EP-4738422-A1 - ELECTRON SOURCE, AND ELECTRON GUN AND DEVICE USING SAME

Abstract

An electron source includes an electron emitting portion containing an alloy of iridium and a rare earth element, a support portion made of a metal, and a joining portion joining the electron emitting portion and the support portion. The joining portion has a coating layer containing iridium and the metal in the support portion, and the coating layer comprises iridium and the metal in the support portion.

Inventors

• HASEGAWA, YOSHITO
• FUJITA, TORU
• TAKEDA, MAMORU

Assignees

• Hamamatsu Photonics K.K.

Dates

Publication Date

20260506

Application Date

20240613

Claims (12)

1. An electron source comprising: an electron emitting portion containing an alloy of iridium and a rare earth element; a support portion made of a metal; and a joining portion joining the electron emitting portion and the support portion, wherein the joining portion has a coating layer covering a surface of the support portion, and wherein the coating layer contains iridium and the metal in the support portion.
2. The electron source according to claim 1, wherein the joining portion further comprises a surrounding portion surrounding at least a part of the coating layer and containing iridium, and wherein, in the surrounding portion, a concentration of a rare earth element is less than or equal to a concentration of the rare earth element in the electron emitting portion.
3. The electron source according to claim 2, wherein the surrounding portion contains the alloy of the iridium and a rare earth element, and a concentration of a rare earth element in the surrounding portion is lower than a concentration of the rare earth element in the electron emitting portion.
4. The electron source according to any one of claims 1 to 3, wherein a coefficient of thermal expansion of the electron emitting portion is greater than a coefficient of thermal expansion of the support portion.
5. The electron source according to any one of claims 1 to 3, wherein the coating layer is a sintered body containing voids.
6. The electron source according to claim 2 or 3, wherein the surrounding portion is a sintered body containing voids.
7. The electron source according to any one of claims 1 to 3, wherein a part of the support portion penetrates the joining portion.
8. The electron source according to any one of claims 1 to 3, wherein the metal in the support portion is composed of at least one selected from the group consisting of tungsten, iridium, molybdenum, tantalum, and rhenium.
9. The electron source according to any one of claims 1 to 3, wherein the rare earth element of the electron emitting portion is composed of at least one selected from the group consisting of cerium, lanthanum, and praseodymium.
10. The electron source according to claim 9, wherein the rare earth element is cerium, and wherein the alloy of the electron emitting portion is composed of at least one selected from the group consisting of Ir 2 Ce, Ir 3 Ce, Ir 5 Ce, and Ir 7 Ce 2 .
11. An electron gun comprising the electron source according to claim 1.
12. A device comprising the electron gun according to claim 11.

Description

Technical Field The present disclosure relates to an electron source, an electron gun and a device using the same. Background Art In devices such as X-ray generators, electron beam generators, electron beam-based metal 3D printers, and electron microscopes (SEM and TEM), an electron gun including an electron source is used. The electron source includes an electron emitting portion and a filament that heats the electron emitting portion. As such an electron source, for example, an electron source described in Non-Patent Literature 1 below is known. The document describes that an IrCe emitter is welded to a tungsten heater filament. Citation List Non Patent Literature [Non-Patent Literature 1] Roberto Rao and Oleg Kultashev, "Ir-Ce cathodes as high-density emitters in electron beam ion sources", 1997, Measurement Science Technology, Volume 8, Number 2, 184 Summary of Invention Technical Problem In an electron source, it is desirable to stabilize the emission amount of an electron beam emitted from an electron emitting portion. For this purpose, it is desired that the temperature of the electron emitting portion is stable during heating. However, the electron source described in Non-Patent Literature 1 has room for improvement in terms of improving the temperature stability of the electron emitting portion during heating. An object of the present disclosure is to provide an electron source capable of improving the temperature stability of an electron emitting portion during heating, an electron gun and an electronic device using the same. Solution to Problem An electron source of the present disclosure provides an electron source including: an electron emitting portion containing an alloy of iridium and a rare earth element; a support portion made of a metal; and a joining portion that joins the electron emitting portion and the support portion, wherein the joining portion has a coating layer that covers a surface of the support portion, and the coating layer contains iridium and the metal in the support portion. According to the electron source, the joining portion has the coating layer covering the surface of the support portion, and the coating layer contains iridium and the metal in the support portion. That is, the coating layer includes both the iridium in the electron emitting portion and the metal in the support portion. For this reason, the coefficient of thermal expansion of the coating layer becomes close to both the coefficient of thermal expansion of the electron emitting portion and the coefficient of thermal expansion of the support portion. Therefore, even when the electron emitting portion is heated by heat generated by energization of the support portion and stress is generated in the joining portion due to a difference in coefficient of thermal expansion between the support portion and the electron emitting portion, the stress is relieved by the coating layer, and the occurrence of cracks in the electron emitting portion is suppressed. As a result, the electron source of the present disclosure can improve the temperature stability of the electron emitting portion during heating. In the electron source, it is preferable that the joining portion further includes a surrounding portion that couples the coating layer and the electron emitting portion and contains iridium, and in the surrounding portion, a concentration of the rare earth element is less than or equal to a concentration of the rare earth element in the electron emitting portion. In this case, since the surrounding portion contains the same iridium as the electron emitting portion and has a concentration of the rare earth element that is less than or equal to the concentration of the rare earth element in the electron emitting portion, a reaction due to heat is less likely to occur between the electron emitting portion and the surrounding portion, and erosion and contamination of the electron emitting portion due to the reaction are suppressed. As a result, the electron source can further improve the temperature stability of the electron emitting portion during heating. In the electron source, it is preferable that the surrounding portion contains an alloy of the iridium and a rare earth element, and a concentration of the rare earth element in the surrounding portion is lower than a concentration of the rare earth element in the electron emitting portion. In this case, the melting point of the surrounding portion becomes lower than the melting point of the electron emitting portion, and the surrounding portion becomes softer than the electron emitting portion. Therefore, even if the support portion expands during heating, the stress due to the expansion is relieved not only by the coating layer but also by the surrounding portion, so that the occurrence of cracks in the electron emitting portion is further suppressed. The electron source is particularly useful when the coefficient of thermal expansion of the electron emitting porti