Isotactic chromium atom cluster and self-assembly method and application thereof

Abstract

The invention discloses an identical chromium atom cluster as well as a self-assembly method and application thereof. The self-assembly method comprises the following steps: preparing a CrxNbSe2 single crystal; a single crystal is fixed to a sample support, a ceramic rod is fixed to the surface of the side, away from the sample support, of the single crystal, an assembled sample is placed in an ultrahigh vacuum cavity, the ceramic rod is impacted through external force so as to achieve sample cleavage, then the cleavage sample is transferred into a scanning tunneling microscope cavity in situ, and the sample is obtained. And cooling and surface morphology characterization are carried out. According to the method, the self-assembly of the large-area chromium atom clusters is successfully realized by utilizing a single crystal cleavage technology, the clusters are consistent in size and uniform in distribution and have extremely high chemical and structural stability, the sample size can reach the centimeter magnitude, and a foundation is laid for the application of the magnetic atom clusters on a new generation of semiconductor devices.

Description

Technical Field

[0001] The present invention relates to the field of single crystal technology, and more specifically to an isotropic chromium atom cluster and a self-assembly method and application thereof. Background Art

[0002] As an important intermediate state between single atoms and bulk materials, atomic clusters have shown great potential in basic scientific research and cutting-edge technology applications due to their unique quantum effects and size dependence. Among them, magnetic atomic clusters can achieve precise magnetic property regulation by regulating the size, composition and structure of clusters due to their ultra-high specific surface area and significant surface effects, which makes them have broad application prospects in spin electronics, catalysis, energy and biomedicine. Especially in the field of spin electronics, magnetic atomic clusters are considered to be ideal candidate materials for the next generation of spin electronic devices and single-molecule magnets due to their ultra-high magnetic storage density. In addition, magnetic atomic clusters also show potential quantum bit characteristics and can be used for information storage and processing in quantum computing. In addition, in catalytic applications, magnetic clusters such as iron and cobalt also show excellent performance in key catalytic processes such as oxygen reduction reaction and hydrogen evolution. In addition, in environmental protection, the efficient adsorption and degradation ability of magnetic clusters on pollutants has also attracted much attention.

[0003] However, although magnetic atomic clusters have shown great application potential, their development still faces many challenges. The stability of clusters is an important issue that limits their practical application. Due to their small size and high surface energy, clusters are prone to oxidation, agglomeration or dissolution, which affects their performance. Current magnetic atomic cluster preparation technologies, including gas-phase cluster condensation, laser evaporation, solution chemistry and atomic beam deposition, still have bottlenecks in achieving high stability, large-scale production and selective growth of single structures, which seriously restricts their application potential in semiconductor devices.

[0004] Therefore, developing a new method to prepare high-quality, large-area and highly stable magnetic atomic clusters has become the key to solving this problem. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide an isotropic chromium atomic cluster and its self-assembly method and application for efficiently preparing large-area isotropic chromium atomic clusters. By using single crystal cleavage technology, the self-assembly of large-area chromium atomic clusters is successfully realized. The clusters are of uniform size and uniform distribution, with extremely high chemical and structural stability. The sample size can reach the centimeter level, laying a foundation for the application of magnetic atomic clusters in a new generation of semiconductor devices.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for self-assembly of isotropic chromium atom clusters comprises the following steps:

[0008] (1) Cr, Nb and Se are weighed and mixed according to a stoichiometric ratio of x:1:2 to obtain a mixture, wherein x is 14% to 33%;

[0009] (2) pressing the mixture into a disc shape, then sealing it in a quartz tube, and preheating it at 950° C. to 1050° C. for 22 h to 26 h to obtain a pretreated precursor;

[0010] (3) The pretreated precursor and iodine are sealed in a quartz tube again, and placed in a horizontal furnace, and crystal growth is performed using a standard chemical vapor transport method. The temperatures of the hot end and the cold end of the horizontal furnace are 1040°C to 1060°C and 990°C to 1010°C, respectively, and the growth time is greater than 7 days. CrxNbSe is obtained at the cold end. 2 Single crystal;

[0011] (4) The Cr x NbSe 2 The single crystal is fixed to the sample holder, and the ceramic rod is fixed to the Cr x NbSe 2 on a surface of the single crystal away from the sample holder to obtain an assembled sample;

[0012] (5) placing the assembled sample in an ultra-high vacuum chamber and impacting the ceramic rod with an external force to achieve sample cleavage, then transferring the cleaved sample in situ to a scanning tunneling microscope chamber and cooling it to 77K to complete the self-assembly of identical chromium atomic clusters.

[0013] Optionally, in step (4), the fixation is performed using EPO-TEK H20E silver glue; the fixation comprises the following steps:

[0014] Weigh part A and part B of EPO-TEK H20E silver colloid, mix them in a mass ratio of (0.9-1.1):1 (the mass ratio is preferably 1:1), stir evenly and place for 15-20 minutes, preferably 20 minutes;

[0015] Use the prepared silver glue to x NbSe 2 The single crystal is adhered to the sample holder, dried at 110°C to 130°C for 25min to 30min, preferably at 120°C for 30min, and then the ceramic rod is bonded to the Cr using the prepared silver glue. x NbSe 2The single crystal is placed on a surface of a side away from the sample holder and dried at a temperature of 110° C. to 130° C. for 25 min to 30 min, preferably at a temperature of 120° C. for 30 min.

[0016] Optionally, in step (5), the ultra-high vacuum conditions in the ultra-high vacuum chamber and the scanning tunneling microscope chamber are 5×10 -10 mbar~1x10 -9 mbar.

[0017] Optionally, in step (4), the sample holder is made of stainless steel.

[0018] Optionally, the sample holder and the ceramic rod are respectively cleaned with anhydrous ethanol, specifically comprising: placing the sample holder and the ceramic rod in anhydrous ethanol for ultrasonic cleaning for 15 minutes, taking them out with tweezers after cleaning, and gently wiping them with dust-free paper to remove residual ethanol on the surface.

[0019] Optionally, the diameter of the isochromium atomic cluster is 0.76 nm and the height is And the cluster coverage is similar to Cr x NbSe 2 The single crystals have a consistent chromium doping level.

[0020] Optionally, in step (5), the tool for striking the ceramic rod may be a rocking bar or other tool suitable for striking operations.

[0021] Optionally, in step (5), an external force impacts the ceramic rod in a direction perpendicular to the ceramic rod to achieve sample cleavage.

[0022] The invention also discloses an isotropic chromium atomic cluster obtained by the self-assembly method of the isotropic chromium atomic clusters.

[0023] The present invention also discloses an isotropic chromium atomic cluster obtained by the self-assembly method of the isotropic chromium atomic cluster, or the application of the isotropic chromium atomic cluster in a new generation of semiconductor devices.

[0024] Implementing the embodiments of the present invention will have the following beneficial effects:

[0025] (1) The self-assembly method of isotropic chromium atomic clusters provided by the present invention is to perform chromium-doped NbSe under ultra-high vacuum conditions. 2 By performing in-situ cleavage on the single crystal, large-area orderly arranged identical chromium atomic clusters were successfully prepared. The atomic clusters were spontaneously formed after cleavage under ultra-high vacuum and their distribution was highly orderly, which effectively avoided the interference of impurities and obtained extremely high-purity chromium atomic clusters.

[0026] (2) After being placed in a vacuum environment for several hours, the chromium atomic clusters obtained by the self-assembly method of the isotropic chromium atomic clusters provided by the present invention remain stable in morphology, showing extremely high structural stability, which is suitable for subsequent device processing and is conducive to the application of magnetic clusters in new generation semiconductor devices.

[0027] (3) The single crystal cleavage method used in the present invention can be used to cleave Cr doped with different chromium. x NbSe 2 Single crystals are prepared to obtain chromium atomic clusters with different coverages; at the same time, the coverage and area size of the chromium atomic clusters prepared by the present invention can be controlled by the chromium doping amount and the size of the single crystal sample.

[0028] (4) The self-assembly method of isotropic chromium atomic clusters provided by the present invention has the advantage of realizing large-area self-assembly of magnetic atomic clusters. The sample can reach the centimeter level, providing an ideal material for the development of a new generation of semiconductor devices. It is expected to be applied to information storage, transmission and processing, and will play an important role in the post-Moore era.

[0029] In summary, the present invention realizes for the first time the preparation of large-area isotropic chromium atomic clusters by single crystal cleavage technology, and the in-situ cleavage of chromium-doped NbSe 2 Single crystal, using scanning tunneling microscopy, observed that a large area of ​​orderly arranged identical chromium atomic clusters were formed on the surface of the single crystal, each cluster had a diameter of 0.76nm and a height of The number and density of clusters can be controlled by the amount of chromium doping, and after long-term placement, the crystal structure and size remain stable, suitable for subsequent device processing and application. The present invention overcomes the problems of the prior art in terms of large-scale production of atomic clusters, selective growth of a single structure, and high stability control, expands new preparation processes, lays a solid foundation for the application of magnetic atomic clusters in new generation semiconductor devices, provides a new experimental platform for studying cutting-edge scientific issues such as quantum materials and spin electronics, and opens up new possibilities for the development of high-performance, low-power functional devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the self-assembly of chromium atomic clusters in Example 1 of the present invention.

[0031] Figure 2 Cr of Test Example 1 of the present invention 0.14 NbSe 2 Scanning tunneling microscopy (STM) image of chromium atomic clusters on the surface of a single crystal.

[0032] Figure 3 Cr of Test Example 1 of the present invention 0.14 NbSe 2 3D image of chromium atomic clusters on the surface of a single crystal.

[0033] Figure 4 Cr of Test Example 1 of the present invention 0.14 NbSe 2 Size calibration of chromium atomic clusters on single crystal surfaces.

[0034] Figure 5 Cr of Test Example 2 of the present invention 0.14 NbSe 2 Transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) scanning images of a single crystal.

[0035] Figure 6 Cr in the embodiment of the present invention 0.14 NbSe 2 Schematic diagram of single crystal size and cluster formation. The single crystal size is ~5 mm.

[0036] Figure 7 Cr of Test Example 1 of the present invention 0.14 NbSe 2 and Cr 0.33 NbSe 2 STM image of chromium atomic clusters on the single crystal surface.

[0037] Figure 8 Cr in Example 1 of the present invention 0.14 NbSe 2 STM image of chromium atomic clusters on the single crystal surface.

[0038] Fig. 9 Cr in Example 1 of the present invention 0.14 NbSe 2 Angle-resolved photoemission spectroscopy (ARPES) image of a single crystal. DETAILED DESCRIPTION

[0039] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0040] Example 1

[0041] The self-assembly method of the isotropic chromium atomic clusters of this embodiment comprises the following steps:

[0042] (1) Cr, Nb and Se were weighed and mixed according to a stoichiometric ratio of 0.14:1:2, and the mixture was pressed into a disc shape, which was then sealed in a quartz tube and preheated at 1000° C. for 24 h to obtain a pretreated precursor.

[0043] (2) The pretreated precursor and iodine are sealed in a quartz tube again and placed in a horizontal furnace. A standard chemical vapor transport method is used to grow crystals. The temperatures of the hot end and the cold end of the horizontal furnace are 1050°C and 1000°C, respectively. The growth time is greater than 7 days. Cr is obtained at the cold end. 0.14 NbSe 2 Single crystal.

[0044] (3) Weigh part A and part B of EPO-TEK H20E silver colloid, mix them in a mass ratio of 1:1, stir evenly and let stand for 20 minutes.

[0045] (4) After the sample holder and the ceramic rod were ultrasonically cleaned with anhydrous ethanol, the silver glue obtained in step (3) was used to coat the Cr 0.14 NbSe 2 The single crystal was adhered to the sample holder and placed on a heating table to dry at 120°C for 30 min. Then, the ceramic rod was bonded to the Cr using the silver glue obtained in step (3). 0.14 NbSe 2 The single crystal was placed on one side of the sample holder and dried under the same conditions.

[0046] (5) The processed samples were transferred to an ultra-high vacuum chamber and the ultra-high vacuum conditions were 5x10 -10 In the sample processing chamber of mbar, the sample is cleaved by hitting the ceramic rod in a direction perpendicular to the ceramic rod (such as Figure 1 After cleavage, the sample was immediately placed in ultra-high vacuum at 5x10 -10 mbar in a scanning tunneling microscope chamber and cooled to 77K. 0.14 NbSe 2 In single crystals, chromium atoms spontaneously form large-area atomic clusters on the surface.

[0047] Example 2

[0048] The only difference between this embodiment and embodiment 1 is that the chromium doping amount is 33%.

[0049] Test Example 1

[0050] Scanning tunneling microscope test

[0051] The chromium atom clusters obtained in Example 1 and Example 2 were measured using a low-temperature scanning tunneling microscope (LT-STM) produced by German ScientaOmicron Company, and the test temperature range was 4.5K to 77K. The morphology of the clusters can be measured by scanning tunneling microscopy. The STM images in different scanning ranges show that Cr 0.14 NbSe 2The chromium clusters obtained after single crystal cleavage are of uniform size and evenly distributed on the entire cleavage surface, such as Figure 2 and Figure 3 As shown. The size of the sample cleavage surface determines the size of the atomic cluster array. The size of the cleaved single crystal is ~5mm ( Figure 6 Left), which means that the size of the chromium atom cluster array prepared by single crystal cleavage technology is also ~5mm. STM can accurately measure the size of the cluster, the height is The diameter is 0.76nm ( Figure 4 ). STM can also measure the coverage of clusters. Cr 0.14 NbSe 2 Single crystal and Cr 0.33 NbSe 2 The chromium clusters formed on the single crystal surface accounted for 14.16% and 36.78%, respectively, which is consistent with the chromium doping amount ( Figure 7 ). This shows that the coverage of chromium clusters increases with the increase of chromium doping amount. After being placed in a vacuum environment for 1 hour, the morphology of chromium atom clusters remains stable, showing extremely high structural stability ( Figure 8 ).

[0052] Test Example 2

[0053] Scanning transmission microscopy test

[0054] The Cr used in Example 1 0.14 NbSe 2 The single crystal was tested by TEM. The test instrument was a 120KV field emission transmission electron microscope produced by JEOL Ltd., model JEM-1400FLASH, with a line resolution of 0.20nm and an acceleration voltage of 20-200KV. The TEM measurement results showed that the chromium atoms were not in the NbSe 2 The interlayer position is located at the niobium atomic layer position ( Figure 5 After single crystal cleavage, chromium atoms move from the niobium atomic layer to the sample surface ( Figure 6 right).

[0055] Test Example 3

[0056] Angle-resolved photoelectron spectroscopy

[0057] The Cr used in Example 1 0.14 NbSe 2 The single crystal was tested by ARPES. The test instrument was an angle-resolved photoelectron spectrometer produced by ScientaOmicron of Germany. The analyzer model was DA30L, with an energy resolution of 150 meV and an angle resolution of 0.1°. The ARPES measurement results showed that the intrinsic NbSe2 In comparison, Cr 0.14 NbSe 2 The energy band structure of the sample shifts downward as a whole, which indicates that the Cr x NbSe 2 The electron doping of single crystal samples was achieved ( Fig. 9 ).

[0058] Example 3

[0059] The self-assembly method of the isotropic chromium atomic clusters of this embodiment comprises the following steps:

[0060] (1) Cr, Nb and Se were weighed and mixed according to a stoichiometric ratio of 0.20:1:2, and the mixture was pressed into a disc shape, then sealed in a quartz tube, and preheated at 1050° C. for 22 h to obtain a pretreated precursor.

[0061] (2) The pretreated precursor and iodine are sealed in a quartz tube again, and placed in a horizontal furnace, and crystal growth is performed using a standard chemical vapor transport method. The temperatures of the hot end and the cold end of the horizontal furnace are 1040°C and 990°C, respectively, and the growth time is greater than 7 days. Cr is obtained at the cold end. 0.20 NbSe 2 Single crystal.

[0062] (3) Weigh part A and part B of EPO-TEK H20E silver colloid, mix them in a mass ratio of 1:1, stir evenly and let stand for 20 minutes.

[0063] (4) After the sample holder and the ceramic rod were ultrasonically cleaned with anhydrous ethanol, the silver glue obtained in step (3) was used to coat the Cr 0.20 NbSe 2 The single crystal was adhered to the sample holder and placed on a heating table to dry at 120°C for 30 min. Then, the ceramic rod was bonded to the Cr using the silver glue obtained in step (3). 0.20 NbSe 2 The single crystal was placed on one side of the sample holder and dried under the same conditions.

[0064] (5) The processed samples were transferred to an ultra-high vacuum chamber and the ultra-high vacuum conditions were 5x10 -10 mbar sample processing chamber, the sample is cleaved by hitting the ceramic rod in a direction perpendicular to the ceramic rod through the rocking rod. After cleavage, the sample is immediately transferred to the ultra-high vacuum condition of 5x10 -10 mbar in a scanning tunneling microscope chamber and cooled to 77K. 0.20 NbSe 2 In single crystals, chromium atoms spontaneously form large-area atomic clusters on the surface.

[0065] The effect of this embodiment is the same as that of embodiment 1.

[0066] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for self-assembly of isotropic chromium atom clusters, characterized in that: The following steps are involved: (1) Cr, Nb and Se are weighed and mixed according to a stoichiometric ratio of x:1:2 to obtain a mixture, wherein x is 14% to 33%; (2) pressing the mixture into a disc shape, then sealing it in a quartz tube, and preheating it at 950° C. to 1050° C. for 22 h to 26 h to obtain a pretreated precursor; (3) The pretreated precursor and iodine are sealed in a quartz tube again, and placed in a horizontal furnace, and crystal growth is performed using a standard chemical vapor transport method. The temperatures of the hot end and the cold end of the horizontal furnace are 1040° C. to 1060° C. and 990° C. to 1010° C., respectively, and the growth time is greater than 7 days. Cr is obtained at the cold end. x NbSe2 single crystal; (4) The Cr x The NbSe2 single crystal is fixed on the sample holder, and the ceramic rod is fixed on the Cr x On the surface of the NbSe2 single crystal away from the sample holder, an assembled sample is obtained; (5) placing the assembled sample in an ultra-high vacuum chamber and impacting the ceramic rod with an external force to achieve sample cleavage, then transferring the cleaved sample in situ to a scanning tunneling microscope chamber and cooling it to 77K, and observing the self-assembly of identical chromium atomic clusters using a scanning tunneling microscope.

2. The self-assembly method of isotropic chromium atom clusters according to claim 1, characterized in that: In step (4), the fixation is carried out using EPO-TEK H20E silver glue; the fixation comprises the following steps: Weigh part A and part B of EPO-TEK H20E silver colloid, mix them in a mass ratio of (0.9-1.1):1, stir evenly and place for 15-20 minutes; Use the prepared silver glue to x The NbSe2 single crystal is adhered to the sample holder and dried at 110°C to 130°C for 25min to 30min. Then, the ceramic rod is bonded to the Cr x The NbSe2 single crystal is placed on the surface of the side away from the sample holder and dried at a temperature of 110° C. to 130° C. for 25 min to 30 min.

3. The self-assembly method of isotropic chromium atom clusters according to claim 1, characterized in that: In step (5), the ultra-high vacuum conditions in the ultra-high vacuum cavity and the scanning tunneling microscope cavity are 5×10 -10 mbar~1ⅹ10 - 9 mbar.

4. The self-assembly method of isotactic chromium atom clusters according to claim 1, characterized in that: In step (4), the sample holder is made of stainless steel.

5. The self-assembly method of isotactic chromium atom clusters according to claim 1, characterized in that: The sample holder and the ceramic rod are respectively the sample holder and the ceramic rod cleaned with anhydrous ethanol.

6. The self-assembly method of isotactic chromium atom clusters according to claim 1, characterized in that: The diameter of the isochromium atomic cluster is 0.76 nm and the height is And the cluster coverage is similar to Cr x The chromium doping amount of NbSe2 single crystal is consistent.

7. The self-assembly method of isotactic chromium atom clusters according to claim 1, characterized in that: In step (5), an external force impacts the ceramic rod in a direction perpendicular to the ceramic rod to achieve sample cleavage.

8. An isotactic chromium atomic cluster obtained by the self-assembly method of isotactic chromium atomic clusters as claimed in any one of claims 1 to 7.

9. An isotropic chromium atomic cluster obtained by the self-assembly method of isotropic chromium atomic clusters as claimed in any one of claims 1 to 7, or an application of the isotropic chromium atomic clusters as claimed in claim 8 in a new generation semiconductor device.

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