US-12617713-B2 - Substrate, method for producing substrate, and method for producing unit cell

Abstract

The problem of the present invention is to provide a substrate with high versatility, a method for producing the substrate, and a method for producing a unit cell using the substrate. The problem is solved by providing a substrate comprising a plurality of alkali metal azide spots on a substantially flat surface.

Inventors

• Motoaki Hara
• Yuichiro YANO
• Tetsuya Ido
• Hikaru Tanaka
• Kazutake Hagiya
• Yasuhiro Sato

Assignees

• NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATIONS TECHNOLOGY
• TOYOBO MC CORPORATION

Dates

Publication Date

20260505

Application Date

20220127

Priority Date

20210311

Claims (14)

1. 1 . A substrate comprising a plurality of alkali metal azide spots on a substantially flat surface, wherein the substantially flat surface is a surface having no partition walls and optionally including recesses having a depth of 20% or less of a thickness of the substrate.
2. 2 . The substrate according to claim 1 , wherein the substrate comprises a plurality of the recesses scattered in a spot-like pattern on the substantially flat surface, and each of the alkali metal azide spots is formed in each of the recesses.
3. 3 . A method for producing the substrate according to claim 1 , wherein a coating formed from an alkali metal azide-containing liquid is formed in a spot shape on a substrate member.
4. 4 . The method according to claim 3 , wherein a mask having holes scattered in a spot-like pattern is formed on the substrate member, the alkali metal azide-containing liquid is applied on the mask to form the coating, and then the mask is removed.
5. 5 . The method according to claim 3 , wherein the alkali metal azide-containing liquid is applied to the substrate member to form the coating, and then the coating is partially removed to leave the alkali metal azide in a spot-like pattern on the substantially flat surface.
6. 6 . A method for producing the substrate according to claim 2 , wherein an alkali metal azide-containing liquid is applied to a substrate member so as to remain only in the recesses to form a coating formed from the alkali metal azide-containing liquid in a spot shape in each of the recesses.
7. 7 . The substrate according to claim 1 , wherein the thickness of the substrate is from 100 μm to 1.0 mm.
8. 8 . The substrate according to claim 1 , wherein each alkali metal azide spot is a spot composed only of an alkali metal azide.
9. 9 . The substrate according to claim 1 , wherein a circle-equivalent diameter of each alkali metal azide spot is from 50 μm to 2.0 mm.
10. 10 . The substrate according to claim 1 , wherein the plurality of alkali metal azide spots have the same shape and size.
11. 11 . The substrate according to claim 2 , wherein an outer diameter of each recess, in terms of circle-equivalent diameter, is from 50 μm to 2.0 mm.
12. 12 . The substrate according to claim 2 , wherein the depth of each recess is from 1 μm to 200 μm.
13. 13 . The substrate according to claim 2 , wherein the plurality of recesses have the same shape and size.
14. 14 . A unit cell formed from the substrate according to claim 1 .

Description

TECHNICAL FIELD The present invention relates to a substrate, a method for producing the substrate, and a method for producing a unit cell using the substrate. BACKGROUND ART A cell in which an atomic gas is sealed (hereinafter also referred to as a gas cell) is used in an atomic device such as a high-precision atomic clock based on the frequency of an electromagnetic wave absorbed by the atom, an atomic magnetic sensor which uses optical pumping of the atom, or the like. As a production method of such a gas cell, a method is known in which a cell container is produced by glass fusion bonding or blowing, an alkali metal gas and a buffer gas are blown into the container, and the gases are sealed by pinching off (Non-Patent Documents 1 and 2). However, the production methods disclosed in Non-Patent Documents 1 and 2 involve complicated operations, have difficulty in miniaturizing a cell, and are not suitable also for mass production. From the viewpoint of miniaturization of a cell and cost reduction through mass production, a method for producing a cell by a wafer process has been studied (Non-Patent Documents 3 and 4). RELATED ART DOCUMENTS Non-Patent Documents Non-Patent Document 1: J. Gouloumet, B. Leuenberger, C. Schori, S. Grop, and R. Rochat, “Progress towards a compact and low-power miniaturized Rubidium Oscillator (mRO™)” IEEE/MTT-S International Microwave Symposium, 2020, p. 876-879Non-Patent Document 2: H. Zhang, H. Herdian, A. T. Narayanan, A. Shirane, M. Suzuki, K. Harasaka, K. Adachi, S. Goka, S. Yanagimachi, and K. Okada, “ULPAC: A Miniatured Ultralow-power Atomic Clock” IEEE Journal Of Solid-State Circuits, 2019, 54(11), p. 3135-3148Non-Patent Document 3: S. Karlen, J. Gobet, T. Overstolz, J. Haesler, and S. Lecomte, “Lifetime assessment of RbN3-filled MEMS atomic vapor cells with Al2O3 coating” Optics express, 2017, 25(3), p. 2187-2194Non-Patent Document 4: L. Liew, J. Moreland, and V. Gerginov, “Wafer-level filling of microfabricated atomic vapor cells based on thin-film deposition and photolysis of cesium azide” Applied Physics Letters, 2007, 90(11), 114106 SUMMARY OF THE INVENTION Problems to be Solved by the Invention In the production method of a gas cell disclosed in Non-Patent Document 3, RbN3 aqueous solution is pipetted into the cavities of a substrate where partition walls are formed to separate multiple cells, followed by drying, and the cavities are then hermetically sealed by anodic bonding of glass to the openings. The size and shape of a gas cell are required to be designed according to an atomic device to be used, whereas, in the production method of a gas cell disclosed in Non-Patent Document 3, the cell shape cannot be changed after dispensing the RbN3 aqueous solution to the cells, and thus such a gas cell has less versatility. In the production method of a gas cell disclosed in Non-Patent Document 4, a CsN3 film is formed by vapor-phase film formation by vapor deposition in the cavities of a substrate where partition walls are formed to separate multiple cells, and the cavities are then hermetically sealed by anodic bonding of glass to the openings. However, even in the production method disclosed in Non-Patent Document 4, the cell shape cannot be changed after dispensing CsN3 to the cells, and thus such a gas cell has less versatility. In addition, in the above vapor deposition, explosion and bumping of CsN3 are likely to occur during heating, and the CsN3 film formed may be non-uniform. Thus, the enclosed amount of Cs was not quantitative, and uniform unit cells could not be obtained. The present invention has been made by focusing on the above situation, and an object of the present invention is to provide a substrate with high versatility, a method for producing the substrate, and a method for producing a unit cell using the substrate. Solutions to the Problems The gist of the present invention is as follows. [1] A substrate comprising a plurality of alkali metal azide spots on a substantially flat surface.[2] The substrate according to [1], wherein the substrate comprises a plurality of recesses scattered in a spot-like pattern on the substantially flat surface, and each of the alkali metal azide spots is formed in each of the recesses.[3] A method for producing the substrate according to [1] or [2], wherein a coating formed from an alkali metal azide-containing liquid is formed in a spot shape on a substrate member.[4] The method according to [3], wherein a mask having holes scattered in a spot-like pattern is formed on the substrate member, the alkali metal azide-containing liquid is applied on the mask to form the coating, and then the mask is removed.[5] The method according to [3], wherein the alkali metal azide-containing liquid is applied to the substrate member to form the coating, and then the coating is partially removed to leave the alkali metal azide in a spot-like pattern on the substantially flat surface.[6] A method for producing the substrate according