Method for manufacturing a defect-free large-scale single-crystalline metal foil

Abstract

A method for manufacturing a single-crystalline metal foil, particularly a method for manufacturing a large-scale single-crystalline metal foil, to address the issues of poor quality and insufficient stability in the single-crystalline growth process associated with conventional manufacturing methods. The method includes: placing a metal foil to be processed on a holder such that at least a portion of the metal foil is suspended due to gravity, and placing the metal foil together with the holder in a chamber; adjusting the pressure inside the chamber to a predetermined pressure; introducing an inert gas into the chamber and heating the chamber to a predetermined temperature; at the predetermined temperature, introducing both the inert gas and hydrogen gas into the chamber and maintaining the process for a predetermined period; and introducing the inert gas into the chamber while allowing the chamber to cool naturally. By this method, the quality of the single-crystalline metal foil and the stability of the single-crystalline growth process can be improved.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a single-crystal metal foil, and more particularly to a method for preparing a single-crystal metal foil by means of annealing treatment. [Previous Technology]

[0002] Single-crystal metal foils are widely used as growth substrates for two-dimensional materials such as graphene, and the crystal quality of the single-crystal metal foil has a significant impact on the quality of the final two-dimensional material. Currently available single-crystal metal foils are mainly manufactured through bulk polycrystalline growth or epitaxial growth on substrates. However, these methods are difficult to achieve large-area, highly uniform single-crystal metal foils, and the manufacturing process is relatively complex.

[0003] In addition, there is a method for preparing single-crystal metal foil from polycrystalline metal foil using high-temperature annealing. However, this annealing method typically involves placing the polycrystalline metal foil horizontally in a heating chamber. The contact between the metal foil and the chamber leads to uneven thermal expansion, which hinders single-crystal grain growth, increases surface roughness, and consequently results in poor quality single-crystal metal foil. Furthermore, in this method, the control of the gas environment is crucial for the formation of the single-crystal structure, but the control of gas composition and flow rate has not yet been optimized, leading to insufficient stability during the single-crystal growth process.

[0004] In view of this, there is indeed a need to improve the conventional methods for manufacturing single-crystal metal foils. [Summary of the Invention]

[0005] To solve the above problems, the purpose of this invention is to provide a method for manufacturing single-crystal metal foil, which can produce single-crystal metal foil of good quality.

[0006] A second object of the present invention is to provide a method for manufacturing a single crystal metal foil, which can improve the stability of the single crystal growth process.

[0007] Another object of the present invention is to provide a method for manufacturing single crystal metal foil, which can manufacture large-area single crystal metal foil.

[0008] The directions or similar terms used throughout this invention, such as "front", "back", "left", "right", "top", "bottom", "inner", "outer", "side", etc., are mainly for reference to the directions in the accompanying drawings. Each direction or similar term is only used to help explain and understand the various embodiments of this invention and is not intended to limit this invention.

[0009] The use of the quantifiers “a” or “an” for the elements and components described throughout this invention is for convenience and to provide the general meaning of the scope of the invention; in this invention, it should be interpreted as including one or at least one, and a single concept also includes plural cases, unless it clearly means otherwise.

[0010] The terms "first", "second", ... and "Nth" used throughout this invention are mainly used to distinguish different elements or features (such as elements, directions or steps, etc.) and do not indicate the maximum or minimum number of such elements or features possessed by a corresponding subject or method, nor do they limit the order of priority.

[0011] The method for manufacturing a single-crystal metal foil of the present invention includes: placing a metal foil to be processed on a support, such that at least a portion of the metal foil to be processed is suspended due to gravity, and placing the metal foil to be processed together with the support in a chamber; bringing the pressure in the chamber to a predetermined pressure; introducing an inert gas into the chamber at a first inert gas flow rate, and bringing the ambient temperature in the chamber to a predetermined temperature; at the predetermined temperature, introducing the inert gas into the chamber at a second inert gas flow rate, and simultaneously introducing hydrogen into the chamber at a hydrogen flow rate, and maintaining this at a predetermined time; and introducing the inert gas into the chamber at a third inert gas flow rate, and allowing the chamber to cool naturally; wherein the first inert gas flow rate is 1~500 sccm, the predetermined temperature is 1000~1500°C, the second inert gas flow rate is 200~500 sccm, and the hydrogen flow rate is 1~200 sccm. The scheduled time is 8 to 22 hours, and the third inert gas flow rate is 1 to 500 sccm.

[0012] Accordingly, the method for manufacturing single-crystal metal foil of the present invention, by employing the support structure that makes the metal foil to be treated hang, can promote single crystal growth by utilizing the weak gravity effect during the annealing process, which is beneficial for manufacturing large-area single-crystal metal foil on an industrial scale, and can effectively reduce the adverse effects caused by the contact between the metal foil to be treated and the chamber, thereby improving the quality of the obtained single-crystal metal foil; and by controlling the flow rate and ratio of inert gas and hydrogen, the stability of the single crystal growth process can be improved, which is the effect of the present invention.

[0013] The metal foil to be processed can be a copper foil or a nickel foil. Thus, after processing, the metal foil to be processed can form a single-crystal metal foil, which serves as a growth substrate for two-dimensional materials.

[0014] The predetermined pressure can be 1 × 10⁻¹ to 1 × 10⁻⁴ Torr. This avoids undesirable reactions between air and the metal foil to be treated, thus improving the quality of the single-crystal metal foil.

[0015] The support may include a base, a support column, and an extension rod; one end of the support column stands on the base, and the other end of the support column is connected to the extension rod; the metal foil to be treated is placed on the extension rod, so that at least a portion of the metal foil to be treated is suspended due to gravity. In this way, the metal foil to be treated can be prevented from contacting the base or the chamber, and the surface roughness of the single-crystal metal foil can be reduced by utilizing the weak gravity effect, thus improving the quality of the single-crystal metal foil.

[0016] The support may have two parallel extension rods with a maximum distance of 12-18 mm between them. This allows both ends of the metal foil to be processed to hang down under gravity without shrinking inward, thus improving the quality of the single-crystal metal foil.

Implementation Method

[0017] In order to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments of the present invention are described below in conjunction with the accompanying drawings; in addition, those symbols that are marked with the same symbols in different drawings are considered to be the same and their descriptions will be omitted.

[0018] Please refer to Figure 1. The manufacturing method of the single crystal metal foil of the present invention may include: a preparation step S1, a pressure reduction step S2, a heating step S3, an annealing step S4 and a cooling step S5.

[0019] In this preparation step S1, as shown in Figure 2, a metal foil F to be processed is placed on a support 1 so that at least a portion of the metal foil F is suspended due to gravity. The metal foil F to be processed can be, for example, a polycrystalline metal foil of copper or nickel, preferably a copper or nickel foil with a purity greater than 99%. The thickness of the metal foil F to be processed can be, for example, 50~150 μm, or 70~120 μm, or 75~100 μm. Then, the metal foil F to be processed, together with the support 1, is placed in a chamber C. The chamber C can be any chamber in which the pressure and temperature inside the chamber can be adjusted, for example, it can be the reaction chamber of a chemical vapor deposition (CVD) apparatus, especially the reaction furnace tube of a horizontal CVD apparatus. By using the reaction furnace tube of a horizontal CVD apparatus, heating can be performed uniformly, reducing the thermal gradient, thereby improving the quality of the obtained single-crystal metal foil.

[0020] In detail, as shown in Figure 3, the support 1 may include a base 11, a support column 12 and an extension rod 13; one end of the support column 12 stands on the base 11, and the other end of the support column 12 is connected to the extension rod 13. The metal foil F to be processed can be placed on the extension rod 13, so that at least a portion of the metal foil F to be processed is suspended due to gravity.

[0021] Preferably, as shown in Figure 3, the base 11 is approximately flat and has two extending ends; each end of the base 11 has two support columns 12; the bracket 1 has two extension rods 13, which are respectively connected to the support columns 12 located at both ends of the base 11. Preferably, the two extension rods 13 are parallel to each other, and there is a maximum distance D1 between the two extension rods 13, which can be 12~18 mm or 15 mm. There is an axial distance D2 between the axes of the two extension rods 13, which can be 9~15 mm or 12 mm. In the preparation step S1, as shown in Figure 2, the metal foil F to be processed can be placed on the parallel two extension rods 13, so that both ends of the metal foil F to be processed are suspended due to gravity. By defining the maximum spacing D1 and the axial spacing D2 within a specific range, it can be ensured that the two ends of the metal foil F to be processed hang over without shrinking inward, thereby improving the quality of the produced single-crystal metal foil; and it can also increase the hanging area of ​​the metal foil F to be processed, thereby improving the manufacturing efficiency of the single-crystal metal foil. The support 1 can be made of alumina, for example, thereby preventing undesirable chemical reactions between the metal foil F to be processed and the support 1.

[0022] In the depressurization step S2, the air pressure in chamber C is reduced to a predetermined pressure. This predetermined pressure is lower than atmospheric pressure, thereby preventing an undesirable reaction between the air in chamber C and the metal foil F to be treated during the subsequent heating process. This predetermined pressure can be, for example, 1 × 10⁻¹ to 1 × 10⁻⁴ Torr, or it can be 1 × 10⁻³ Torr; the present invention is not limited thereto.

[0023] In the heating step S3, an inert gas is introduced into the chamber C at a first inert gas flow rate, and the temperature inside the chamber C is increased to a predetermined temperature. In this invention, the inert gas can be any one selected from the group consisting of helium, nitrogen, and argon, preferably argon. The first inert gas flow rate can be 1~500 sccm (standard milliliters per minute), or 10~250 sccm, or 20~100 sccm, or 30~70 sccm, or 50 sccm. The predetermined temperature can be 1000~1500℃. Specifically, when the metal foil F to be processed is copper foil, the predetermined temperature can be 1000~1100℃, or 1020~1040℃, or 1030℃; when the metal foil F to be processed is nickel foil, the predetermined temperature can be 1300~1500℃, or 1350~1450℃, or 1400℃.

[0024] In the annealing step S4, at the predetermined temperature, the inert gas is introduced into the chamber C at a second inert gas flow rate, and hydrogen is simultaneously introduced into the chamber C at a hydrogen flow rate, and maintained for a predetermined time. Preferably, the second inert gas flow rate is greater than the first inert gas flow rate. The second inert gas flow rate can be 200~500 sccm, or 300~500 sccm, or 400~500 sccm, or 450~500 sccm, or 500 sccm. The hydrogen flow rate can be 1~200 sccm, or 50-200 sccm, or 100-200 sccm, or 150-200 sccm, or 200 sccm. The predetermined time can be 8~22 hours, or 12~18 hours. Specifically, when the metal foil F to be processed is copper foil, the predetermined time can be 8 to 16 hours, or 10 to 14 hours, or 12 hours; when the metal foil F to be processed is nickel foil, the predetermined time can be 14 to 22 hours, or 16 to 20 hours, or 18 hours.

[0025] In the manufacturing method of the single-crystal metal foil of the present invention, during the annealing step S4, the grains of the polycrystalline metal foil undergo recombination and merging under the influence of high temperature and gas environment to form a (111) oriented single-crystal metal foil. Furthermore, by using the support 1, at least a portion of the metal foil F to be processed can be suspended during the high-temperature annealing process. This not only prevents the metal foil F from contacting the base 11 or the chamber C and affecting grain growth, but also effectively reduces the surface roughness of the obtained single-crystal metal foil by utilizing the weak gravity effect. In addition, by using a combination of inert gas (e.g., argon) and hydrogen and appropriately controlling the flow rates of the inert gas and hydrogen, the present invention enables stable growth of the single-crystal structure, thereby obtaining a high-quality single-crystal metal foil.

[0026] In the cooling step S5, the inert gas is introduced into the chamber C at a third inert gas flow rate, while the chamber C is allowed to cool naturally to room temperature. Preferably, the third inert gas flow rate is less than the second inert gas flow rate. Furthermore, the third inert gas flow rate can be the same as the first inert gas flow rate, that is, the third inert gas flow rate can be 1~500 sccm, or 10~250 sccm, or 20~100 sccm, or 30~70 sccm, or 50 sccm. After the cooling step S5 is completed, a high-quality (111) crystal orientation single-crystal metal foil can be formed on the overhanging portion of the metal foil F to be treated.

[0027] Additionally, referring to Figure 3, the support 1 used in the method for manufacturing the single-crystal metal foil of the present invention may further include an insertion portion 14 protruding from at least one end of the base 11 to facilitate the insertion of the support 1 into the chamber C. The insertion portion 14 may be, for example, a triangular structure formed by connecting two rods, but any structure that facilitates the insertion of the support 1 into the chamber C is acceptable and is not limited by the present invention.

[0028] Furthermore, referring to Figure 4, which shows another embodiment of the support 1 used in the manufacturing method of the single-crystal metal foil of the present invention. In this embodiment, the base 11 is approximately flat and has two extending ends; each end of the base 11 has a support column 12, and the support column 12 is Y-shaped. The support 1 also has two extension rods 13, which are respectively connected to the support columns 12 located at both ends of the base 11. Specifically, the two ends of the Y-shaped structure of the support column 12 are respectively connected to the two extension rods 13. Preferably, the two extension rods 13 are parallel to each other, and there is a maximum distance D1 between the two extension rods 13, which can be 12~18 mm or 15 mm. There is an axial distance D2 between the axes of the two extension rods 13, which can be 9~15 mm or 12 mm. In this type of bracket 1, by having only one support column 12 at each end of the base 11, the width of the base 11 can be reduced, so as to insert the bracket 1 into the chamber C.

[0029] In summary, the single-crystal metal foil manufacturing method of the present invention, by employing the support structure that makes the metal foil to be treated hang, can promote single crystal growth during the annealing process by utilizing the weak gravity effect, which is beneficial for manufacturing large-area single-crystal metal foil on an industrial scale, and can effectively reduce the adverse effects caused by the contact between the metal foil to be treated and the chamber, thereby improving the quality of the obtained single-crystal metal foil; and by controlling the flow rate and ratio of inert gas and hydrogen, the stability of the single crystal growth process can be improved, which are the effects of the present invention.

[0030] Although the present invention has been disclosed using the above preferred embodiments, it is not intended to limit the present invention. Any modifications and alterations made by those skilled in the art to the above embodiments without departing from the spirit and scope of the present invention shall still fall within the scope of the technology protected by the present invention. Therefore, the scope of protection of the present invention shall include all changes within the meaning and equivalent scope of the appended claims. [Simplified Explanation of the Diagram]

[0031] [Figure 1] Flowchart of the manufacturing method of the single-crystal metal foil of the present invention. [Figure 2] Schematic diagram of an implementation of the manufacturing method of the single-crystal metal foil of the present invention. [Figure 3] Perspective view of the support used in the manufacturing method of the single-crystal metal foil of the present invention. [Figure 4] Perspective view of another aspect of the support used in the manufacturing method of the single-crystal metal foil of the present invention.

Claims

1. A method for manufacturing a single-crystal metal foil, comprising: A metal foil to be treated is placed on a support, so that at least a portion of the metal foil is suspended due to gravity, and the metal foil to be treated, together with the support, is placed in a chamber; the gas pressure in the chamber is brought to a predetermined pressure; an inert gas is introduced into the chamber at a first inert gas flow rate, and the ambient temperature in the chamber is brought to a predetermined temperature; at the predetermined temperature, the inert gas is introduced into the chamber at a second inert gas flow rate, and hydrogen is introduced into the chamber at a hydrogen flow rate, and this is maintained for a predetermined time; and the inert gas is introduced into the chamber at a third inert gas flow rate, and the chamber is allowed to cool naturally; wherein, the first inert gas flow rate is 1~500 sccm, the predetermined temperature is 1000~1500℃, the second inert gas flow rate is 200~500 sccm, the hydrogen flow rate is 1~200 sccm, the predetermined time is 8~22 hours, and the third inert gas flow rate is 1~500 sccm.

2. The method for manufacturing a single-crystal metal foil as claimed in claim 1, wherein, The metal foil to be processed is either copper foil or nickel foil.

3. The method for manufacturing a single-crystal metal foil as claimed in claim 1, wherein, The predetermined pressure is 1 × 10⁻¹ to 1 × 10⁻⁴ Torr.

4. A method for manufacturing a single-crystal metal foil as claimed in claim 1, wherein, The support includes a base, a support column, and an extension rod; one end of the support column stands on the base, and the other end of the support column is connected to the extension rod; the metal foil to be processed is placed on the extension rod, so that at least a portion of the metal foil to be processed is suspended due to gravity.

5. The method for manufacturing a single-crystal metal foil as described in claim 8, wherein, The bracket has two parallel extension rods with a maximum spacing of 12-18 mm between them.

Images