CN114232102B - Two-dimensional ZnTe crystal material and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the field of optical encryption materials, and particularly discloses a two-dimensional ZnTe crystal material as well as a preparation method and application thereof, wherein the preparation method comprises the following steps: respectively taking zinc chloride and tellurium powder as a Zn source and a Te source, respectively placing the Zn source and the Te source at the upstream of a central temperature zone, respectively placing molecular sieves above the Zn source and the Te source, and placing a substrate at the downstream of the central temperature zone; controlling the temperature of the central temperature zone to 850-980 ℃, carrying the evaporated Zn source and Te source to the substrate by using carrier gas containing hydrogen, and reacting the Zn source and the Te source under the action of the hydrogen to generate a flaky two-dimensional ZnTe crystal material on the substrate. The method can prepare the two-dimensional ZnTe crystal material with regular appearance and uniform element distribution, and realizes the synthesis of the ultrathin ZnTe nanosheet.

Description

A kind of two-dimensional ZnTe crystal material and its preparation method and application

technical field

The invention belongs to the field of optical encryption materials, and more specifically relates to a two-dimensional ZnTe crystal material and its preparation method and application.

Background technique

With the rapid development of information technology, information security has aroused people's close attention. Encryption, as a means of ensuring information security, is extremely important in data storage and transmission (ACS Nano 2021, 15, 6257-6265). However, most of the current encryption methods focus on terminal encryption, and rarely involve internal logic operation encryption (Angew. Chem. Int. Ed. 2019, 58, 15128-15135). As a basic computing unit, logical operations generate a large amount of data, and are vulnerable to hacking and tampering. Therefore, the encryption of logical operations is crucial to further improve information security.

In general, Photoluminescence (PL) is one of the most commonly used encryption methods due to its fast readability and simple design. In recent years, many photoluminescent materials such as quantum dots, upconversion nanoparticles, perovskites, and organic dyes have been used for information encryption (Nano Lett. 2021, 21, 5186-5194). However, the PL properties of these materials are usually not tunable after preparation. To implement encryption, a more complex design is required to tune the PL properties, which is not conducive to applying logic to operate encryption. Moreover, since the invisibility of PL under natural light has been widely understood, the encryption of optical information can be easily broken. To sum up, there is an urgent need for an advanced encryption method with multi-modality, high adjustability, and high security.

ZnTe is a direct bandgap semiconductor with a bandgap of 2.26eV. Many stoichiometric defects are easily generated during the synthesis of ZnTe, which induces the formation of defect emission peaks, making ZnTe exhibit rich emission modes (Adv. Mater. 2016, 28, 276-283). In addition, the optical properties of ZnTe can be easily adjusted by an external field, which makes it promising to realize a highly secure logic operation encryption process in ZnTe (J. Electron. Mater. 2004, 33, 579-582). Therefore, ZnTe has obvious advantages in logic operation encryption. However, the current synthesis of ZnTe is still limited to nanowires, and there are still many limitations in the synthesis of ultrathin ZnTe nanosheets.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a two-dimensional ZnTe crystal material and its preparation method and application. The purpose is to prepare a two-dimensional ZnTe crystal material with regular shape and uniform element distribution.

In order to achieve the above object, according to the first aspect of the present invention, a kind of preparation method of two-dimensional ZnTe crystal material is proposed, comprising the steps:

Zinc chloride and tellurium powders were used as Zn source and Te source respectively, Zn source and Te source were placed upstream of the central temperature zone, and molecular sieves were placed above the Zn source and Te source, and the substrate was placed downstream of the central temperature zone ; Control the temperature of the central temperature zone at 850°C to 980°C, and bring the evaporated Zn source and Te source to the substrate through the carrier gas containing hydrogen, and the Zn source and Te source react under the action of hydrogen to form a sheet on the substrate Two-dimensional ZnTe crystal material.

As a further preference, the flow rate of the hydrogen is 5 sccm-10 sccm.

As a further preference, the reaction time is 10 minutes to 20 minutes.

As a further preference, the Zn source is farther away from the central temperature zone than the Te source.

As a further preference, the Zn source and the Te source are respectively placed 16 cm and 14 cm upstream from the central temperature zone, and the substrate is placed 10 cm downstream from the central temperature zone.

As a further preference, the temperature rise rate in the central temperature zone is 30° C./min˜40° C./min.

As a further preference, the carrier gas is a mixture of argon and hydrogen, and the flow rate of argon is 50 sccm.

As a further preference, the reaction is carried out in a horizontal tube furnace with a single temperature zone, the outer diameter of the nozzle is 25 mm, and the length of the central temperature zone is 10 cm; the substrate is a fluorphlogopite sheet.

According to the second aspect of the present invention, a two-dimensional ZnTe crystal material is provided, which is prepared by the above method.

According to the third aspect of the present invention, an application of a two-dimensional ZnTe crystal material is provided, and the above-mentioned two-dimensional ZnTe crystal material is used for optical encryption.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

1, the present invention selects zinc chloride and tellurium powder as source, and adopts molecular sieve, can slow down the evaporation rate of zinc chloride and tellurium powder, zinc _chloride and tellurium powder react under the action of H to generate ZnTe and HCl gas, The melting point of zinc chloride is low, which reduces the reaction temperature, reduces energy consumption, and realizes the controllability of the preparation process; at the same time, the temperature in the central temperature zone is controlled, thereby obtaining a two-dimensional ZnTe crystal material with regular shape and uniform element distribution , achieved the synthesis of ultrathin ZnTe nanosheets with a thickness of about 7nm.

2. The present invention comprehensively controls the temperature in the temperature zone of the control center and the flow rate of the carrier gas. On the one hand, if the reaction temperature is too low, there will be too few ZnTe nanosheet products. The evaporation content is less, thereby reducing the yield; on the other hand, the high reaction temperature will cause the source evaporation rate to be too fast, resulting in a lot of granular samples and making the substrate dirty. At the same time, argon is used as the transport gas, and hydrogen is used as the reaction gas to ensure that an appropriate amount of Zn source and Te source reach the substrate, and at the same time, there is a sufficient amount of reaction gas to fully react, and hydrogen has the effect of etching and thinning, thus obtaining Ultrathin flake ZnTe.

3. The present invention maintains a certain distance between the substrate and the central temperature zone, which can prevent the substrate from being damaged due to excessive temperature; at the same time, according to the melting points of the Zn source and the Te source, the Zn source and the Te source are respectively placed in the central temperature zone At different positions upstream of the ZnTe crystal material, the Zn source and the Te source can be guaranteed to reach the substrate evenly, so that the element distribution in the ZnTe crystal material is more uniform.

Description of drawings

Fig. 1 is a schematic diagram of a device for preparing a two-dimensional ZnTe crystal material according to an embodiment of the present invention;

Figures 2a to 2c are top views of the morphology of the two-dimensional ZnTe crystal material prepared in Examples 1-3 of the present invention;

Fig. 3 is the measurement characterization diagram of the thickness of the two-dimensional ZnTe crystal material prepared in Example 1 of the present invention;

Fig. 4a and Fig. 4b are analysis diagrams of zinc and tellurium elemental components of the two-dimensional ZnTe crystal material prepared in Example 1 of the present invention, respectively.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

A method for preparing a two-dimensional ZnTe crystal material provided in an embodiment of the present invention includes the following steps:

A horizontal tube furnace with a single temperature zone is used, as shown in Figure 1, the outer diameter of the nozzle is 25 mm, and the vacuum is evacuated to about 10 Pa before the reaction, and then filled with 600 sccm Ar to atmospheric pressure, and repeatedly scrubbed to remove residual oxygen;

Zinc chloride and tellurium powders (purity>99.99%) were used as Zn source and Te source respectively, Zn source and Te source were placed upstream of the central temperature zone, and molecular sieves were placed above Zn source and Te source, and fluorine gold was used The mica sheet is used as the deposition substrate and placed downstream of the central temperature zone;

The central temperature zone, that is, the constant temperature zone, is 10cm in length, and the temperature in the central temperature zone is raised to 850°C to 980°C at a heating rate of 30°C/min to 40°C/min; then the Zn source and the Te source are brought to the React at the substrate, and the pressure is maintained at one atmosphere. The Zn source and the Te source react under the action of hydrogen to generate ZnTe and HCl gas. The reaction time is 10 minutes to 20 minutes. After the reaction, the carrier gas remains unchanged. Two-dimensional ZnTe crystal material obtained on fluorphlogopite sheet.

Further, since the melting point of the Zn source is lower than that of the Te source, the Zn source is farther away from the central temperature zone. Specifically, the Zn source and the Te source are placed 16 cm and 14 cm upstream from the central temperature zone, and the substrate is placed at a distance from the central temperature zone. 10cm downstream of the temperature zone to avoid damage to the substrate.

Further, the carrier gas is a mixed gas of Ar and H ₂ , wherein Ar is used as a transport gas, H ₂ is used as a reaction gas, and the flow rate of Ar is 50 sccm, and the flow rate of H ₂ is 5 sccm-10 sccm.

The following are specific examples:

Example 1

A horizontal tube furnace with a single temperature zone is used, with a tube length of 90 cm, an outer diameter of 25 mm, a tube wall thickness of 2 mm, a constant temperature zone of 10 cm, a central temperature of 950 °C, and a heating rate of 30 °C/min. Zinc chloride and tellurium powder (purity>99.99%) were used as Zn and Te sources, and molecular sieves were placed above the sources, respectively, at 14 cm and 16 cm upstream from the central temperature zone; fluorine phlogopite sheets were used as deposition substrates 10cm downstream from the central temperature zone; before the reaction, pre-vacuumize to about 10Pa, then fill it with 600sccm Ar to atmospheric pressure, and repeatedly wash the gas to eliminate residual oxygen; pass 50sccm Ar and 5sccm H during the reaction ₂ as a carrier gas, and the pressure was maintained at one atmosphere, and the reaction time was 15 minutes. After the reaction, the carrier gas remained unchanged, and the product was cooled to room temperature with the furnace, and a two-dimensional ZnTe crystal material was obtained from a fluorophlogopite sheet.

As shown in Figure 2a, it is the morphology characterization of the obtained two-dimensional ZnTe crystal material; as shown in Figure 3, it is the measurement of the thickness of the two-dimensional ZnTe crystal material, the thickness is about 6.4nm, confirming that the obtained product is a two-dimensional material . As shown in Figure 4a and Figure 4b, it is the element composition analysis of the two-dimensional ZnTe crystal material. From the element mapping diagram of the product, it can be seen that the two elements of zinc and tellurium are evenly distributed, and the product is a ZnTe crystal material.

Example 2

A horizontal tube furnace with a single temperature zone is used, with a tube length of 90 cm, an outer diameter of 25 mm, a tube wall thickness of 2 mm, a constant temperature zone of 10 cm, a central temperature of 850 °C, and a heating rate of 30 °C/min. Zinc chloride and tellurium powder (purity>99.99%) were used as Zn and Te sources, and molecular sieves were placed above the sources, respectively, at 14 cm and 16 cm upstream from the central temperature zone; fluorine phlogopite sheets were used as deposition substrates 10cm downstream from the central temperature zone; before the reaction, pre-vacuumize to about 10Pa, then fill with 600sccm Ar to atmospheric pressure, and repeatedly wash the gas to eliminate residual oxygen; pass 50sccm Ar and 6sccm H during the reaction ₂ as a carrier gas, and the pressure is maintained at an atmospheric pressure. The reaction time is 15 minutes. After the reaction, the carrier gas remains unchanged. The product is cooled to room temperature with the furnace, and a two-dimensional ZnTe crystal material is obtained from a fluorophlogopite sheet. Its morphology is shown in the figure 2b.

Example 3

A horizontal tube furnace with a single temperature zone is used, with a tube length of 90cm, an outer diameter of 25mm, a tube wall thickness of 2mm, a constant temperature zone of 10cm, a central temperature of 980°C, and a heating rate of 40°C/min. Zinc chloride and tellurium powder (purity>99.99%) were used as Zn and Te sources, and molecular sieves were placed above the sources, respectively, at 14 cm and 16 cm upstream from the central temperature zone; fluorine phlogopite sheets were used as deposition substrates 10cm downstream from the central temperature zone; before the reaction, pre-vacuumize to about 10Pa, then fill with 600sccm Ar to atmospheric pressure, and repeatedly wash the gas to eliminate residual oxygen; pass 50sccm Ar and 8sccm H during the reaction ₂ as a carrier gas, and the pressure is maintained at an atmospheric pressure. The reaction time is 15 minutes. After the reaction, the carrier gas remains unchanged. The product is cooled to room temperature with the furnace, and a two-dimensional ZnTe crystal material is obtained from a fluorophlogopite sheet. Its morphology is shown in the figure 2c shown.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (9)

1. a preparation method of two-dimensional ZnTe crystal material, is characterized in that, comprises the steps: Zinc chloride and tellurium powders were used as Zn source and Te source respectively, Zn source and Te source were placed upstream of the central temperature zone, and molecular sieves were placed above the Zn source and Te source, and the substrate was placed downstream of the central temperature zone ; Control the temperature of the central temperature zone at 850°C to 980°C, bring the evaporated Zn source and Te source to the substrate through the carrier gas containing hydrogen, the flow rate of hydrogen is 5sccm to 10sccm, and the Zn source and Te source react under the action of hydrogen , generate a sheet-like two-dimensional ZnTe crystal material on the substrate. 2 . The method for preparing the two-dimensional ZnTe crystal material according to claim 1 , wherein the reaction time is 10 min˜20 min. 3. The preparation method of the two-dimensional ZnTe crystal material as claimed in claim 1, characterized in that, compared with the Te source, the distance between the Zn source and the central temperature zone is farther. 4. the preparation method of two-dimensional ZnTe crystal material as claimed in claim 3 is characterized in that, Zn source and Te source are respectively placed in the upstream place apart from central temperature zone 16cm, 14cm, and substrate is placed in apart from central temperature zone 10cm downstream of. 5 . The preparation method of two-dimensional ZnTe crystal material according to claim 1 , characterized in that, the heating rate in the central temperature zone is 30° C./min˜40° C./min. 6 . The method for preparing a two-dimensional ZnTe crystal material according to claim 1 , wherein the carrier gas is a mixture of argon and hydrogen, and the flow rate of argon is 50 sccm. 7. as the preparation method of the two-dimensional ZnTe crystal material described in any one of claim 1-6, it is characterized in that, reaction is carried out in single-temperature zone horizontal tube furnace, 25mm of nozzle external diameters, and wherein central temperature zone length is 10 cm; the substrate is a fluorine phlogopite sheet. 8. A two-dimensional ZnTe crystal material, characterized in that it is prepared by the method according to any one of claims 1-7. 9. An application of the two-dimensional ZnTe crystal material as claimed in claim 8, characterized in that the two-dimensional ZnTe crystal material is used for optical encryption.

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