CN102020253A - Topological insulator material and preparation method thereof - Google Patents

Abstract

The invention provides a topological insulator material and a preparation method thereof, belonging to the field of preparation of new materials. The topological insulator material is a bamboo-shaped bismuth selenide nanostructure array composed of bamboo-shaped bismuth selenide nanostructures with uniform size. The invention adopts a template-assisted method to directly obtain a regular bamboo-shaped bismuth selenide (copper-doped) nanostructure array on the template, and the prepared nanomaterial has the topological insulation performance of the control material. Compared with the preparation of traditional bismuth selenide materials, the invention has the characteristics of simple process, low cost, one-time molding and the like.

Description

A kind of topological insulator material and preparation method thereof

technical field

The invention belongs to the field of preparation of nanometer materials, and in particular relates to a topological insulator material and a preparation method thereof.

Background technique

According to the different electronic state structures, materials in the traditional sense are divided into two categories: "metals" and "insulators". The topological insulator is a new quantum state of matter. The bulk electronic state of this state of matter is an insulator with an energy gap, while its surface is a metal state without an energy gap. Different from surface states caused by surface unsaturated bonds or surface reconstruction in the general sense, the surface metal state of topological insulators is completely determined by the topology of the bulk electronic state of the material, which is protected by symmetry, so it is basically not affected by Effects of impurities and disorder. It is precisely because of these important characteristics that topological insulators will be likely to obtain important applications in the development of electronic technology in the future, and have huge application potential. Finding a strong topological insulator material with a sufficiently large bulk energy gap and chemical stability has become an important focus and difficulty of people's attention.

In 2009, the Institute of Physics of the Chinese Academy of Sciences/Beijing National Laboratory of Condensed Matter Physics cooperated deeply with Stanford University to predict a new class of strong topological insulator material systems (mainly V-VI materials, such as Bi ₂ Se ₃ , Bi ₂ Te ₃ and Sb ₂ Te ₃ ). They systematically explored the physical mechanism of this kind of material becoming a strong topological insulator theoretically and computationally, gave the KP Hamiltonian describing the Dirac point, and calculated the APRES-like electron spectrum. This type of topological insulator material has unique advantages, that is, there is only one Dirac point in the surface state of this type of material, and it is the simplest strong topological insulator. This simplicity provides a good platform for the study of theoretical models. In addition, the bulk energy gap of this type of material is very large, especially Bi ₂ Se ₃ (0.3 electron volts), which is far beyond the room temperature energy scale, which also means that it is possible to realize spintronic devices with low energy consumption at room temperature (Zhong Fang, Shou - Cheng Zhang, et al., Nature Physics, 2009(5): 438-442).

At the same time of theoretical research, relevant experimental work has also made important progress. Professor MZ Hasan and RJ Cava of Princeton University in the United States observed the existence of surface state Dirac points in Bi ₂ Se ₃ (Y. Xia, D. Qian, D. Hsieh, L. Wray, A. Pal, H. Lin, A. Bansil, D. Grauer, YS Hor, RJ Cava, et al., Nature Physics, 2009(5): 398-402). Fang Zhong and Dai Xi's research group from Institute of Physics, Chinese Academy of Sciences cooperated with Professor ZXShen's research group from Stanford University to observe a single Dirac point on the surface of Bi ₂ Te ₃ material by using ARPES (YLChen, JGAnalytis, J.-H.Chu, ZKLiu, S.-K. Mo, XL Qi, HJ Zhang, DH Lu, X. Dai, Z. Fang, SC Zhang, IR Fisher, Z. Hussain, and Z.-X. Shen, Science, 2009(325): 178-181). In addition to the research on the topological insulating properties of bulk materials, the design and synthesis of small-scale and low-dimensional structure materials and the influence of size effects on electron spin and other properties are another important aspect of the development of this field. The synthesis of V-VI nanomaterials mainly includes solution phase synthesis, such as hydrothermal synthesis (Hongjie Zhang, et al., J.AM.CHEM.SOC., 2006 (128): 16490-16491), microwave synthesis (R. Harpeness, A.Gedanken, New J.Chem., 2003(27):1191-1193), electrochemical deposition (Xiaoguang Li, et al., J.Phys.Chem.B, 2005(109):1430-1432) and sonoelectrochemical deposition (Xiaofeng Qiu, Clemens Burda, Ruiling Fu, Lin Pu, Hongyuan Chen, and Junjie Zhu, J.AM.CHEM.SOC., 2004(126): 16276-16277), and gas phase synthesis, such as chemical Vapor deposition (Hongkun Park, et al., J.AM.CHEM.SOC., 2008, 130, 6252) and molecular beam epitaxy (MBE for short) (Kehui Wu, et al., Appl.Phys. Lett, 2009(95): 053114-1~3). In the traditional molecular beam epitaxy and chemical vapor deposition methods, due to the limitations of complex preparation processes, expensive material costs, and difficult post-processing processes, it is often difficult to efficiently synthesize a large number of small-sized low-dimensional topological insulator materials. Due to the advantages of simple devices, low material cost, low energy consumption, and easy design and synthesis of various complex structures by adjusting parameters such as voltage, the electrochemical method has been favored in the synthesis of V-VI low-dimensional and small-sized superlattice structures. More and more widespread attention (Wei Wang, Xiaoguang Li, et al., J.Am.Chem.Soc.2007(129): 6702-6703; Xincun Dou, Guanghai Li, et al., Nano Lett., 2008( 8): 1286-1290; Wei Wang, Xiaoguang Li, et al., J. Phys. Chem. C, 2008(112): 15190-15194; FH Xue, GT Fei, B. Wu, P. Cui, and LD Zhang, J . Am. Chem. Soc. 2005, 127(44), 15348-15349). However, the superlattice structures synthesized by current electrochemical methods (mainly template-assisted electrochemical deposition V-VI superlattice nanowire arrays) can only realize the radial dimension of the material (along the direction of nanowire growth). Regulation, the regulation of the axial size of different fragments (perpendicular to the growth direction of the nanowire), and even the selective preparation of a certain fragment have not been reported. And this part of the work is very important for the study of topological insulating properties of materials.

Contents of the invention

The object of the present invention is to provide a topological insulator material and a preparation method thereof. The topological insulator material is a bamboo-shaped bismuth selenide nanostructure array.

The bamboo-shaped bismuth selenide nanostructure array is composed of bamboo-shaped bismuth selenide nanostructures with uniform size, and the thickness of the bamboo-shaped bismuth selenide nanostructure array (that is, the length of the bamboo-shaped bismuth selenide (copper-doped) nanostructure ) can be 0.5-50 μm, wherein the outer diameter of the bamboo-shaped bismuth selenide nanostructure is 20-200nm, and the aspect ratio of the nanostructure is 2.5-2500.

Bamboo-like bismuth selenide nanostructures doped with copper.

The preparation of bamboo-shaped bismuth selenide (copper-doped) nanostructure array provided by the invention comprises:

A. The preparation of the electrolyte: the solute is bismuth sulfate, copper sulfate and selenous acid, and the solvent can be triethanolamine (Triethanolamine, abbreviated as TEA) and ethylenediaminetetraacetic acid disodium salt (abbreviated as EDTA- 2Na) mixed with water. The composition of the main reactants is shown in the table below:

B. Electrochemical device: the gold-plated anodized aluminum template (Anodic Aluminum Oxide, referred to as AAO, but not limited to the template) on the back is used as the working electrode, the anode is a platinum electrode, and the reference electrode is a saturated calomel electrode;

C. Deposition strategy: adopt multi-step current pulse deposition method (Multi Current Steps), design I ₁ =1×10 ^-6 ~ 9×10 ^-6 A/mm ² and I ₂ =1×10 ^-5 ~ 9×10 ^-5 A/mm ² Two-stage deposition process (as shown in Figure 1, T ₁ : T ₂ = 1: 1 to 4: 1, where T ₁ is composed of 1 to 6 current pulses), filling bismuth selenide inside the template pores Alternating structure of (Bi ₂ Se ₃ ) and copper-doped bismuth selenide (Bi _2-x Cu _x Se ₃ ), the deposition time is 0.5-5 hours;

D. The template is removed to obtain a bamboo-shaped bismuth selenide (copper-doped) nanostructure array.

Annealing the bamboo-shaped bismuth selenide (copper-doped) nanostructure array prepared by the above method can obtain a single crystal structure.

The annealing temperature is regulated by the following heating and constant temperature stages:

1) The starting temperature of the heating stage is selected from any temperature between 10°C and 25°C, and the termination temperature is selected from any temperature between 300-600°C; the heating rate in the heating stage is 1- 20℃/min;

2) The temperature of the constant temperature stage is the termination temperature described in 1); the time of the constant temperature stage is 0.5-10 hours.

The present invention has the following advantages:

Using the template-assisted method, the regular bamboo-shaped bismuth selenide (copper-doped) nanostructure array is directly obtained on the template. Compared with the preparation of traditional bismuth selenide materials, it has simple process, low cost, and one-time molding. Features: By adjusting the inventive process, bamboo-shaped bismuth selenide (copper-doped) nanostructure array layers with different aspect ratios and crystal forms can be obtained, and the topological insulation properties of the material can be adjusted accordingly.

Description of drawings

Fig. 1 is the deposition strategy adopted by the electrochemical deposition method described in the invention;

Fig. 2 is the scanning electron micrograph of the bamboo-shaped bismuth selenide (copper-doped) nanostructure prepared in embodiment 1;

3 is a scanning electron micrograph of the bamboo-shaped bismuth selenide (copper-doped) nanostructure prepared in Example 2.

Detailed ways

The following examples are only a detailed description of the present invention, and should not be construed as limiting the present invention.

The main steps of preparing the bamboo-shaped bismuth selenide (copper-doped) nanostructure array in the embodiment of the present invention are as follows:

The aluminum oxide template with a thickness of 10-100 nm on the back, a length and width of about 1 cm, and a thickness of 5-50 microns was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. 0.001～0.02mol/L, 0.001～0.02mol/L and 0.003～0.06mol/L triethanolamine (0.015～0.3mol/L) of bismuth sulfate, copper sulfate and selenite and disodium edetate The mixed solution of salt (0.0035～0.07mol/L) and water is used as the electrolyte, and the copper-doped bismuth selenide is deposited under the conditions of two different deposition behaviors for 0.5-5 hours, and the current density of the two stages is 1× 10 ^-6 ～9×10 ^-6 A/mm ² and 1×10 ^-5 ～9×10 ^-5 A/mm ² (T ₁ : T ₂ =1:1～4:1, where T ₁ is from 1 to consists of 6 current pulses). During the deposition process, the electrolyte should be stirred at a constant speed.

Example 1. Preparation of Bamboo-shaped Bismuth Selenide Nanostructure Arrays by Template-Assisted Electrochemical Deposition

A 50nm-thick gold film on the back, an alumina template with a length and width of about 1 cm, and a thickness of 30 microns was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. L, 0.02mol/L and 0.06mol/L bismuth sulfate, copper sulfate and selenite triethanolamine (0.3mol/L) and edetate disodium salt (0.07mol/L) mixed with water As the electrolyte, two stages of different deposition behaviors are designed to deposit bismuth selenide or copper-doped bismuth selenide, and the current densities of the two stages are 9×10 ^-6 A/mm ² and 9×10 ^-5 A/mm 2 respectively mm ² (T ₁ :T ₂ =2:1, where T ₁ consists of 2 current pulses). Stir the electrolyte at a constant speed during the 1.5-hour deposition process. After the electrochemical deposition is completed, a layer of bismuth selenide or copper-doped bismuth selenide is evenly filled inside the alumina template, with a thickness of about 10 microns (see Figure 2). The outer diameter of the bamboo-shaped structure array is 50nm, and the aspect ratio for 200. It can be seen from the figure that bamboo-shaped copper-doped bismuth selenide nanostructure arrays are uniformly filled inside the channels of the alumina template.

Example 2. Preparation of Bamboo-shaped Bismuth Selenide Nanostructure Arrays by Template-Assisted Electrochemical Deposition

A 50nm-thick gold film on the back, an alumina template with a length and width of about 1 cm, and a thickness of 30 microns was used as the working electrode, the platinum sheet was used as the counter electrode, and the saturated calomel electrode was used as the reference electrode. L, 0.001mol/L and 0.003mol/L of bismuth sulfate, copper sulfate and triethanolamine (0.015mol/L) of selenite and EDTA disodium salt (0.0035mol/L) mixed with water As the electrolyte, two stages of different deposition behaviors are designed to deposit bismuth selenide or copper-doped bismuth selenide, and the current densities of the two stages are 1×10 ^-6 A/mm ² and 1×10 ^-5 A/mm 2 respectively mm ² (T ₁ :T ₂ =1:1, where T ₁ consists of 6 current pulses). Stir the electrolyte at a constant speed during the 5-hour deposition process. After the electrochemical deposition is completed, a layer of bismuth selenide or copper-doped bismuth selenide is evenly filled inside the alumina template, with a thickness of about 10 microns (see Figure 3). The outer diameter of the bamboo-shaped structure array is 50nm, and the aspect ratio for 200. It can be seen from Figure 3 that bamboo-shaped copper-doped bismuth selenide nanostructure arrays are uniformly filled inside the alumina template pores.

Finally, it should be noted that the purpose of the disclosed embodiments is to help further understand the present invention, but those skilled in the art can understand that various replacements and modifications can be made without departing from the spirit and scope of the present invention and the appended claims. It is possible. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the protection scope of the present invention is subject to the scope defined in the claims.

Claims (10)

1. a topological insulator material, is characterized in that, this material is bismuth selenide nanostructure and array thereof, and wherein, bismuth selenide nanostructure is bamboo-shaped, and its array is made of bamboo-shaped bismuth selenide with uniform size composed of nanostructures. 2. The topological insulator material according to claim 1, wherein the bismuth selenide nanostructure is doped with copper. 3. The topological insulator material according to claim 1, wherein the thickness of the bamboo-shaped bismuth selenide nanostructure array is 0.5-50 μm. 4. The topological insulator material as claimed in claim 1, wherein the outer diameter of the bamboo-shaped bismuth selenide nanostructure is 20-200nm, and the aspect ratio of the nanostructure is 2.5-2500. 5. the preparation method of bamboo-shaped bismuth selenide nanostructure array as claimed in claim 1, concrete steps comprise: 1) Preparation of electrolyte: the solute is bismuth sulfate, copper sulfate and selenous acid, and the solvent is a mixed solution of triethanolamine and disodium edetate and water; 2) Electrochemical device: the gold-plated template on the back is used as the working electrode, the anode is a platinum electrode, and the reference electrode is a saturated calomel electrode; 3) Deposition strategy: using a multi-step current pulse deposition method, filling bismuth selenide and copper-doped bismuth selenide alternating structures inside the template pores; 4) The template is removed to obtain a bamboo-shaped bismuth selenide nanostructure array. 6. the method for claim 5 is characterized in that, the concentration of bismuth sulfate, copper sulfate and selenous acid is respectively 0.001～0.02mol/L, 0.001～0.02mol/L and 0.003～0.06mol/L, three The ratio of ethanolamine: disodium edetate is 0.015-0.3mol/L: 0.0035-0.07mol/L. 7. The method according to claim 5, wherein the template is a nanoscale ordered porous template such as AAO or PC. 8 . The method according to claim 5 , wherein the multi-step current pulse deposition method comprises two deposition processes I ₁ =1×10 ^-6 ~ 9×10 ^-6 A/mm ² and I ₂ = 1×10 ^-5 to 9×10 ^-5 A/mm ² , T ₁ : T ₂ =1:1 to 4:1 in the two-stage deposition process, and the deposition time is 0.5 to 5 hours. 9. The method according to claim 8, characterized in that T ₁ consists of 1 to 6 current pulses. 10. The method according to claim 5, characterized in that, the bamboo-shaped bismuth selenide nanostructure array prepared by said method is annealed, and the specific annealing temperature is regulated by the following heating and constant temperature stages: 1) The starting temperature of the heating stage is selected from any temperature between 10°C and 25°C, and the termination temperature is selected from any temperature between 300-600°C; the heating rate in the heating stage is 1- 20℃/min; 2) The termination temperature is the temperature of the constant temperature stage, and the time of the constant temperature stage is 0.5-10 hours.

Images