阅读说明：本技术 一种MgB2超导微桥的制备方法 (MgB2Preparation method of superconducting microbridge ) 是由 孔祥东 张新月 李艳丽 韩立 于 2021-07-23 设计创作，主要内容包括：本发明提供了一种MgB-(2)超导微桥的制备方法,属于超导微桥制备技术领域。本发明所述MgB-(2)超导微桥的制备方法包括以下步骤：采用聚焦离子束在裸衬底上直写制备出微桥结构；所述微桥结构的尺寸与MgB-(2)超导微桥的尺寸相同；采用混合物理化学气相沉积在所述微桥结构的表面沉积MgB-(2)超导薄膜,形成MgB-(2)超导微桥。本发明先制备微桥结构,后沉积MgB-(2)超导薄膜,可以有效避免超导薄膜受到损伤,进而确保超导微桥的性能。(The invention provides MgB 2 A preparation method of a superconducting microbridge belongs to the technical field of superconducting microbridge preparation. The MgB of the invention 2 The preparation method of the superconducting microbridge comprises the following steps: directly writing on a bare substrate by adopting a focused ion beam to prepare a micro-bridge structure; the size and MgB of the micro-bridge structure 2 The sizes of the superconducting microbridges are the same; depositing MgB on the surface of the micro-bridge structure by mixed physical-chemical vapor deposition 2 Superconducting thin film of MgB 2 A superconducting microbridge. The invention firstly prepares the micro-bridge structure and then deposits MgB 2 The superconducting film can effectively avoid the superconducting film from being damaged, and further ensures the performance of the superconducting microbridge.)

1. MgB₂The preparation method of the superconducting microbridge is characterized by comprising the following steps:

directly writing on a bare substrate by adopting a focused ion beam to prepare a micro-bridge structure; the size and MgB of the micro-bridge structure₂The sizes of the superconducting microbridges are the same;

depositing MgB on the surface of the micro-bridge structure by mixed physical-chemical vapor deposition₂Superconducting thin film of MgB₂A superconducting microbridge.

2. The method according to claim 1, wherein the reaction temperature of the hybrid physical chemical vapor deposition is 640-700 ℃.

3. The method according to claim 2, wherein the reaction temperature of the hybrid physical chemical vapor deposition is 660 to 680 ℃.

4. The method of any one of claims 1 to 3, wherein the reaction time of the hybrid physical chemical vapor deposition is 150 to 210 seconds.

5. The method according to claim 4, wherein the reaction time of the hybrid physical chemical vapor deposition is 150-190 s.

6. The preparation method according to claim 1, wherein diborane is used as a boron source in the hybrid physical chemical vapor deposition, and the flow rate of the diborane is 4-10 sccm.

7. The preparation method according to claim 1, wherein the vacuum degree of the reaction in the hybrid physical-chemical vapor deposition is 4.17 to 4.22 kPa.

8. The method of claim 1, wherein the MgB is deposited on the surface of the micro-bridge structure by hybrid physical-chemical vapor deposition₂The superconducting thin film includes the steps of: opening the reaction cabin, placing the substrate directly written with the microbridge structure in the center of the sample table, placing the Mg blocks on the sample table and around the substrate, and closing the reaction cabin; the reaction cabin is vacuumized by a mechanical pump, and the vacuum degree of the reaction cabin is kept<H is introduced at 7Pa₂Heating the sample stage when the vacuum degree of the reaction is reached, introducing diborane for reaction when the reaction temperature is reached, closing the diborane after the reaction is finished, closing the sample stage for heating, and closing the H₂And closing the mechanical pump.

9. The production method according to claim 1, wherein the bare substrate includes a SiC substrate.

10. The method according to claim 1, wherein the conditions for directly writing the micro-bridge structure on the bare substrate by using the focused ion beam comprise: the acceleration voltage of the ion beam is 30kV, and the beam current is 10-150 pA.

Technical Field

The invention relates to the technical field of superconducting microbridge preparation, in particular to MgB₂A preparation method of a superconducting microbridge.

Background

The terahertz wave band (the universal division standard is 0.1-10 THz frequency band, corresponding to the wavelength of 3 mm-30 microns) has important scientific significance and rich application prospect, plays an important role in radio astronomy and atmospheric physics, especially in research of the ozone layer, and has good application potential in the aspects of organism nondestructive testing, future wireless network and the like.

Currently, the common terahertz detectors mainly include coherent detection and incoherent detection. Coherent detection, which can detect the amplitude and phase of the measurement field, while incoherent detection can only detect the amplitude of the field, has higher sensitivity and higher spectral resolution and can obtain phase information of the signal compared with incoherent detection. Coherent detectors include the two classes of superconducting tunnel junction mixers (SIS) and superconducting thermal electronic mixers (HEB). The operating frequency of the SIS junction mixer is limited by the superconducting energy gap of the material, and the operating frequency of the HEB is not limited by the superconducting energy gap. In recent years, research on HEB has advanced significantly.

Superconducting HEBs mainly comprise two parts: the planar antenna is used for converging the radiated THz signals, and the superconducting microbridge is used for detecting the THz signals. The superconducting microbridge is a key structure for preparing the HEB, and the operating temperature and the medium-frequency bandwidth of the HEB are determined by the superconducting transition temperature and the film thickness of the superconducting microbridge. In previous researches, the HEB is mainly based on a niobium nitride (NbN) thin film, wherein the frequency gain bandwidth can only reach about 3GHz, which is difficult to satisfy high-frequency spectrum observation, and the lower superconducting transition temperature of NbN increases the refrigeration cost of the device working environment. MgB₂The superconducting film has the advantages of high superconducting transition temperature (40K), strong current carrying capacity, short electroacoustic interaction time and the like, has great potential in widening the intermediate frequency band of HEB and improving the working temperature thereof, so that MgB is adopted₂The superconducting ultra-thin film is necessary to prepare a superconducting microbridge.

Currently MgB₂The preparation of the superconducting microbridge is realized according to the sequence of growing a superconducting film and then performing micro-machining on the film, because the surface treatment, exposure or etching and the like of the film are involved in the micro-machining process, the film can be irreversibly damaged, the superconducting performance of the film microbridge is damaged, even the microbridge is quenched, and the performance of a device of the HEB is seriously influenced.

Disclosure of Invention

The invention aims to provide MgB₂The preparation method of the superconducting microbridge can effectively prevent the superconducting film from being damaged, thereby ensuring the performance of the superconducting microbridge.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides MgB₂The preparation method of the superconducting microbridge comprises the following steps:

directly writing on a bare substrate by adopting a focused ion beam to prepare a micro-bridge structure; the size and MgB of the micro-bridge structure₂The sizes of the superconducting microbridges are the same;

depositing MgB on the surface of the micro-bridge structure by mixed physical-chemical vapor deposition₂Superconducting thin film of MgB₂A superconducting microbridge.

Preferably, the reaction temperature of the mixed physical-chemical vapor deposition is 640-700 ℃.

Preferably, the reaction temperature of the mixed physical chemical vapor deposition is 660-680 DEG C

Preferably, the reaction time of the mixed physical chemical vapor deposition is 150-210 s.

Preferably, the reaction time of the mixed physical chemical vapor deposition is 150-190 s.

Preferably, diborane is used as a boron source in the mixed physical chemical vapor deposition, and the flow rate of the diborane is 4-10 sccm.

Preferably, the vacuum degree of the reaction during the mixed physical-chemical vapor deposition is 4.17-4.22 kPa.

Preferably, the MgB is deposited on the surface of the micro-bridge structure by adopting mixed physical-chemical vapor deposition₂The superconducting thin film includes the steps of: opening the reaction cabin, placing the substrate directly written with the microbridge structure in the center of the sample table, placing the Mg blocks on the sample table and around the substrate, and closing the reaction cabin; the reaction cabin is vacuumized by a mechanical pump, and the vacuum degree of the reaction cabin is kept<H is introduced at 7Pa₂Heating the sample stage when the vacuum degree of the reaction is reached, introducing diborane for reaction when the reaction temperature is reached, closing the diborane after the reaction is finished, closing the sample stage for heating, and closing the H₂And closing the mechanical pump.

Preferably, the bare substrate comprises a SiC substrate.

Preferably, the conditions for preparing the microbridge structure by directly writing on the bare substrate by using the focused ion beam include: the acceleration voltage of the ion beam is 30kV, and the beam current is 10-150 pA.

The invention provides MgB₂The preparation method of the superconducting microbridge comprises the following steps: directly writing on a bare substrate by adopting a focused ion beam to prepare a micro-bridge structure; the size and MgB of the micro-bridge structure₂The sizes of the superconducting microbridges are the same; depositing MgB on the surface of the micro-bridge structure by mixed physical-chemical vapor deposition₂Superconducting thin film of MgB₂A superconducting microbridge. The invention firstly prepares the micro-bridge structure and then deposits MgB₂The superconducting film can effectively avoid the superconducting film from being damaged, and further ensures the performance of the superconducting microbridge.

The invention adopts Focused Ion Beam (FIB) direct writing technology to process the micro-bridge structure, and can prepare the micro-bridge structure with accurate appearance and size on a bare substrate by accurately controlling the size of the beam current, the etching time and the like, and the size precision can reach sub-10 nm.

Further, the present invention can obtain high quality MgB by controlling the conditions of Hybrid Physical Chemical Vapor Deposition (HPCVD)₂A superconducting thin film.

Drawings

FIG. 1 is a schematic view of a micro-bridge structure design;

FIG. 2 is a schematic diagram of FIB direct-write fabrication of a microbridge structure;

FIG. 3 is a schematic diagram of the principle of hybrid physical chemical vapor deposition;

FIG. 4 is a deposition of MgB₂MgB formed after superconducting thin film₂A schematic structural diagram of a superconducting microbridge;

FIG. 5 is MgB prepared in example 1₂A physical map of the superconducting microbridge;

FIG. 6 is MgB prepared in example 1₂The superconducting transition temperature (R-T) curve of the superconducting microbridge.

Detailed Description

The invention provides MgB₂The preparation method of the superconducting microbridge comprises the following steps:

directly writing on a bare substrate by adopting a focused ion beam to prepare a micro-bridge structure; the size and MgB of the micro-bridge structure₂Of superconducting microbridgesThe sizes are the same;

depositing MgB on the surface of the micro-bridge structure by mixed physical-chemical vapor deposition₂Superconducting thin film of MgB₂A superconducting microbridge.

The invention adopts focused ion beams to directly write on a bare substrate to prepare a micro-bridge structure.

Before the micro-bridge structure is prepared, the invention preferably designs the micro-bridge structure and the size according to the actual requirement, and then adopts the focused ion beam to process on the bare substrate. The present invention preferably designs the microbridge structure on a computer. As shown in fig. 1, where L is the microbridge length and W is the microbridge width.

In the present invention, the size of the microbridge structure and MgB₂The dimensions of the superconducting microbridges are the same. The invention is directed to the MgB₂The dimensions of the superconducting microbridge are not particularly critical and dimensions well known in the art are suitable for use with the present invention. In an embodiment of the present invention, the MgB₂The dimensions of the superconducting microbridge are 0.5 μm wide by 1 μm long (W.times.L), 0.5 μm wide by 2 μm long, or 0.5 μm wide by 0.5 μm long.

After the size of the micro-bridge structure is designed, the invention adopts focused ion beams to directly write on a bare substrate to prepare the micro-bridge structure.

The invention has no special requirement on the condition of directly writing and preparing the micro-bridge structure on the bare substrate by adopting the focused ion beam, and can prepare the micro-bridge structure with target appearance and size. In the invention, the acceleration voltage of the ion beam is preferably 30kV, and the beam current is preferably 10-150 pA, and more preferably 50-100 pA. In the examples of the present invention, the specific conditions are: the acceleration voltage of the ion beam is 30kV, and the beam current is 10pA, 70pA or 150 pA.

FIG. 2 is a schematic diagram of the fabrication of a microbridge structure using FIB direct write. The white area is a portion directly written by FIB.

After the micro-bridge structure is obtained, the invention adopts mixed physical-chemical vapor deposition to deposit MgB on the surface of the micro-bridge structure₂Superconducting thin film of MgB₂A superconducting microbridge.

In the invention, the surface adopting mixed physical chemical vapor deposition on the micro-bridge structureSurface deposition of MgB₂The superconducting thin film preferably includes the steps of: opening the reaction cabin, placing the substrate directly written with the microbridge structure in the center of the sample table, placing the Mg blocks on the sample table and around the substrate, and closing the reaction cabin; the reaction cabin is vacuumized by a mechanical pump, and the vacuum degree of the reaction cabin is kept<H is introduced at 7Pa₂Heating the sample stage when the vacuum degree of the reaction is reached, introducing diborane for reaction when the reaction temperature is reached, closing the diborane after the reaction is finished, closing the sample stage for heating, and closing the H₂And closing the mechanical pump.

In the invention, the reaction temperature of the mixed physical-chemical vapor deposition is preferably 640-700 ℃, more preferably 660-680 ℃, and further preferably 665-675 ℃; the reaction time of the mixed physical chemical vapor deposition is preferably 150-210 s, more preferably 160-200 s, and further preferably 170-190 s; the mixed physical chemical vapor deposition preferably adopts diborane as a boron source, and the flow rate of the diborane is preferably 4-10 sccm, more preferably 5-9 sccm, and further preferably 6-8 sccm. In the invention, the degree of vacuum of the reaction during the mixed physical chemical vapor deposition is preferably 4.17 to 4.22kPa, more preferably 4.18 to 4.21kPa, and even more preferably 4.19 to 4.20 kPa.

In the present invention, the schematic diagram of the hybrid physical chemical vapor deposition is shown in FIG. 3, and MgB obtained after deposition₂The schematic structure of the superconducting microbridge is shown in FIG. 4.

The invention can obtain high-quality MgB by controlling the conditions of mixed physical chemical vapor deposition (HPCVD)₂A superconducting thin film.

The MgB provided by the invention is combined with the following embodiments₂The preparation of the superconductive microbridges is explained in detail, but they are not to be understood as limiting the scope of protection of the invention.

Example 1

(1) Designing the size of the microbridge to be 0.5 Mum multiplied by 1 Mum, namely the length of the microbridge is 1 Mum and the width of the microbridge is 0.5 Mum;

(2) clean 5 x 5mm²Putting the SiC substrate into an FIB/SEM dual-beam system, setting the acceleration voltage of an ion beam to be 30kV and the beam current to be 70pA,etching a microbridge with the diameter of 0.5 Mum multiplied by 1 Mum on the SiC substrate after focusing;

(3) opening a reaction cabin, uniformly placing 6 cut Mg blocks (each Mg block has the mass of about 2-4 g and the purity of not less than 99.99%) on a sample table, and placing the SiC substrate etched to form the microbridge in the step (2) in the center of the sample table;

(4) closing the reaction chamber, opening the mechanical pump to pump the vacuum of the reaction chamber until the vacuum is obtained<H is introduced at 7Pa₂；

(5) Heating the sample stage when the vacuum degree (or background pressure) is about 4.17 kPa;

(6) when the temperature reaches 665 ℃, diborane is introduced, the flow rate is 4sccm, and then chemical reaction is carried out to generate MgB₂；

(7) After 2min30s, the diborane is turned off, the sample stage heating is turned off, and the H is turned off₂Closing the mechanical pump;

(8) the coating was completed to obtain MgB of 0.5. mu. m.times.1 μm in size₂The superconducting microbridge is shown in figure 5. For MgB prepared in example 1₂Superconducting test is carried out on the superconducting microbridge to obtain MgB₂The R-T curve of the superconducting microbridge is shown in FIG. 6, and FIG. 6 shows that MgB₂The zero resistance transition temperature of the superconducting microbridge is 37K, which shows that the superconducting microbridge has good superconducting performance.

Example 2

(1) Designing the size of the microbridge to be 0.5 Mum multiplied by 2 Mum, namely the length of the microbridge is 2 Mum and the width of the microbridge is 0.5 Mum;

(2) clean 5 x 5mm²Putting the SiC substrate into an FIB/SEM dual-beam system, setting the acceleration voltage of an ion beam to be 30kV and the beam current to be 150pA, and etching a microbridge with the size of 0.5 Mum multiplied by 2 Mum on the SiC substrate after focusing;

(3) opening a reaction cabin, uniformly placing 6 cut Mg blocks (each Mg block has the mass of about 2-4 g and the purity of not less than 99.99%) on a sample table, and placing the SiC substrate etched to form the microbridge in the step (2) in the center of the sample table;

(4) closing the reaction chamber, opening the mechanical pump to pump the vacuum of the reaction chamber until the vacuum is obtained<H is introduced at 7Pa₂；

(5) Heating the sample stage when the vacuum degree (or background pressure) is changed to 4.17 kPa;

(6) when the temperature reaches 640 ℃, diborane is introduced with the flow rate of 6sccm, and chemical reaction can occur to generate MgB₂；

(7) After 190s, the diborane is turned off, the sample stage is turned off, the heating is stopped, and the H is turned off₂Closing the mechanical pump;

(8) the coating was completed to obtain MgB of 0.5. mu. m.times.2 μm in size₂The zero resistance transition temperature of the superconducting microbridge is 36K, which shows that the superconducting microbridge has good superconducting performance.

Example 3

(1) Designing the size of the microbridge to be 0.5 mu m multiplied by 0.5 mu m, namely the length of the microbridge is 0.5 mu m and the width of the microbridge is 0.5 mu m;

(2) clean 5 x 5mm²Putting the SiC substrate into an FIB/SEM dual-beam system, setting the acceleration voltage of an ion beam to be 30kV and the beam current to be 10pA, and etching a microbridge with the size of 0.5 Mum multiplied by 0.5 Mum on the SiC substrate after focusing;

(3) opening a reaction cabin, uniformly placing 6 cut Mg blocks (each Mg block has the mass of about 2-4 g and the purity of not less than 99.99%) on a sample table, and placing the SiC substrate etched to form the microbridge in the step (2) in the center of the sample table;

(4) closing the reaction chamber, opening a mechanical pump to pump the vacuum of the reaction chamber, and introducing H2 when the vacuum of the reaction chamber is less than 7 Pa;

(5) heating the sample stage when the vacuum degree (or background pressure) is changed to 4.22 kPa;

(6) when the temperature reaches 700 ℃, diborane is introduced with the flow rate of 10sccm, and chemical reaction can occur to generate MgB₂；

(7) After 190s, the diborane is turned off, the sample stage is turned off, the heating is stopped, and the H is turned off₂Closing the mechanical pump;

(8) the coating was completed to obtain MgB of 0.5. mu. m.times.0.5. mu.m in size₂The zero resistance transition temperature of the superconducting microbridge is 35K, which shows that the superconducting microbridge has good superconducting performance.

As can be seen from the above examples, the present invention provides a MgB₂The preparation method of the superconducting microbridge can effectively prevent the superconducting film from being damaged, thereby ensuring the performance of the superconducting microbridge.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.