Method and system for observing boundary and defect of two-dimensional material single crystal, electronic equipment and storage medium
By using visible light dark field microscope to identify defects in the single crystal region of two-dimensional material, the problem of poor performance of two-dimensional devices is solved, and fast and low-cost characterization and improvement are achieved.
Patent Information
- Application Number
- CN202411272186.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2024-12-13
AI Technical Summary
The prior art is difficult to quickly and at low cost to characterize the cracks and single crystal fusion boundaries inside single crystals of artificial two-dimensional materials, resulting in poor performance of two-dimensional devices.
A visible light dark field microscope is used to observe the two-dimensional material layer. By screening the closed area surrounded by continuous highlights in the optical image, it can identify whether there are defects in the single crystal region, such as cracks or single crystal fusion boundaries, to achieve fast and low-cost characterization.
Effectively identify and avoid defects in two-dimensional materials, improve the performance of two-dimensional devices, and dark field microscopy technology has advantages in equipment complexity and cost.
Smart Images
Figure CN119125179A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of two-dimensional material characterization, and in particular to a method and system, electronic equipment, and storage medium for observing boundaries and defects of single crystals of two-dimensional materials. Background Art
[0002] Two-dimensional materials have important application prospects in the field of advanced electronic devices. At present, due to the limitation that artificially synthesized two-dimensional materials cannot reach the level of large-sized single crystals, in the preparation process of two-dimensional materials, it is usually necessary to control the growth of seed crystals to inhibit the fusion of different single crystals into polycrystals.
[0003] However, since the location and time of nucleation during the growth of two-dimensional materials are random, fusion of different single crystals may still occur. In addition, as the size of the single crystal increases, the probability of cracks is also increasing. The degree of damage to the single crystal leads to poor performance of the subsequent two-dimensional devices.
[0004] Therefore, how to quickly and cost-effectively characterize the cracks and single crystal fusion boundaries inside artificial two-dimensional material single crystals, and then use reliable single crystal areas to improve the performance of two-dimensional devices, is an urgent problem that needs to be solved. Summary of the invention
[0005] Based on this, the embodiments of the present application provide a method and system, electronic device, and storage medium for observing the boundaries and defects of single crystals of two-dimensional materials, which can quickly and cost-effectively characterize the cracks and single crystal fusion boundaries inside artificial two-dimensional material single crystals, and then use reliable single crystal areas to improve the performance of two-dimensional devices.
[0006] According to some embodiments, the present application provides a method for observing boundaries and defects of a two-dimensional material single crystal, comprising the following steps:
[0007] Providing a sample, the sample comprising a substrate and a two-dimensional material layer located on the substrate;
[0008] Observe the sample using a dark field microscope to obtain an optical image of the sample;
[0009] Screening a closed area surrounded by continuous bright spots in the optical image, and extracting an area in the closed area that meets a preset area threshold as a single crystal area;
[0010] If there are continuous bright spots in the single crystal region, then there are defects in the single crystal region in the two-dimensional material layer.
[0011] In the disclosed embodiment, a visible light dark field microscope is used to observe the two-dimensional material layer located on the substrate, the substrate is imaged as a black background, and the position where the height changes dramatically on the two-dimensional material layer is imaged as a bright color (i.e., a bright spot). In this way, the closed area surrounded by continuous bright spots is first determined to be a single crystal area, and then whether there are continuous bright spots in the single crystal area is observed. In this way, by observing whether there are continuous bright spots in the single crystal area, it is possible to quickly obtain whether there are positions where the height changes dramatically in the single crystal area, that is, to quickly identify whether there are defects in the single crystal area (such as cracks or single crystal fusion boundaries). In addition, visible light dark field microscopy technology has very large advantages in low equipment complexity, low cost, and instantaneous imaging. Therefore, the disclosed embodiment can quickly and at low cost characterize the cracks and single crystal fusion boundaries inside the artificial two-dimensional material single crystal, and then by avoiding and using reliable single crystal areas, improve the performance of two-dimensional devices.
[0012] According to some embodiments, if there are continuous bright spots in the single crystal region whose light intensity is less than that at the boundary of the single crystal region, then there are boundary fusions of multiple single crystal regions in the two-dimensional material layer.
[0013] According to some embodiments, observing a sample using a dark field microscope to obtain an optical image of the sample includes the following steps:
[0014] The light source provides visible light as incident light;
[0015] The incident light is incident on the sample at an oblique angle from outside the objective lens in a dark field microscope, and the incident light irradiating the sample is Rayleigh scattered;
[0016] The scattered light is collected by an optical information receiving device in a dark field microscope, and converted into an optical photograph by an imaging device in the dark field microscope.
[0017] According to some embodiments, the light source also provides red light as incident light.
[0018] In the disclosed embodiments, a device using a red light source can be used to observe two-dimensional samples with photoresist or other photosensitive materials, and is suitable for a wider range of semiconductor synthesis, processing, integrated circuit design, manufacturing and other scenarios.
[0019] According to some embodiments, the closed area is in the shape of a regular pattern.
[0020] According to some embodiments, the substrate comprises a flat substrate; and the dark field microscope comprises an epi-dark field microscope.
[0021] According to some embodiments, the present disclosure provides an electronic device, comprising: a memory, a processor, and a display. The memory is used to store a computer program. The processor is used to run the computer program to implement the method for observing the boundaries and defects of a two-dimensional material single crystal as described in the above embodiments. The display is used to output the processing results of the processor.
[0022] In the embodiments of the present disclosure, the technical effects that can be achieved by the electronic device are the same as the technical effects that can be achieved by the method for observing the boundaries and defects of single crystals of two-dimensional materials in the aforementioned embodiments, and will not be described in detail here.
[0023] According to some embodiments, the present disclosure provides a storage medium storing program instructions. When the program instructions are executed, the method for observing the boundaries and defects of a two-dimensional material single crystal as described in the above embodiments is implemented.
[0024] In the embodiments of the present disclosure, the technical effects that can be achieved by the storage medium are the same as the technical effects that can be achieved by the method for observing the boundaries and defects of two-dimensional material single crystals in the aforementioned embodiments, and will not be described in detail here.
[0025] According to some embodiments, the present disclosure provides a system for observing defects in single crystals of two-dimensional materials, comprising: a graphics algorithm module, an integrated circuit layout design module, and a dark field microscope. The graphics algorithm module is configured to analyze and process optical photos of the dark field microscope and screen out defect-free single crystal regions; the integrated circuit layout design module is configured to design two-dimensional devices and integrated circuits based on defect-free single crystal regions.
[0026] In the disclosed embodiment, the artificially synthesized two-dimensional material sample can be based on the optical photograph obtained by the dark field microscope, and the graphic algorithm module can be used to instantly generate the boundary of the two-dimensional material thin layer and screen out the single crystal area that can be used to process the two-dimensional device with consistent performance. The above image can be further programmed to instantly generate a format suitable for the integrated circuit layout design module, and design the two-dimensional device and integrated circuit based on the screened available area.
[0027] According to some embodiments, the present disclosure provides, on the other hand, a system for observing defects in a two-dimensional material single crystal, comprising: a two-dimensional material preparation device and a dark field microscope embedded in the two-dimensional material preparation device.
[0028] In the disclosed embodiment, a dark field microscope is embedded in the two-dimensional material preparation device, which can dynamically observe the processes of two-dimensional crystal nucleation, growth, fusion, etc. in real time, thus providing direct experimental data and theoretical analysis basis for the boundary between crystal growth and single crystal fusion formation for basic research in two-dimensional crystallography. In this way, the experimental data can further guide the controllable growth and synthesis of high-quality, large-area, single-crystalline two-dimensional materials. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 A schematic flow chart of a method for observing boundaries and defects of a two-dimensional material single crystal provided in some embodiments;
[0030] Figure 2A schematic flow chart of step S300 in a method for observing boundaries and defects of a two-dimensional material single crystal provided in some embodiments;
[0031] Figure 3 A schematic diagram of a cross-sectional structure of a structure obtained in S100 in a method for observing boundaries and defects of a two-dimensional material single crystal provided in some embodiments;
[0032] Figure 4 A schematic structural diagram of S200 in a method for observing boundaries and defects of a two-dimensional material single crystal provided in some embodiments;
[0033] FIG5(a) is an optical photograph of a dark field microscope of molybdenum disulfide provided in some embodiments when illuminated by a white light source; FIG5(b) is an optical photograph of a dark field microscope of molybdenum disulfide provided in some embodiments when illuminated by a red light source;
[0034] Figure 6 Another optical photograph of dark field microscope of molybdenum disulfide provided in some embodiments when illuminated by white light source;
[0035] Figure 7 This is another optical photograph of a dark field microscope of molybdenum disulfide provided in some embodiments when illuminated by a white light source;
[0036] FIG8(a) is another dark-field microscope optical photograph of molybdenum disulfide provided in some embodiments when illuminated by a white light source; FIG8(b) is an enlarged view of the single crystal fusion region in FIG8(a). FIG8(c) is an optical photograph of molybdenum disulfide provided in some embodiments when illuminated by a white light source under a bright-field microscope;
[0037] FIG. 9( a ) is a graph showing a gate voltage-drain current relationship of a MoS2 field effect transistor provided in some embodiments; FIG. 9( b ) is a graph showing a gate voltage-drain current relationship of another MoS2 field effect transistor provided in some embodiments;
[0038] Figure 10(a) is another dark field microscope optical photograph of molybdenum disulfide provided in some embodiments when illuminated by a red light source; Figure 10(b) is an enlarged view of the single crystal fusion area in Figure 10(a). Figure 10(c) is a schematic diagram of the process from growth to fusion of two molybdenum disulfide single crystals provided in some embodiments.
[0039] Description of reference numerals:
[0040] 1. Sample; 11. Substrate; 12. Two-dimensional material layer; 2. Light source; 3. Optical information receiving device; 31. Objective lens; 32. Focusing lens group; 4. Imaging device; 5. Collimating lens group; 6. Reflector. DETAILED DESCRIPTION
[0041] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.
[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.
[0043] In the case of using “including”, “having”, and “comprising” described herein, another component may be added unless a clear limiting term such as “only”, “consisting of”, etc. is used. Unless mentioned otherwise, a term in the singular form may include a plural form and should not be understood as being one in number.
[0044] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.
[0045] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.
[0046] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.
[0047] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.
[0048] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.
[0049] Embodiments of the invention are described herein with reference to schematic diagrams that are ideal embodiments (and intermediate structures) of the present invention, and variations in the shapes shown due to, for example, manufacturing techniques and / or tolerances are to be expected. Therefore, embodiments of the present invention should not be limited to the specific shapes of regions shown herein, but rather include deviations in shapes due to, for example, manufacturing techniques.
[0050] Two-dimensional materials, especially two-dimensional semiconductor materials, are an important option for the development of advanced devices, especially advanced electronic devices. Among them, in the semiconductor integrated circuit industry, which is regarded as the most promising industry, the use of two-dimensional semiconductor materials to process field effect transistor channels is an important option for realizing advanced structural processes such as nanosheets and ring gates. To realize the practical application of two-dimensional devices, two-dimensional materials cannot rely on peeling natural crystals. They can only be grown through artificial synthesis (such as chemical vapor deposition process), and artificially synthesized two-dimensional materials cannot currently reach the ultra-high single crystal level of three-dimensional bulk semiconductor materials represented by silicon. Therefore, artificially synthesized two-dimensional materials often lead to low performance consistency of two-dimensional devices, which cannot meet the requirements of further integration.
[0051] Two-dimensional materials have important application prospects in the field of advanced electronic devices. At present, due to the limitation that artificially synthesized two-dimensional materials cannot reach the level of large-size single crystals, in order to produce two-dimensional devices with high processability and reliable batch processing consistency, two-dimensional materials usually control the growth degree of seed crystals and inhibit the fusion of different single crystals into polycrystals. But even so, since the position and time of nucleation during the growth of two-dimensional materials are random, fusion of different single crystals may still occur. In addition, as the area of single crystals increases, the probability of cracks is also increasing, which leads to poor performance of subsequent two-dimensional devices (including low performance consistency).
[0052] In order to avoid the above problems, it is necessary to characterize the artificial two-dimensional materials used before processing the device to identify cracks and single crystal fusion boundaries that cause potential risks. The characterization technology needs to be non-destructive to the two-dimensional material itself, fast, efficient and low-cost, and easy to embed into existing semiconductor synthesis and processing equipment. The current technologies that can characterize cracks and single crystal fusion boundaries of artificial two-dimensional materials, such as Raman imaging and scanning electron microscopy, do not meet the above requirements.
[0053] Therefore, how to quickly and cost-effectively characterize the cracks inside single crystals of artificial two-dimensional materials and the single crystal fusion boundaries, and thereby improve the performance of two-dimensional devices, is an urgent problem that needs to be solved.
[0054] Based on this, the embodiments of the present application provide a method and system, electronic device, and storage medium for observing the boundaries and defects of two-dimensional material single crystals, which can quickly and cost-effectively characterize the interior of artificial two-dimensional material single crystals and the single crystal fusion boundaries, thereby improving the performance of two-dimensional devices.
[0055] See also Figure 1 Some embodiments of the present application provide a method for observing boundaries and defects of a two-dimensional material single crystal, including steps S100 to S400.
[0056] S100, providing a sample, where the sample includes a substrate and a two-dimensional material layer located on the substrate.
[0057] S200, observe the sample using a dark field microscope to obtain an optical image of the sample.
[0058] S300, screening the closed area surrounded by continuous bright spots in the optical image, and extracting the area in the closed area that meets a preset area threshold as a single crystal area.
[0059] S400: If there are continuous bright spots in the single crystal region, then there are defects in the single crystal region in the two-dimensional material layer.
[0060] In the disclosed embodiment, a dark-field microscope is used to observe the two-dimensional material layer located on the substrate, the substrate is imaged as a black background, and the position where the height changes dramatically on the two-dimensional material layer is imaged as a bright color (i.e., a bright spot). In this way, the closed area surrounded by continuous bright spots is first determined to be a single crystal area, and then whether there are continuous bright spots in the single crystal area is observed. In this way, by observing whether there are continuous bright spots in the single crystal area, it is possible to quickly obtain whether there are positions where the height changes dramatically in the single crystal area, that is, to quickly identify whether there are defects in the single crystal area (such as cracks or single crystal fusion boundaries). In addition, dark-field microscopy technology has very large advantages in low equipment complexity, low cost, and instantaneous imaging. Therefore, the disclosed embodiment can quickly and inexpensively characterize cracks and single crystal fusion boundaries inside artificial two-dimensional material single crystals, thereby improving the performance of two-dimensional devices.
[0061] In some embodiments, the substrate comprises a flat substrate; and the dark field microscope comprises an epi-illumination dark field microscope.
[0062] In some embodiments, the closed area is in the shape of a regular pattern.
[0063] In some embodiments, see Figure 2 Step S200 uses a dark field microscope to observe the sample, and obtaining an optical image of the sample includes steps S201 to S203.
[0064] S201, a light source provides visible light as incident light.
[0065] S202, incident light is incident on the sample at an oblique angle from outside the objective lens in the dark field microscope, and the incident light irradiated on the sample is Rayleigh scattered.
[0066] S203, using an optical information receiving device in a dark field microscope to collect the scattered light, and using an imaging device in the dark field microscope to convert it into an optical photograph.
[0067] In some embodiments, the light source may also provide red light as incident light.
[0068] Illustratively, the red light includes long wavelength red light.
[0069] In some embodiments, in step S400, if there are continuous bright spots in the single crystal region whose light intensity is less than that at the boundary of the single crystal region, then there are boundary fusions of multiple single crystal regions in the two-dimensional material layer.
[0070] It should be noted that, in the above-mentioned embodiments, the execution of each step in the method is not strictly limited in order, and these steps may not necessarily be executed in the order described, but may be executed in other ways. Moreover, at least a part of any step may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but may be executed at different times, and the execution order of these sub-steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps.
[0071] In order to more clearly illustrate the method for observing the boundaries and defects of a two-dimensional material single crystal provided by the above embodiment, Figure 3 to Figure 8(c) The method is described in detail.
[0072] In step S100, refer to Figure 3 , providing a sample 1, the sample 1 includes a substrate 11 and a two-dimensional material layer 12 located on the substrate 11.
[0073] In some embodiments, the substrate includes a flat substrate, such as a SiO 2 / Si wafer flat substrate, a sapphire flat substrate, etc.
[0074] In some examples, a 300nm SiO2 / Si wafer flat substrate is used as the substrate 11, and a single layer of molybdenum disulfide (MoS2) is used as the two-dimensional material layer 12 as an example, a chemical vapor deposition (CVD) process is used to form a single layer of molybdenum disulfide (MoS2) on the SiO2 / Si wafer flat substrate, and observation is performed.
[0075] For example, forming a single-layer MoS2 two-dimensional material layer on a flat SiO2 / Si wafer substrate includes the following steps: thoroughly cleaning a 300nm SiO2 / Si wafer, annealing it to make it flat, and growing a single-layer MoS2 two-dimensional material layer using a CVD process; cleaning the SiO2 / Si wafer with concentrated sulfuric acid / hydrogen peroxide (volume ratio of 3:1); cleaning the wafer with ammonia water, rinsing it with deionized water, and drying it with nitrogen; placing the cleaned wafer into a quartz tube furnace and annealing it in an oxygen atmosphere at 1000°C; loading pure sulfur (S) and molybdenum trioxide (MoO3) powder into a quartz tube furnace, heating it to 900°C in a flowing argon (Ar) atmosphere, and growing a MoS2 two-dimensional material layer.
[0076] In step S201, refer to Figure 4 , light source 2 provides visible light as incident light.
[0077] In some embodiments, within the visible light band, the light source 2 provides visible light with tunable wavelength (including white light).
[0078] In some embodiments, the light intensity of the visible light provided by the light source 2 is adjustable (including adjustable power or adjustable camera integration time).
[0079] In step S202, refer to Figure 4 , the incident light is incident on the sample 1 at an inclined angle from outside the objective lens 31 in the dark field microscope, and the incident light irradiated on the sample 1 undergoes Rayleigh scattering.
[0080] Here, the imaging principle is the Rayleigh scattering law, that is, the higher the flatness of the observation position, the weaker the scattering. Therefore, a flat substrate is imaged as a black background, and targets with drastic height changes, such as dust particles (precursor vapor deposition or environmental pollutants) and two-dimensional material boundaries, are imaged as bright colors. In theory, the target height change rate is positively correlated with the brightness.
[0081] In addition, the light source 2 is emitted from outside the objective lens 31 toward the sample 1 at an inclined angle, and the reflected light will not enter the objective lens / camera.
[0082] In step S203, refer to Figure 4 , the scattered light is collected by an optical information receiving device 3 in a dark field microscope, and converted into an optical photograph by an imaging device 4 in a dark field microscope.
[0083] In some embodiments, the dark field microscope comprises an epi-illumination dark field microscope.
[0084] For some examples, see Figure 4 The dark field microscope further comprises: a collimating lens group 5, a reflector 6 and a focusing lens group 32. The collimating lens group 5 is used to convert the visible light generated by the light source 2 into parallel light beams. The reflector 6 is used to change the directions of the parallel light beams. The focusing lens group 32 is used to direct the parallel light beams after changing their directions to the sample 1 at an inclined angle.
[0085] In other embodiments, the light source 2 may also provide red light as the incident light.
[0086] In the embodiments of the present disclosure, a device using a red light source (or other monochromatic visible light source with a longer wavelength) can be used to observe two-dimensional samples with photoresist or other photosensitive materials, and is suitable for a wider range of semiconductor synthesis, processing, integrated circuit design, manufacturing and other scenarios.
[0087] In some embodiments, under the condition that the structure of the epi-illumination dark-field microscope (microscope and camera) remains unchanged, the white light source can be replaced by a monochromatic light source (such as red light). According to the Rayleigh scattering law, the resolution of the dark-field microscopic image should be inversely proportional to the wavelength. Considering that the planar size of the thin layer of artificially synthesized two-dimensional materials is on the scale of tens or even hundreds of microns, the monochromatic visible light (red light) with the longest wavelength will theoretically reduce the image resolution, but it is still sufficient for the effective identification of the single crystal boundaries, cracks, and multi-seed single crystal fusion boundaries of the two-dimensional material, as shown in Figure 5 (a) and Figure 5 (b). Among them, Figure 5 (a) is a comparison of the dark-field microscopic imaging effect when illuminated by a white light source (the scale bar is 100μm); Figure 5 (b) is a comparison of the dark-field microscopic imaging effect when illuminated by a red light source (635nm) (the scale bar is 100μm).
[0088] For example, as shown in FIG5(b), the dark light edge can identify the single crystal region without damaging the two-dimensional material itself or any photosensitive materials such as photoresist that may exist, and then process devices (such as field effect transistors) based on the observed single crystal region, thereby achieving batch processing of two-dimensional devices with highly consistent electrical performance and reliable further circuit integration.
[0089] In step S300, refer to Figure 6 , screen the closed area surrounded by continuous bright spots in the optical image, and extract the area in the closed area that meets the preset area threshold as the single crystal area (i.e. Figure 6 The single crystal thin layer in Figure 6 This is an optical photograph taken using a dark-field microscope, taking a single-layer MoS2 two-dimensional material synthesized by CVD process as an example (the light source is white light, and the scale bar is 100μm).
[0090] For example, Figure 6 As shown, the MoS2 single crystal that has grown to a larger size appears as a regular triangular boundary outlined by a regular distribution of bright spots.
[0091] In some embodiments, since the pixel resolution of the camera is limited, objects smaller than a certain size will be imaged to the same pixel, resulting in accumulated brightness. Therefore, for artificially synthesized two-dimensional material samples, small-sized objects including but not limited to dust particles (condensation of synthetic precursor vapor and environmental pollutants), undergrown seed crystals (two-dimensional materials have no practical value if their area is too small) appear as irregularly distributed light spots (as shown in FIG. 5 ). Based on this, some non-useful objects can be identified and screened out (i.e., screened out). Figure 6 small target spot in the image).
[0092] Furthermore, in some embodiments, for useful targets (two-dimensional materials with a large area), the thickness is at the sub-nanometer atomic scale (for example, a single layer of MoS2, the thickness is about 0.65nm), and its edge will appear as a regular pattern edge contour surrounded by bright spots (i.e. Figure 6 Based on this, the image processing algorithm and program can be used to preliminarily screen out possible two-dimensional material targets, that is, to extract the area in the closed area that meets the preset area threshold as the single crystal area.
[0093] For example, the preset area threshold is greater than 200 μm 2 For example, the preset area threshold can be 200 μm 2 , 250μm 2 、300μm 2 、350μm 2 or 400μm 2 etc.
[0094] In step S400, refer to Figure 7 to Figure 8(c) If there are continuous bright spots in the single crystal region, then there are defects in the single crystal region in the two-dimensional material layer 12.
[0095] Here, defects in the single crystal region include two-dimensional crystal cracks and boundaries formed by the fusion of single crystal thin layers grown from different seed crystals.
[0096] In some embodiments, see Figure 7 , because the height change caused by the crack is consistent with the height change of the boundary of the two-dimensional material, there is a continuous bright spot in the single crystal region, and the light intensity of the continuous bright spot is roughly the same as the light intensity of the continuous bright spot at the boundary of the single crystal region, which means that there is a crack inside the single crystal region. Artificially synthesized two-dimensional materials will produce cracks when the area is large, and only continuous two-dimensional materials without cracks can be used. In this way, by observing whether there is a continuous bright spot inside the single crystal region with roughly the same light intensity as the continuous bright spot at the boundary of the single crystal region, it is possible to quickly identify whether there is a crack in the single crystal region.
[0097] For example, Figure 7 This is an optical photograph of a single-layer MoS2 two-dimensional material synthesized by CVD process using a dark field microscope (light source is white light, scale bar is 100μm). By observing the cracks inside the MoS2 single crystal, it can be seen that Figure 7 Theoretically, all the areas within the two triangles above can be used to process two-dimensional devices with the same performance. Figure 7 The triangular single crystal below is divided into two parts by the crack, and the processed two-dimensional device area cannot cross the crack.
[0098] In some other embodiments, see Figure 8(a) to Figure 8(c)If there are continuous bright spots in the single crystal region whose light intensity is less than the boundary of the single crystal region, then there are multiple single crystal regions in the two-dimensional material layer 12 that are fused at the boundaries.
[0099] Here, since artificially synthesized two-dimensional materials generally cannot guarantee single crystal growth, but will grow separately from different seeds randomly formed on the substrate 11. Therefore, seeds that are close to each other may fuse during the growth process, thereby forming a polycrystalline two-dimensional material, the lattice of which is disordered at the fusion boundary, and the electrical performance will be seriously degraded.
[0100] In the disclosed embodiments, since polycrystalline and single crystal two-dimensional thin layers cannot be identified by conventional bright field microscopes, and identification methods such as Raman and scanning electron microscopes are difficult to embed in situ into the synthesis and processing environment of two-dimensional crystals (the electron beam of the scanning electron microscope may also damage the lattice), dark field microscope imaging to identify the boundaries of single crystals is of great value. For example, dark field microscope observation photos can not only identify the boundaries of the coverage area of the two-dimensional material thin layer and the cracks of the two-dimensional crystal, but also identify the boundaries formed by the fusion of single crystal thin layers grown from different crystal seeds.
[0101] In some embodiments, please refer to Figure 8(a), the lattice disorder caused by the fusion boundary will cause the thickness of the two-dimensional thin layer to change at the atomic scale (taking single-layer MoS2 as an example, an increase or decrease of one sulfur atom or molybdenum atom diameter), which will appear as continuous bright spots with a light intensity lower than the single crystal boundary in the optical photograph of the dark field microscope.
[0102] For example, Figure 8(a) is an optical photograph of a single-layer MoS2 two-dimensional material synthesized by a CVD process under a dark field microscope (the light source is white light, and the scale is 100 μm). Further, as shown in Figure 8(b), when observing the fusion of different MoS2 single crystals, two crystal seeds that are close to each other grow separately, and the boundary formed by the fusion produces lattice disorder, which is manifested as a local thickness different from that inside the single crystal, and thus appears as a continuous bright spot with a light intensity lower than that of the single crystal boundary in the optical photograph of the dark field microscope. Among them, Figure 8(b) is an enlarged view of the single crystal fusion area in 8(a).
[0103] Further, for example, FIG8(c) and FIG8(b) are the same area, and FIG8(c) is an optical photograph of a single-layer MoS2 two-dimensional material synthesized by a CVD process under a bright field microscope (the light source is white light, and the scale is 100 μm). In the optical photograph under a bright field microscope, the fusion boundary of the single crystal cannot be observed. In this way, polycrystalline and single crystal two-dimensional thin layers cannot be identified by conventional bright field microscopes.
[0104] Some embodiments of the present disclosure provide an electronic device, including: a memory, a processor, and a display. The memory is used to store a computer program. The processor is used to run the computer program to implement the method for observing the boundaries and defects of a two-dimensional material single crystal as described in the above embodiments. The display is used to output the processing results of the processor.
[0105] In the embodiments of the present disclosure, the technical effects that can be achieved by the electronic device are the same as the technical effects that can be achieved by the method for observing the boundaries and defects of single crystals of two-dimensional materials in the aforementioned embodiments, and will not be described in detail here.
[0106] Some embodiments of the present disclosure provide a storage medium storing program instructions, which, when executed, implement the method for observing boundaries and defects of a two-dimensional material single crystal as described in the above embodiments.
[0107] In the embodiments of the present disclosure, the technical effects that can be achieved by the storage medium are the same as the technical effects that can be achieved by the method for observing the boundaries and defects of two-dimensional material single crystals in the aforementioned embodiments, and will not be described in detail here.
[0108] Some embodiments of the present disclosure provide a system for observing defects in single crystals of two-dimensional materials, including: a graphics algorithm module, an integrated circuit layout design module, and a dark field microscope. The graphics algorithm module is configured to: analyze and process optical photos of the dark field microscope, and screen out defect-free single crystal areas; the integrated circuit layout design module is configured to: design two-dimensional devices and integrated circuits based on defect-free single crystal areas.
[0109] In the disclosed embodiment, the artificially synthesized two-dimensional material sample can be based on the optical photograph obtained by the dark field microscope, and the graphic algorithm module can be used to instantly generate the boundary of the two-dimensional material thin layer and screen out the single crystal area that can be used to process the two-dimensional device with consistent performance. The above image can be further programmed to instantly generate a format suitable for the integrated circuit layout design module (such as a *.dxf format layout file), and design two-dimensional devices and integrated circuits based on the screened available area.
[0110] In some examples, see Figure 9(a), the MoS2 field effect transistors processed in batches based on the identified single crystal region (i.e., the single crystal region that has been observed under a dark field microscope to exclude cracks and the influence of the single crystal fusion boundary) show extremely high consistency of performance (transfer characteristic curve). See Figure 9(b), the field effect transistors with the same structure that are directly processed without the identified single crystal region have large performance differences (the field effect transistor channel crosses the fusion boundary).
[0111] Some embodiments of the present disclosure provide a system for observing defects in single crystals of two-dimensional materials, including: a two-dimensional material preparation device and a dark field microscope embedded in the two-dimensional material preparation device.
[0112] In the disclosed embodiments, a dark field microscope is embedded in a two-dimensional material preparation device (e.g., a CVD synthesis tube furnace) to dynamically observe the processes of two-dimensional crystal nucleation, growth, and fusion in real time. This can provide direct experimental data and theoretical analysis basis for the boundary between crystal growth and single crystal fusion formation for basic research in two-dimensional crystallography. In this way, the experimental data can further guide the controllable growth and synthesis of high-quality, large-area, single-crystalline two-dimensional materials.
[0113] In some examples, please refer to Figure 10(a), a dark field microscope optical photograph of two MoS2 single crystals fused (light source is red light, scale bar is 100μm). Among them, Figure 10(b) is an enlarged view of the single crystal fusion area in Figure 10(a). In this way, please refer to Figure 10(c), it can be inferred that the process of the growth and fusion of two MoS2 single crystals can be continuously monitored by dark field microscopy during the growth process of the sample, and it is expected to dynamically depict the entire process of the formation of the fusion boundary.
[0114] In the above-mentioned system for observing single crystal defects of two-dimensional materials, dark-field microscope imaging equipment can be easily embedded in integrated circuit layout modules, lithography machines, CVD growth tube furnaces and other environments. Through image processing algorithms and programs, efficient two-dimensional devices and two-dimensional integrated circuit EDA design can be achieved, as well as in-situ dynamic monitoring and basic research on the growth process of two-dimensional crystal materials.
[0115] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0116] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. 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 application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.
Claims
1. A method for observing the boundaries and defects of single crystals of two-dimensional materials, It is characterized in that include: Providing a sample, the sample comprising a substrate and a two-dimensional material layer located on the substrate; Observing the sample using a dark field microscope to obtain an optical image of the sample; Screening a closed area surrounded by continuous bright spots in the optical image, and extracting an area in the closed area that meets a preset area threshold as a single crystal area; If there are continuous bright spots in the single crystal region, then there are defects in the single crystal region in the two-dimensional material layer.
2. The method for observing the boundaries and defects of a two-dimensional material single crystal according to claim 1, It is characterized in that If there are continuous bright spots in the single crystal region whose light intensity is less than that at the boundary of the single crystal region, then there are a plurality of single crystal regions whose boundaries are fused in the two-dimensional material layer.
3. The method for observing the boundaries and defects of a two-dimensional material single crystal according to claim 1, It is characterized in that The step of observing the sample using a dark field microscope to obtain an optical image of the sample comprises: The light source provides visible light as incident light; The incident light is incident on the sample at an oblique angle from outside the objective lens in the dark field microscope, and the incident light irradiated on the sample is Rayleigh scattered; The scattered light is collected by an optical information receiving device in the dark field microscope, and converted into an optical photograph by an imaging device in the dark field microscope.
4. The method for observing the boundaries and defects of a two-dimensional material single crystal according to claim 3, It is characterized in that The light source also provides red light as incident light.
5. The method for observing the boundaries and defects of a two-dimensional material single crystal according to claim 1, It is characterized in that The shape of the closed area is a regular pattern.
6. The method for observing the boundaries and defects of a two-dimensional material single crystal according to claim 1, It is characterized in that The substrate comprises a flat substrate; and the dark field microscope comprises an epi-illumination dark field microscope.
7. An electronic device, It is characterized in that include: Memory for storing computer programs; A processor, configured to run the computer program to implement the method for observing boundaries and defects of a two-dimensional material single crystal according to any one of claims 1 to 6; A display is used to output the processing result of the processor.
8. A storage medium storing program instructions, It is characterized in that When the program instructions are executed, the method for observing boundaries and defects of single crystals of two-dimensional materials as described in any one of claims 1 to 6 is implemented.
9. A system for observing the boundaries and defects of single crystals of two-dimensional materials. It is characterized in that include: A graphics algorithm module, an integrated circuit layout design module and a dark field microscope; wherein the graphics algorithm module is configured to: analyze and process the optical photographs of the dark field microscope, and screen out defect-free single crystal areas; the integrated circuit layout design module is configured to: design two-dimensional devices and integrated circuits based on the defect-free single crystal areas.
10. A system for observing the boundaries and defects of single crystals of two-dimensional materials. It is characterized in that include: A two-dimensional material preparation device and a dark field microscope embedded in the two-dimensional material preparation device.