Topological insulator nanopore size regulation and control method based on thickness-diameter ratio feedback

Abstract

The invention discloses a topological insulator Bi2Te3 nanopore size regulation and control method based on thickness-diameter ratio feedback, and belongs to the field of two-dimensional material nanometer manufacturing. Comprising the following steps: step 1, placing a sample in a transmission electron microscope, and prefabricating nanopores with the diameter of 1-5nm in a bismuth telluride film with the thickness of 2-10nm by utilizing a converged electron beam; step 2, performing irradiation by using an electron beam with 300kV acceleration voltage, wherein the beam density is controlled to be 1.54 * 10 < 5 > A.m <-2 >; 3, feeding back the regulation and control size based on the ratio of the initial aperture of the nanopore to the thickness of the material, and when the thickness-diameter ratio is smaller than 0.5, realizing aperture shrinkage or expansion by adjusting the beam density; and when the thickness-diameter ratio is greater than 0.5, the electron beam irradiation only enables the aperture to be enlarged, and the aperture cannot be shrunk. The method does not need chemical reagents, is green and environment-friendly, can directionally regulate and control the size of the bismuth telluride nanopore, and is suitable for preparing topological quantum devices, nanofiltration membranes and thermoelectric nanostructures.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanofabrication technology, and in particular to a topological insulator nanopore size regulation method based on thickness-diameter ratio feedback. BACKGROUND

[0002] Topological insulator is a material with special electronic properties, which is insulating inside and has a conductive topological surface state on the surface or boundary. As a member of the topological insulator family, bismuth telluride is a thermoelectric material with broad application prospects at near room temperature. In order to improve the thermoelectric performance of this material, its size and heat transfer should be reduced. Studies have shown that the formation of optimized nanopores in the material can improve the thermoelectric performance, reduce the thermal conductivity while maintaining the electrical performance (Applied Physics Letters 98, 023114, 2011). Therefore, two-dimensional nanosheets with nanopores are an ideal structure, because the nanopores will destroy the heat transfer and reduce the lattice thermal conductivity, thereby improving the thermoelectric figure of merit, and are expected to be used in thermoelectric devices (Scientific Reports 9, 10790, 2019). In addition, studies have found that introducing nanopore structures on the surface of topological insulators not only does not destroy the topological surface state, but also significantly enhances the weak antilocalization effect dominated by the surface state, and doubles the phase coherence length, making it have application potential in low-energy electronic and spin electronic devices (Physical Review Materials 7(6), 064202, 2023).

[0003] In the existing nanopore regulation methods, electrochemical deposition can accurately reduce the pore size to 0.5-2 nm with good repeatability, but is limited to conductive substrates; voltage or ion pulse hole expansion can expand the pore size from 2 nm to tens of nanometers in situ in solid-state membranes, and the operation is fast, but defects are easily introduced. Template patterning combined with photolithography can achieve 20-250 nm graded holes, which is suitable for batch manufacturing, but the process is complex and the cost is high. Chemical etching or heat treatment expands the hole by acid, base or annealing, which is suitable for metal oxides, ceramics, etc., and the pore size can be adjusted to 10-150 nm, which is low in cost but poor in uniformity.

[0004] For topological insulators (such as bismuth telluride) nanopores, it is not clear whether the size regulation by electron beam irradiation depends on a similar thickness-diameter ratio relationship, and there is currently a lack of a directional regulation method based on thickness-diameter ratio feedback, which limits the precise control of the contraction and expansion of bismuth telluride nanopores and restricts its application in nanodevices. Therefore, there is an urgent need for a method that can regulate the size of bismuth telluride nanopores based on thickness-diameter ratio feedback. SUMMARY

[0005] Technical problem: In order to realize the directional regulation of the nanometer hole size of the topological insulator (bismuth telluride), the present application provides a topological insulator nanometer hole size regulation method based on the thickness-diameter ratio feedback, which realizes the accurate regulation of the nanometer hole size of the topological insulator bismuth telluride based on the feedback of the material thickness-diameter ratio (the ratio of the initial hole diameter and the material thickness d / h) through electron beam irradiation in a transmission electron microscope. The problem that the nanometer hole size of bismuth telluride cannot be regulated based on the thickness-diameter ratio in the prior art is solved, and the method is simple and controllable. The technology does not need to be limited to a conductive base and does not need to introduce chemicals, and can realize regulation only through electron beam irradiation.

[0006] Technical scheme:

[0007] According to a first aspect of the present application, the present application provides a topological insulator nanometer hole size regulation method based on the thickness-diameter ratio feedback, which regulates the nanometer hole size on the topological insulator material by combining the thickness-diameter ratio d / h and using electron beam irradiation.

[0008] In some embodiments of the present application, the two-dimensional topological insulator material is a two-dimensional bismuth telluride material.

[0009] In some embodiments of the present application, the two-dimensional bismuth telluride material has a thickness h of 2-10 nm (which can be adjusted by a person skilled in the art according to actual needs, and 6 nm is taken as an example in the present application).

[0010] The nanometer hole in the present application is a nanometer hole with different initial hole diameters constructed on the same region of the two-dimensional bismuth telluride, and the initial hole diameter (d) of the nanometer hole ranges from 1.5 nm to 4.5 nm.

[0011] In some embodiments of the present application, the electron beam irradiation is performed in a transmission electron microscope (TEM), the acceleration voltage of the electron is 300 kV, the beam current density ranges from 1.54×10 5 to 2.46×10 6 A·m -2 , and the irradiation time is determined according to the hole diameter regulation requirement (the single irradiation time is about 50-220 s in the present application).

[0012] In some embodiments of the present application, when d / h≤0.5, the shrinkage or expansion of the nanometer hole diameter can be realized by adjusting the beam current density; in some specific embodiments, when d / h≤0.5, the beam current density is less than 3×10 5 A·m -2 The nanometer hole diameter can be shrunk by irradiation, and when the beam current density is greater than 6×10 5 A·m -2The nanopore can be enlarged by irradiation.

[0013] In some embodiments of the present application, when d / h>0.5, the electron beam irradiation only enlarges the nanopore aperture, and cannot achieve shrinkage.

[0014] According to a second aspect of the present application, the present application provides a use of the topological insulator nanopore material prepared by the method of the first aspect, for preparing topological quantum devices, nanofiltration membranes and high-performance thermoelectric nanostructure devices.

[0015] The present application has the following beneficial effects:

[0016] (1) The present application realizes in-situ, reversible and precise regulation of the size of the bismuth telluride nanopore by introducing "thickness-to-diameter ratio (d / h)" as a real-time feedback parameter: when d / h≤0.5, the shrinkage or enlargement of the nanopore aperture can be achieved by adjusting the beam current density, while when d / h>0.5, the electron beam irradiation only enlarges the nanopore aperture, and cannot shrink; therefore, the desired aperture size can be obtained in the range of 0-5 nm.

[0017] (2) The present method does not require any chemical reagents, is green and environmentally friendly, is simple to operate, and the entire process can be completed in-situ in a transmission electron microscope, avoiding transfer contamination;

[0018] (3) The present application is suitable for Bi2Te3 thin films with a thickness of 2-10 nm, and can be extended to other two-dimensional topological insulators, providing a universal platform for controllable preparation of topological quantum devices, nanofiltration membranes and high-performance thermoelectric nanostructures. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 : Transmission electron microscopy characterization results of the aperture change process of initial nanopores with diameters of 1.8 nm (d / h=0.3) and 1.4 nm (d / h=0.23) under electron beam irradiation (A: beam current density of 1.54×10 5 A·m -2 , B: beam current density of 2.46×10 6 A·m -2 ).

[0020] Figure 2 : Transmission electron microscopy characterization results of the aperture change process of initial nanopores with diameters of 3.5 nm (d / h=0.58) and 4.2 nm (d / h=0.7) under electron beam irradiation (A: beam current density of 1.54×10 5 A·m -2 , B: beam current density of 2.73×10 5 A·m -2 ).

[0021] Figure 3 The initial nanopore with a pore size range of 1.5-4.5 nm shrinks under electron beam irradiation (beam current density: 1.54*10 5 A·m -2 The scatter plot of the pore size change with time shows that the pore shrinks when d / h≤0.5 and expands when d / h>0.5. DETAILED DESCRIPTION

[0022] The present application is based on a topological insulator nanopore size regulation method with thickness-to-diameter ratio feedback, which comprises the following steps:

[0023] Step 1: Place the sample in a transmission electron microscope, and use a convergent electron beam to preform a nanopore with a diameter of 1-5 nm on a bismuth telluride film with a thickness of 2-10 nm; Step 2: irradiate with an electron beam at an acceleration voltage of 300 kV, and control the beam current density; Step 3: regulate the size based on the ratio of the initial pore size of the nanopore to the thickness of the material, when the thickness-to-diameter ratio is less than 0.5, the pore size can be shrunk or expanded by adjusting the beam current density; when the thickness-to-diameter ratio is greater than 0.5, the electron beam irradiation only expands the pore size and cannot shrink it.

[0024] Material and equipment information: Except otherwise specified in the present application, the materials and equipment used in the present application are all conventional materials or equipment.

[0025] The two-dimensional bismuth telluride sample is a bismuth telluride two-dimensional single crystal from Nanjing Muke Nanotechnology Co., Ltd.; and the transmission electron microscope is FEI Titan 80-300.

[0026] Example 1:

[0027] Place a 6-nm-thick two-dimensional bismuth telluride sample in a transmission electron microscope (TEM), and use a convergent electron beam to construct two initial nanopores with diameters of about 1.8 nm (d / h=0.3) and 1.4 nm (d / h=0.23) on the sample, with an electron acceleration voltage of 300 kV.

[0028] Set the beam current density of the electron beam to 1.54*10 5 A·m -2 Irradiate the initial nanopore with a diameter of about 1.8 nm, and simultaneously observe the change of the nanopore in real time by TEM, as shown in FIG. Figure 1 A. After 149 s of irradiation, the nanopore diameter gradually shrinks to 0 nm.

[0029] Set the beam current density of the electron beam to 2.46*10 6 A·m -2 Irradiate the initial nanopore with a diameter of about 1.4 nm, and simultaneously observe the change of the nanopore in real time by TEM, as shown in FIG. Figure 1As shown in B, after 51 seconds of irradiation, the pore size of the nanopores gradually increased until it reached 3.5 nm.

[0030] Therefore, when the initial thickness-to-diameter ratio d / h ≤ 0.5, the nanopores can be harvested or expanded by adjusting the beam density.

[0031] Example 2:

[0032] A two-dimensional bismuth telluride sample with a thickness of 6 nm was placed in a transmission electron microscope (TEM) with an electron acceleration voltage of 300 kV. Two initial nanopores with diameters of approximately 3.5 nm (d / h = 0.58) and 4.2 nm (d / h = 0.7) were constructed in the same region using a converging electron beam.

[0033] The electron beam current density is set to 1.54 × 10⁻⁶. 5 A·m -2 An initial nanopore with a diameter of approximately 3.5 nm was irradiated, and changes in the nanopore were observed in real time using TEM. Figure 2 As shown in Figure A, after 219 s of irradiation, the pore size of the nanopores gradually increased to 3.9 nm.

[0034] The electron beam current density is set to 2.73 × 10⁻⁶. 5 A·m -2 An initial nanopore with a diameter of approximately 4.2 nm was irradiated, and changes in the nanopore were observed in real time using TEM. Figure 2 As shown in Figure B, after 57 seconds of irradiation, the pore size of the nanopores gradually increased to 4.5 nm.

[0035] Therefore, when the initial thickness-to-diameter ratio d / h > 0.5, electron beam irradiation, even at low intensity beam current density, can only increase the pore size of the nanopores, but cannot shrink them.

[0036] Example 3:

[0037] Multiple nanopores with initial pore sizes ranging from 1.5 nm to 4.5 nm were constructed on a 6 nm thick two-dimensional bismuth telluride substrate using a minimum beam current density of 1.54 × 10⁻⁶. 5 Electron beam irradiation was performed at A / m2 for approximately 150 seconds, and the aperture change process was recorded (e.g., ...). Figure 3 (As shown).

[0038] The results showed that for nanopores with an initial pore size of less than 3 nm (thickness-to-diameter ratio d / h ≤ 0.5), the pore size gradually decreased; for nanopores with an initial pore size of more than 3 nm (thickness-to-diameter ratio d / h > 0.5), the pore size gradually increased.

[0039] It is further proved that the electron beam irradiation can shrink the Bi2Te2.7nanopore when the thickness-diameter ratio is less than or equal to 0.5, and can only enlarge the nanopore when the thickness-diameter ratio is greater than 0.5, which is consistent with the results of Examples 1 and 2.

[0040] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are included in the protection scope of the present application.

Claims

1. A method for controlling the size of nanopores in topological insulator materials by feedback of the ratio of thickness to diameter, which combines the ratio of thickness to diameter (d / h) and electron beam irradiation to control the size of nanopores in topological insulator materials; wherein the ratio of thickness to diameter (d / h) is the ratio of the initial diameter of nanopores (d) to the thickness (h) of two-dimensional topological insulator materials. 2.The method of claim 1, wherein the two-dimensional topological insulator material is a two-dimensional bismuth telluride material. 3.The method of claim 2, wherein the two-dimensional bismuth telluride material has a thickness (h) of 2-10 nm. 4.The method of claim 2, wherein the initial diameter (d) of nanopores ranges from 1.5 nm to 4.5 nm. 5.The method of claim 2, wherein the electron beam irradiation is performed in a transmission electron microscope; and / or the acceleration voltage of electrons is 300 kV. 6.The method of claim 2, wherein when d / h≤0.5, the diameter of nanopores can be shrunk or expanded by adjusting the beam current density. and / or, the beam current density ranges from 1.54 x 10 5 ~ 2.46 x 10 6 A-m -2 . 8.The method of claim 2, wherein when d / h>0.5, the diameter of nanopores can only be expanded by electron beam irradiation, but cannot be shrunk.

7. The method of claim 6, wherein the beam current density is less than 3 x 10 5 A·m -2 The nanopore aperture can be shrunk by irradiation when the beam current density is greater than 6 x 10 5 A·m -2 The nanopore can be enlarged by irradiation. 9.The method of claim 2, comprising the following schemes: (1) placing a 6 nm thick two-dimensional bismuth telluride sample in a transmission electron microscope with an acceleration voltage of 300 kV, and using a convergent electron beam to construct two initial nanopores with diameters of about 1.8 nm and 1.4 nm on the sample; (2) placing a 6 nm thick two-dimensional bismuth telluride sample in a transmission electron microscope with an acceleration voltage of 300 kV, and using a convergent electron beam to construct two initial nanopores with diameters of about 3.5 nm and 4.2 nm on the same region of the sample; The beam current density of the electron beam was set to 1.54 x 10 5 A·m -2 The initial nanopore with a diameter of about 1.8 nm was irradiated, and the change of the nanopore was observed in real time by transmission electron microscopy. After 149 s of irradiation, the nanopore diameter gradually decreased to 0 nm. The beam current density of the electron beam was set to 2.46 x 10 6 A·m -2 The initial nanopore with a diameter of about 1.4 nm was irradiated while observing the change of the nanopore in real time by transmission electron microscopy. After 51 s of irradiation, the nanopore diameter gradually increased to 3.5 nm; or 10.Use of a topological insulator nanopore material prepared by the method of claim 1 in the preparation of topological quantum devices, nanofiltration membranes, and high-performance thermoelectric nanostructure devices. The beam current density of the electron beam was set to 1.54 x 10 5 A·m -2 The initial nanopore with a diameter of about 3.5 nm was irradiated, and the change of the nanopore was observed in real time by TEM. After 219 s of irradiation, the nanopore diameter gradually increased to 3.9 nm. The beam current density of the electron beam was set to 2.73 x 10 5 A·m -2 The initial nanopore having a diameter of about 4.2 nm was irradiated while observing the change in the nanopore in real time by transmission electron microscopy. After 57 s of irradiation, the nanopore diameter gradually increased up to 4.5 nm. ​

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