of the crystal face of the point of the electron emitter is reduced by providing adsorbed thereon a nitride of Zr, Ti, Y, Nb, Sc, V or La, or an oxide of Y, Sc, V or La. The nitride or oxide can be formed as a reservoir on the heater (from where it thermally diffuses to the point), or chemically adsorbed on the point. For forming the nitride or oxide on the point, the metal forming the nitride or oxide can be provided on the point and reacted with nitrogen or oxygen thereat to form the nitride or oxide; to provide the metal on the point, the metal forming the nitride or oxide can either be evaporated onto the point, or can form a reservoir on the heater and thermally diffuse therefrom to the point. The effect of reducing the work function results in a cathode having a narrow FWHM (full width at half maximum) of emission electrons and a high current density.