A method for preparing high-quality two-dimensional nickel selenium nanometer islands by using a molecular beam epitaxy growth technology, high-quality two-dimensional nickel selenium nanometer islands and applications
By using molecular beam epitaxy to grow two-dimensional nickel selenide nanoislands under ultra-high vacuum conditions, the problems of high energy consumption and difficult control in existing technologies have been solved, and high-quality nanoislands have been prepared, providing an excellent material basis for next-generation semiconductor devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2026-05-21
- Publication Date
- 2026-06-16
AI Technical Summary
Existing methods for preparing two-dimensional nickel selenide nanoislands suffer from problems such as high energy consumption, high cost, difficulty in accurately controlling the size and density of nanoislands, and unstable crystal quality, which limit their application in high-performance devices.
Using molecular beam epitaxy under ultra-high vacuum conditions, with strontium titanate single crystal as the substrate and nickel and selenium sources as evaporation sources, high-quality two-dimensional nickel selenium nanoislands are grown on the substrate through electron beam evaporation and thermal evaporation. By controlling the temperature and vacuum environment, the precise nucleation and growth of the nanoislands are achieved.
Two-dimensional nickel selenide nanoislands with highly controllable coverage and high crystallinity were prepared, which are suitable for next-generation semiconductor devices, especially infrared photodetectors, and improve the uniformity and crystallinity of the nanoislands.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor materials technology, and more specifically, to a method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy, the high-quality two-dimensional nickel-selenium nanoislands, and their applications. Background Technology
[0002] Two-dimensional materials, due to their unique electronic structure and excellent physicochemical properties, have broad application prospects in catalysis, electronic devices, and energy storage. Among them, transition metal chalcogenides (TMDs) and their analogues (such as nickel selenides) have attracted much attention from researchers due to their tunable interlayer interactions, high specific surface area, and good conductivity. Among numerous two-dimensional selenium materials, two-dimensional nickel selenide nanoislands exhibit excellent performance in applications such as electrocatalytic hydrogen evolution, oxygen evolution, and supercapacitors due to their quantum size effect and significant edge effect. However, existing methods for preparing two-dimensional nickel selenide nanoislands still have limitations.
[0003] Traditional physical vapor deposition (PVD) methods often require high temperatures and vacuum conditions, resulting in high energy consumption, high cost, and difficulty in precisely controlling the size and density of nanoislands. While chemical vapor deposition (CVD) methods can achieve large-area growth, they are highly demanding in terms of precursor volatility, reaction temperature windows, and substrate selection, easily leading to problems such as uneven nanoisland size distribution and unstable crystal quality. Furthermore, two-dimensional nickel-selenium nanoislands prepared by solution methods typically suffer from low crystallinity, numerous surface defects, and difficulty in precisely controlling layer thickness, limiting their application in high-performance devices. The two-dimensional nanoisland structure itself places even more stringent requirements on controllable fabrication. Unlike traditional bulk materials and continuous thin films, two-dimensional nanoislands require precise and coordinated control over two-dimensional nucleation, lateral dimensions, thickness (height), density, and surface coverage. Compared to PVD, CVD, and solution methods, molecular beam epitaxy (MBE) has advantages such as ultra-high vacuum, low damage, atomic-level deposition rate, and in-situ controllable growth process. It can achieve precise nucleation and growth of nanoislands under mild conditions, significantly improve product uniformity and crystal quality, and effectively solve the shortcomings of traditional methods in large-area uniform preparation and precise control of atomic-level thickness. It provides a reliable technical path for the controllable preparation of high-performance two-dimensional nickel selenide nanoislands.
[0004] Therefore, developing a simple, controllable, low-cost method for preparing two-dimensional nickel selenide nanoislands with high quality remains a pressing technical problem to be solved in this field.
[0005] Nickel-selenium nanoislands are two-dimensional structures whose core properties stem from quantum confinement effects and significant surface / boundary effects. Compared to metallic or semi-metallic bulk materials and thin films, nanoislands possess novel magnetism induced by edge states and extremely high surface chemical activity, making them a promising fundamental material platform for quantum devices, nanophotonics, spintronics, and efficient catalysis. To date, no studies have been reported on the fabrication of two-dimensional nickel-selenium nanoislands using molecular beam epitaxy. Summary of the Invention
[0006] The purpose of this invention is to overcome the aforementioned deficiencies in the existing technology and provide a method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy (MBE), along with the high-quality two-dimensional nickel-selenium nanoislands and their applications. This invention achieves the preparation of high-quality two-dimensional nickel-selenium nanoislands for the first time. The method uses strontium titanate single crystal as a substrate, and degassing and high-temperature annealing are performed on the substrate under ultra-high vacuum conditions until regular steps are formed on its surface. Subsequently, nickel and selenium sources are used as evaporation sources. In the MBE cavity, the nickel source is provided by electron beam evaporation, and the selenium source is provided by thermal evaporation. Combining the ultra-high vacuum environment and precise temperature control, high-quality two-dimensional nickel-selenium nanoislands are successfully prepared on the pretreated substrate using MBE, providing an excellent material basis for the development of next-generation semiconductor devices.
[0007] To achieve the above objectives, the technical solution of the present invention is as follows:
[0008] A method for preparing high-quality two-dimensional nickel selenide nanoislands using molecular beam epitaxy includes the following steps: (1) Under ultra-high vacuum conditions, the strontium titanate substrate is pretreated so that the surface morphology of the pretreated substrate is a regular step, and the width of the step is 50nm~200nm; (2) Using nickel and selenium sources as evaporation sources, nickel selenium nanoislands are grown on the pretreated substrate using molecular beam epitaxy. During the growth process, the electron beam evaporation current of the nickel source is 2.25A and the electron beam current intensity of the nickel source is 30 nA; the evaporation temperature of the selenium source is 150℃; the temperature of the pretreated substrate is maintained at 400℃; the growth rate is 0.009 layers / min and the growth time is 60 min; the height of the nickel selenium nanoisland is 10Å~20Å and the lateral dimension is 10nm~80nm.
[0009] Optionally, in step (2), the nickel source is provided by electron beam evaporation within the molecular beam epitaxy cavity; the selenium source is provided by thermal evaporation.
[0010] Optionally, in step (2), the heating rate of the pretreated substrate and the selenium source is 15℃ / min; the current increase rate of the nickel source is 0.45A / min.
[0011] Optionally, in step (2), the vacuum is maintained at 1×10⁻⁶ during the growth process. -9 mbar.
[0012] Optionally, in step (2), the nickel source beam current during the growth process is 29 min / layer, and the selenium source beam current is 7.1 min / layer.
[0013] Optionally, in step (1), the pretreatment includes: cleaning the strontium titanate substrate and then placing it into the sample holder, transmitting it into the molecular beam epitaxy cavity, and performing the pretreatment at 5×10⁻⁶ ppm. -10 Under ultra-high vacuum conditions of mbar, the strontium titanate substrate was heated to 400°C, held at that temperature for 2 hours, and then degassed. After that, the substrate was heated to 1000°C and held at that temperature for 0.5 hours.
[0014] Optionally, in step (1), the strontium titanate substrate is a SrTiO3(001) wafer.
[0015] Optionally, in step (1), the cleaning includes: placing the strontium titanate substrate in anhydrous ethanol, ultrasonically cleaning for 15 minutes, and after cleaning, removing it with tweezers and gently wiping away excess ethanol with lint-free paper.
[0016] The present invention also discloses a method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described above.
[0017] This invention also discloses the application of high-quality two-dimensional nickel-selenium nanoislands prepared by the method described above using molecular beam epitaxy for next-generation semiconductor devices.
[0018] Optionally, the next-generation semiconductor device is an infrared photodetector.
[0019] Implementing the embodiments of the present invention will have the following beneficial effects: (1) The preparation method provided by the present invention uses strontium titanate single crystal as substrate and nickel source and selenium source as reaction materials. For the first time, molecular beam epitaxy growth technology is used in combination with ultra-high vacuum environment and precise temperature control to successfully prepare high-quality two-dimensional nickel selenium nanoislands.
[0020] (2) The present invention grows nano-islands uniformly distributed on the substrate surface by molecular beam epitaxy equipment. The height of the nickel selenide nano-islands is 10 Å to 20 Å and the lateral size ranges from 10 nm to 80 nm. In a region of 500 nm × 500 nm, the coverage of the nano-islands reaches 50% to 53%, realizing the controllable growth of high-quality nano-islands.
[0021] (3) The present invention controls the entire growth process to be carried out under ultra-high vacuum, and the element materials used are of extremely high purity, which can effectively avoid interference from impurities and obtain high-purity nano islands.
[0022] (4) The preparation method of the present invention has the advantages of precise control and high product quality, providing ideal nano-island materials for the development of next-generation semiconductor devices. It is expected to be applied in the fields of information storage, transmission and processing, and play an important role in the post-Moore era.
[0023] In summary, this invention successfully fabricated high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy (MBE) technology by selecting a strontium titanate single-crystal substrate, employing nickel and selenium as evaporation sources, and optimizing substrate pretreatment and growth conditions. The nickel-selenium nanoislands have a height of 10 Å to 20 Å and a lateral size ranging from 10 nm to 80 nm. Within a 500 nm × 500 nm region, the nanoisland coverage reaches 50% to 53%. Scanning tunneling spectroscopy results show that the bandgap of the nickel-selenium nanoislands is 0.67 eV to 1.1 eV, indicating promising applications in infrared photodetectors. Compared with existing fabrication techniques, this invention overcomes the problems of large-area fabrication and highly precise control of nanoislands, expanding the fabrication process for novel nanoislands. The method of this invention possesses advantages such as high controllability, adjustable coverage, and high crystal quality, demonstrating significant advantages in the precise fabrication of semiconductor nanoislands and providing an excellent core material foundation for the development of next-generation semiconductor devices. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of a method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy (MBE) in an embodiment of the present invention.
[0025] Figure 2 This is an overall structural diagram of the nickel-selenium nanoisland of Embodiment 1 of the present invention.
[0026] Figure 3 This is a microstructure diagram of the nickel-selenium nanoisland of Example 1 of the present invention.
[0027] Figure 4 for Figure 3 Size diagram of the nickel-selenium nanoisland corresponding to a in the microstructure diagram.
[0028] Figure 5 for Figure 3 Size diagram of the nickel-selenium nanoisland corresponding to b in the microstructure diagram.
[0029] Figure 6 This is a statistical chart showing the coverage of nickel-selenium nanoislands in Example 1 of the present invention.
[0030] Figure 7 This is the scanning tunneling microscopy spectrum of the nickel-selenium nanoislands in Example 1 of the present invention.
[0031] Figure 8 This is a graph showing the STM measurement results of Comparative Example 1 of the present invention.
[0032] Figure 9 This is a diagram showing the scanning tunneling spectrum test results of Comparative Example 1 of the present invention.
[0033] Figure 10 The image shows the STM measurement results of Comparative Example 2 of this invention at a growth time of 30 min.
[0034] Figure 11 The image shows the scanning tunneling spectrum test results of Comparative Example 2 of the present invention at a growth time of 30 min.
[0035] Figure 12 The image shows the STM measurement results of Comparative Example 3 of this invention at a selenium source evaporation temperature of 130°C.
[0036] Figure 13 The image shows the STM measurement results of Comparative Example 4 of this invention at a substrate temperature of 360°C.
[0037] Figure 14 The image shows the STM measurement results of Comparative Example 4 of this invention at a substrate temperature of 420°C. Detailed Implementation
[0038] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.
[0039] Example 1 like Figure 1 As shown, the method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy in this embodiment includes the following steps: (1) Place the SrTiO3(001) wafer in anhydrous ethanol and ultrasonically clean it for 15 minutes. After cleaning, remove it with tweezers and gently wipe away excess ethanol with lint-free paper. Then, load the cleaned SrTiO3(001) wafer into the sample holder and transfer it into the molecular beam epitaxy cavity at 5 × 10⁻⁶. -10 Under ultra-high vacuum conditions of mbar, the strontium titanate substrate was heated to 400℃, held for 2 hours and then degassed. After that, the substrate was heated to 1000℃ and held for 0.5 hours, so that the surface morphology of the substrate exhibited a regular step structure with a step width of 50nm~200nm.
[0040] (2) Nickel-selenium nanoislands were grown on the pretreated substrate using molecular beam epitaxy with nickel and selenium sources as evaporation sources. The growth process parameters were controlled as follows: the vacuum was maintained at 1×10 during the growth process. -9mbar, the selenium source is provided by thermal evaporation, and the selenium source is heated to the target evaporation temperature of 150℃ at a heating rate of 15℃ / min; the nickel source is provided by electron beam evaporation, and the current is increased to the target current of 2.25A at a rate of 0.45A / min, with an electron beam current intensity of 30 nA; the temperature of the pretreated substrate is heated to 400℃ at a heating rate of 15℃ / min and held; the nickel source beam current during the growth process is 29 min / layer, and the selenium source beam current is 7.1 min / layer; the growth rate is 0.009 layers / min, and the growth time is 60 min.
[0041] Test Example 1: Scanning Tunneling Microscopy Test The two-dimensional nickel selenium nanoislands prepared in Example 1 were characterized using a low-temperature scanning tunneling microscope (LT-STM) manufactured by Scienta Omicron GmbH, Germany, with a test temperature range of 4K to 300K.
[0042] Test results are as follows Figures 2-7 As shown: Figures 2-3 The morphological characteristics of the nano islands are clearly presented, indicating that the controllable growth of high-quality nickel selenium nano islands can be achieved by precisely controlling the process parameters. Figures 4-5 The results show that the height of the nickel selenium nanoislands is 10 Å to 20 Å, and the lateral size ranges from 10 nm to 80 nm. Figure 6 Statistical results show that within a 500nm×500nm region, the coverage of nanoislands reaches 50%~53%; Figure 7 The scanning tunneling spectroscopy test results show that the bandgap of the nickel selenium nanoislands is 1.111 eV.
[0043] Comparative Example 1 The only difference between this comparative example and Example 1 is that the evaporation current of the nickel source in step (2) is adjusted to 2.3A, and the electron beam intensity of the nickel source is adjusted to 73.5nA. Figures 8-9 It can be seen that the nickel / selenium ratio has a significant regulatory effect on the morphology of the sample during the growth process: when the selenium / nickel ratio decreases, it is easier to form fractal islands. However, the fractal islands are uneven in size, irregular in shape, and have poor crystallinity, which is not conducive to efficient carrier transport and stable control of device performance, and makes it difficult to meet the application requirements of high-performance semiconductor devices.
[0044] Comparative Example 2 The only difference between this comparative example and Example 1 is that the growth time of the nickel selenium nanoislands in step (2) is adjusted to 30 min. Figures 10-11 As shown, the two-dimensional nickel selenium nanoislands have a uniform size distribution and cover the substrate surface, with a height of 6 Å to 12 Å and a lateral size ranging from 10 nm to 40 nm. Their crystallinity is slightly inferior. Figures 10-11The results show that although the two-dimensional nickel selenide nanoislands prepared in this comparative example have a relatively uniform size distribution and cover the substrate surface, their crystal quality is slightly poor. Scanning tunneling spectroscopy tests show that their bandgap is only 0.67 eV, which is significantly lower than 1.111 eV in Example 1. However, the material defect density is higher and the carrier transport characteristics are worse, which is not conducive to achieving the high-efficiency photoelectric response and stable electrical performance required for high-performance semiconductor devices.
[0045] Comparative Example 3 The only difference between this comparative example and Example 1 is that the evaporation temperature of the selenium source was set to 130°C. The corresponding STM test results are as follows: Figure 12 As shown, the poor crystal quality resulted in the formation of many non-crystalline substances, rather than regular-shaped two-dimensional nickel-selenium islands. This imbalance in the stoichiometry of the sample, caused by insufficient supply of non-metallic elements, leads to decreased crystal quality and increased defects, which not only deteriorates the morphology but also significantly reduces the electrical and optical performance of the device.
[0046] Comparative Example 4 The only difference between this comparative example and Example 1 is that the temperature of the pretreated substrate was set to 360°C and 420°C, respectively. When the substrate temperature was set to 360°C, the corresponding STM test results are as follows: Figure 13 As shown, due to insufficient surface mobility of deposited atoms, random nucleation and disordered aggregation occur, resulting in a large number of irregular, discrete three-dimensional island-like morphologies of varying sizes. When the substrate temperature is set to 420℃, the corresponding STM test results are as follows... Figure 14 As shown, intense atomic diffusion and severe island fusion result in a rough and disordered surface morphology, making STM scanning prone to scratching and image blurring. This demonstrates that excessively high or low substrate temperatures reduce sample crystal quality and morphological uniformity, ultimately leading to device performance degradation.
[0047] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.
Claims
1. A method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy, characterized in that, Includes the following steps: (1) Under ultra-high vacuum conditions, the strontium titanate substrate is pretreated so that the surface morphology of the pretreated substrate is a regular step, and the width of the step is 50nm~200nm; (2) Using nickel and selenium sources as evaporation sources, nickel selenium nanoislands are grown on the pretreated substrate using molecular beam epitaxy. During the growth process, the electron beam evaporation current of the nickel source is 2.25A and the electron beam current intensity of the nickel source is 30nA; the evaporation temperature of the selenium source is 150℃; the temperature of the pretreated substrate is maintained at 400℃; the growth rate is 0.009 layers / min and the growth time is 60min; the height of the nickel selenium nanoisland is 10Å~20Å and the lateral dimension is 10nm~80nm.
2. The method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in claim 1, characterized in that, In step (2), the nickel source is provided by electron beam evaporation within the molecular beam epitaxy cavity; the selenium source is provided by thermal evaporation.
3. The method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in claim 1, characterized in that, In step (2), the heating rate of the pretreated substrate and the selenium source is 15℃ / min; the current increase rate of the nickel source is 0.45A / min.
4. The method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in claim 1, characterized in that, In step (2), the vacuum was maintained at 1 x 10 -9 mbar during growth.
5. The method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in claim 1, characterized in that, In step (2), the nickel source beam current during the growth process is 29 min / layer, and the selenium source beam current is 7.1 min / layer.
6. The method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in claim 1, characterized in that, In step (1), the pretreatment comprises: cleaning the strontium titanate substrate and loading it into a sample holder and transferring it into a molecular beam epitaxy chamber, under an ultra-high vacuum condition of 5x10 -10 mbar, heating the strontium titanate substrate to 400℃, keeping it for 2h, degassing, and then heating the substrate to 1000℃, keeping it for 0.5h.
7. The method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in claim 6, characterized in that, In step (1), the strontium titanate substrate is a SrTiO3(001) wafer.
8. The method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in claim 6, characterized in that, In step (1), the cleaning includes: placing the strontium titanate substrate in anhydrous ethanol, ultrasonically cleaning for 15 minutes, and after cleaning, removing it with tweezers and gently wiping away excess ethanol with lint-free paper.
9. A method for preparing high-quality two-dimensional nickel-selenium nanoislands using molecular beam epitaxy as described in any one of claims 1-8.
10. The application of high-quality two-dimensional nickel selenide nanoislands prepared by the method for preparing high-quality two-dimensional nickel selenide nanoislands using molecular beam epitaxy as described in any one of claims 1-8 in next-generation semiconductor devices.