Method and system for identifying two-dimensional material pseudo single crystal, electronic equipment and storage medium

Abstract

The invention relates to a method and system for identifying a two-dimensional material pseudo single crystal, electronic equipment and a storage medium. The method for identifying the two-dimensional material pseudo single crystal comprises the following steps: providing a sample which comprises a flat substrate and a two-dimensional material layer positioned on the flat substrate; observing the two-dimensional material layer by using a dark field microscope, and obtaining an optical image of the two-dimensional material layer; taking a closed area enclosed by the bright boundary line in the optical image as a target area; in response to the same brightness in the target area, determining that the target area is a true single crystal; and in response to different brightness presented in the target area, determining that the target area is the pseudo single crystal. According to the invention, the pseudo single crystal in the two-dimensional material can be quickly identified at low cost without damage, and the performance of the device is improved by using the reliable true single crystal.

Description

Technical Field

[0001] This disclosure relates to the field of two-dimensional material characterization technology, and in particular to a method and system for identifying pseudo single crystals of two-dimensional materials, electronic devices, and storage media. Background Technology

[0002] Two-dimensional materials are of great value for the research of novel electronic devices and integrated circuits. Among them, molybdenum disulfide (MoD) is one of the more extensively studied materials, and monolayer MoD is considered an ideal alternative to silicon. Currently, the fabrication of devices requires the use of single-crystal regions of MoD; therefore, selecting high-quality single-crystal MoD regions is crucial.

[0003] However, single-crystal regions of two-dimensional materials identified by ordinary bright-field microscopy may contain core-shell structures with different electrical properties, which can lead to unpredictable performance of fabricated devices. Although such core-shell structures can be identified by instruments such as Raman spectrometers, scanning electron microscopes, photoluminescence spectrometers, and atomic force microscopes, these instruments are complex and slow to image, and some may cause radiation damage or mechanical contact damage to the sample, thus preventing their application in existing integrated circuit processes.

[0004] Therefore, how to quickly, cost-effectively, and non-destructively identify pseudo single crystals in two-dimensional materials, and then use reliable true single crystals to improve device performance, is an urgent problem to be solved. Summary of the Invention

[0005] Based on this, the present disclosure provides a method and system, electronic device, and storage medium for identifying pseudo single crystals in two-dimensional materials, which can quickly, cost-effectively, and non-destructively identify pseudo single crystals in two-dimensional materials, thereby improving device performance using reliable true single crystals.

[0006] To achieve the above objectives, in a first aspect, some embodiments of this disclosure provide a method for identifying pseudo-single crystals of two-dimensional materials, comprising the following steps:

[0007] Provide a sample, which includes a flat substrate and a two-dimensional material layer on the flat substrate;

[0008] Two-dimensional material layers were observed using dark-field microscopy, and optical images of the two-dimensional material layers were obtained;

[0009] The closed region in the optical image enclosed by a bright boundary line is taken as the target region;

[0010] If the target region exhibits the same brightness, it is determined to be a true single crystal; if the target region exhibits different brightness, it is determined to be a pseudo single crystal.

[0011] In some embodiments of this disclosure, the pseudo-single crystal has a core-shell structure. The core-shell structure includes a core region and a shell region that surrounds the core region. The brightness of the core region is greater than that of the shell region. The core region and the shell region have different electrical properties.

[0012] In some embodiments of this disclosure, the method for identifying pseudo single crystals of two-dimensional materials further includes the following steps:

[0013] Convert optical images to grayscale;

[0014] Calculate the average gray value of the core region and the shell region.

[0015] In some embodiments of this disclosure, the average gray value of the core region is greater than the average gray value of the shell region. The scattering intensity of the core region is greater than the scattering intensity of the shell region.

[0016] In some embodiments of this disclosure, the thickness of the pseudo-single crystal located in the core region is the same as the thickness of the pseudo-single crystal located in the shell region.

[0017] In some embodiments of this disclosure, observing a two-dimensional material layer using a dark-field microscope and acquiring optical images of the two-dimensional material layer includes:

[0018] The light source provides visible light as the incident light;

[0019] The incident light rays enter the sample at an oblique angle from outside the objective lens in the dark field microscope, and the incident light rays illuminating the sample are scattered.

[0020] Scattered light is collected using the optical information receiving device in a dark-field microscope, and converted into an optical image using the imaging device in a dark-field microscope.

[0021] In some embodiments of this disclosure, the light source also provides white light, monochromatic light, yellow light, and red light as incident light.

[0022] Secondly, embodiments of this disclosure also 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 identifying pseudo-single crystals of two-dimensional materials as described in the foregoing embodiments. The display is used to output the processing results of the processor.

[0023] Thirdly, this disclosure also provides a storage medium storing program instructions, which, when executed, implement the method for identifying pseudo-single crystals of two-dimensional materials as described in the foregoing embodiments.

[0024] Fourthly, embodiments of this disclosure also provide a system for identifying pseudo-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 images from the dark-field microscope and screen out true single crystals. The integrated circuit layout design module is configured to design two-dimensional devices and integrated circuits based on true single crystals.

[0025] The embodiments disclosed herein may have, or at least have, the following advantages:

[0026] In this embodiment, a dark-field microscope is used to observe a two-dimensional material layer located on a flat substrate. The substrate is imaged against a black background, and areas on the two-dimensional material layer with significant height variations are imaged in bright colors. Thus, using optical images, the closed region enclosed by bright boundary lines is first identified as the target region (including true single crystals and pseudo-single crystals). Then, it is observed whether the target region exhibits the same brightness. In this way, by observing whether the target region exhibits the same brightness, pseudo-single crystals exhibiting different brightness can be quickly identified. Pseudo-single crystals include core regions with poor electrical properties. Therefore, this disclosure, by using a dark-field microscope to observe a two-dimensional material layer located on a flat substrate, can efficiently, accurately, and quickly locate core regions with poor electrical properties.

[0027] In addition, compared with existing Raman spectrometers, scanning electron microscopes, atomic force microscopes, and photoluminescence spectrometers, visible light dark-field microscopes have advantages such as better signal quality, easier practical application, lower equipment cost, and no electronic damage to samples.

[0028] Furthermore, the light source disclosed herein provides visible light as the incident light, which can also be replaced with white light, monochromatic light, yellow light, and red light, thereby ensuring that the photoresist is not damaged. This facilitates its embedding into semiconductor integrated circuit processing technology and is of great value for promoting the development of two-dimensional semiconductor devices and integrated circuits, including molybdenum disulfide. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating a method for identifying pseudo single crystals in two-dimensional materials, provided in some embodiments.

[0030] Figure 2 This is a flowchart illustrating step S200 in a method for identifying pseudo single crystals of two-dimensional materials provided in some embodiments;

[0031] Figure 3 This is a flowchart illustrating another method for identifying pseudo single crystals of two-dimensional materials provided in some embodiments;

[0032] Figure 4This is a schematic diagram of the structure obtained after step S100 in a method for identifying pseudo single crystals of two-dimensional materials provided in some embodiments;

[0033] Figure 5 Schematic diagram of dark-field microscopy scattering imaging principle;

[0034] Figure 6a An optical image of a bright-field microscope under one type of light, provided in some embodiments of a method for identifying pseudo single crystals of two-dimensional materials; Figure 6b An optical image of a bright-field microscope under another light source in one of the methods for identifying pseudo single crystals of two-dimensional materials provided in some embodiments; Figure 6c An optical image of a bright-field microscope under another light source in one of the methods for identifying pseudo single crystals of two-dimensional materials provided in some embodiments; Figure 6d An optical image from a dark-field microscope provided in some embodiments of a method for identifying pseudo single crystals of two-dimensional materials;

[0035] Figure 7a A grayscale image of a dark-field microscope provided in some embodiments for a method of identifying pseudo single crystals of two-dimensional materials; Figure 7b Large-area local atomic force microscopy images of the core-shell structure (long cross-sectional height from wafer to shell to core: macroscopic long straight line 512 points; short step height from wafer to shell: detail short straight line 512 points). Figure 7c The height curve of the short-distance step from wafer to shell (corresponding to) Figure 7b (5 short straight lines and 512-point curves with 100nm detail in the middle). Figure 7d The curve represents the long-distance cross-sectional height of the wafer → shell → core (corresponding to the macroscopic long straight line at point 512 in Figure b). Figure 7e The right image shows three locations each for the wafer, shell region, and core region (corresponding to...). Figure 7b Atomic force microscopy images of individual points in the image (128 nm × 128 nm square region, 512 × 512 resolution, lateral stepping at the single-atom scale). Figure 7e The left figure in the image is the Gaussian distribution plot fitted using the statistical standard deviation;

[0036] Figure 8 In one embodiment of a method for identifying pseudo single crystals of two-dimensional materials, the brightness of the wafer, shell region, and core region is proportional to the fourth power of its roughness.

[0037] Figure 9a A schematic diagram of the tip passivation effect of an atomic force microscope probe on a single-atom-scale rough surface. Figure 9b correspond Figure 7b Five 2μm detail short straight lines with 512 points (fitted to an error function) are compared with the short step curve of the ideal wafer → shell region. Figure 9c To address the tip passivation effect in atomic force microscopy imaging, and by analogy with the convolution effect of a Gaussian convolution kernel, the two-dimensional spatial Gaussian function (convolution kernel) at the tip of the atomic force microscopy probe is calculated.

[0038] Figure 10a Dark-field microscopy image of a monolayer of molybdenum disulfide grown under sulfur-deficient conditions; Figure 10b The 30 field-effect transistors fabricated for a perfect single-crystal region exhibit highly consistent transfer characteristics; Figure 10c The five field-effect transistors fabricated in the pseudo-single-crystal shell region exhibit transfer characteristics consistent with those of a perfect single-crystal field-effect transistor, while the five field-effect transistors fabricated in the core region show degraded and inconsistent electrical performance.

[0039] Explanation of reference numerals in the attached figures:

[0040] 1-Sample; 11-Wafer; 12-Two-dimensional material layer; 2-Incident ray; 3-Objective lens; 4-Scattered ray; 5-Optical image; 51-Target area; 51'-Target area in bright-field microscope optical image; 511-Core region; 512-Shell region; 6-Mirror. Detailed Implementation

[0041] To facilitate understanding of this disclosure, a more complete description will now be given with reference to the accompanying drawings, in which preferred embodiments of the present disclosure are shown. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough and complete understanding of the disclosure will be achieved.

[0042] Unless otherwise defined, all technical and scientific terms used in this disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used in this disclosure includes any and all combinations of one or more of the associated listed items.

[0043] When using the terms “comprising,” “having,” and “including” as described in this disclosure, another component may be added unless explicitly qualifying terms such as “only,” “consisting of,” etc. are used. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0044] In the description of this disclosure, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0045] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0046] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0047] In this disclosure, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0048] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intermediate element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element present. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this disclosure are for illustrative purposes only and do not represent the only possible implementation.

[0049] Embodiments of the invention are described herein with reference to schematic diagrams that serve as preferred embodiments (and intermediate structures) of this disclosure, thus allowing for the anticipation of variations in the illustrated shape due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of this disclosure should not be limited to the specific shape of the area shown herein, but rather include shape deviations due to, for example, manufacturing techniques.

[0050] Two-dimensional semiconductors, with their natural nanosheet shape, are of great value for the research of novel electronic devices, such as gate-all-around (GAA) transistors and integrated circuits. Molybdenum disulfide (MoD) is one of the more extensively studied types, with monolayer MoD considered an ideal alternative to silicon. Currently, MoD used for integrated circuit fabrication primarily relies on chemical vapor deposition (CVD) growth. However, MoD's mobility is not particularly high, and its two-dimensional morphology means that even minor defects, doping, and wrinkles can cause significant damage. Therefore, when fabricating devices using CVD-grown MoD, the preferred method is typically a single-layer region, marked by a triangle, considered a single crystal, rather than a large-area polycrystalline monolayer film formed by fusing numerous single crystals, as seen in CVD graphene (which tolerates mobilities decreasing from hundreds of thousands to thousands but remains uniform). Thus, selecting high-quality single-crystal MoD regions is crucial.

[0051] Current research generally suggests that single-crystal monolayer CVD molybdenum disulfide (MoD) single crystals can be easily identified using ordinary optical microscopes. However, experimental studies show that the quality consistency of MoD devices fabricated in this way is not high, generally failing to meet integration requirements. Even now, different studies report inconsistent carrier mobilities for MoD, indicating that current microscopic selection techniques for single-crystal MoD are not entirely reliable. A "core-shell" pseudo-single crystal growth mechanism exists in monolayer MoD; that is, a seemingly perfect monolayer MoD triangle actually contains core-shell regions with different electrical properties, leading to unpredictable device performance. Although theoretically the reactant concentration in a small system is isotropic, "core-shell" pseudo-single crystals still have a small probability of appearing, making accurate identification and exclusion techniques necessary. While this core-shell structure can be identified using Raman spectroscopy, scanning electron microscopy, and photoluminescence spectroscopy, these devices are complex and slow to image, and some can even cause electronic damage to the sample, thus preventing their integration into existing integrated circuit processes.

[0052] Based on this, the present disclosure provides a method and system for identifying pseudo single crystals in two-dimensional materials, an electronic device, and a storage medium, which can quickly, cost-effectively, and non-destructively identify pseudo single crystals in two-dimensional materials, thereby using reliable true single crystals to improve device performance.

[0053] Please see Figure 1 This disclosure provides a method for identifying pseudo single crystals in two-dimensional materials, including steps S100 to S400.

[0054] S100 provides a sample, which includes a flat substrate and a two-dimensional material layer on the flat substrate.

[0055] The S200 uses a dark-field microscope to observe two-dimensional material layers and acquire optical images of the two-dimensional material layers.

[0056] S300 uses the closed region in the optical image enclosed by a bright boundary line as the target region.

[0057] S400 determines that the target region is a true single crystal if it exhibits the same brightness within the target region, and determines that the target region is a pseudo single crystal if it exhibits different brightness within the target region.

[0058] In this embodiment, a dark-field microscope is used to observe a two-dimensional material layer located on a flat substrate. The wafer is imaged against a black background, and areas on the two-dimensional material layer with significant height variations are imaged in bright colors. Thus, through optical imaging, the closed region enclosed by the bright boundary line is first identified as the target region (including true single crystals and pseudo single crystals). Then, it is observed whether the target region exhibits the same brightness. In this way, by observing whether the target region exhibits the same brightness, pseudo single crystals exhibiting different brightness can be quickly identified. Pseudo single crystals include core regions with poor electrical properties. Therefore, this disclosure, by using a dark-field microscope to observe a two-dimensional material layer located on a flat substrate, can efficiently, accurately, and quickly locate core regions with poor electrical properties.

[0059] In addition, compared with existing Raman spectrometers, scanning electron microscopes, atomic force microscopes, and photoluminescence spectrometers, dark-field microscopy has advantages such as better signal quality, easier practical application, lower equipment cost, and no electronic damage to samples.

[0060] In some embodiments, the pseudo-single crystal has a core-shell structure. The core-shell structure includes a core region and a shell region that surrounds the core region. The brightness of the core region is greater than that of the shell region. The core region and the shell region have different electrical properties.

[0061] In some embodiments, please refer to Figure 2 Step S200 involves observing the two-dimensional material layer using a dark-field microscope and acquiring an optical image of the two-dimensional material layer, including steps S210 to S230.

[0062] S210, the light source provides visible light as the incident light.

[0063] S220: The incident light rays enter the sample at an oblique angle from outside the objective lens of the dark field microscope, and the incident light rays illuminating the sample are scattered.

[0064] S230 uses an optical information receiving device in a dark-field microscope to collect scattered light and uses an imaging device in a dark-field microscope to convert it into an optical image.

[0065] It is important to note here that visible light includes rays in the vicinity of the visible light band (wavelengths of approximately several hundred nanometers).

[0066] In some embodiments, the light source also provides white light, monochromatic light, yellow light, and red light as incident light.

[0067] In some embodiments, please refer to Figure 3 The method for identifying pseudo single crystals of two-dimensional materials also includes steps S510~S520.

[0068] S510 converts optical images to grayscale.

[0069] S520 calculates the average gray value of the core and shell regions.

[0070] In some embodiments, the average gray value of the core region is greater than the average gray value of the shell region. The scattering intensity of the core region is greater than the scattering intensity of the shell region.

[0071] In some embodiments of this disclosure, the thickness of the pseudo-single crystal located in the core region is the same as the thickness of the pseudo-single crystal located in the shell region.

[0072] It should be noted that, in the above embodiments, the execution order of each step in the method is not strictly limited. These steps may not necessarily be executed in the described order, but may be executed in other ways. Moreover, at least a portion of any step may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but may be executed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0073] To more clearly illustrate the method for observing the boundaries and defects of single crystals in two-dimensional materials provided in the above embodiments, the following is combined with... Figures 4-10c The method is described in detail.

[0074] In step S100, please refer to Figure 4 Sample 1 is provided, which includes a flat substrate and a two-dimensional material layer 12 located on the flat substrate.

[0075] In some embodiments, the flat substrate includes wafer 11.

[0076] In some embodiments, wafer 11 comprises silicon dioxide (SiO2) and / or silicon (Si). The two-dimensional material layer comprises a monolayer of molybdenum disulfide.

[0077] In some examples, the thickness of wafer 11 ranges from 200nm to 400nm. For example, the thickness of wafer 11 can be 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, 320nm, 340nm, 360nm, 380nm, or 400nm, etc.

[0078] For example, Sample 1 includes a monolayer of molybdenum disulfide grown on a 300 nm SiO2 / Si wafer. The synthesis conditions for the monolayer molybdenum disulfide can be referenced from existing processes and will not be detailed here.

[0079] In step S210, please refer to Figure 5 The light source provides visible light as the incident ray.

[0080] In some embodiments, the light source also provides white light, monochromatic light, yellow light, and red light as incident light.

[0081] The light source disclosed herein provides visible light as the incident light, which can also be replaced with white light, monochromatic light, yellow light, and red light, thereby ensuring that the photoresist is not damaged. This facilitates its embedding into semiconductor integrated circuit processing technology and is of great value for promoting the development of two-dimensional semiconductor devices and integrated circuits, including molybdenum disulfide.

[0082] In step S220, please refer to... Figure 5 The incident light 2 enters the sample 1 at an inclined angle from outside the objective lens 3 in the dark field microscope, and the incident light 2 illuminating the sample 1 is scattered.

[0083] Here, the imaging principle is based on the Reighley-Rice scattering theory.

[0084] In some examples, please refer to [link / reference]. Figure 5 The dark-field microscope also includes a reflecting mirror 6. The reflecting mirror 6 is used to change the direction of several parallel beams.

[0085] In addition, the light source shines at an angle from outside the objective lens 31 onto the sample 1, and the reflected light will not enter the objective lens 3 / camera.

[0086] In step S230, please continue reading. Figure 5 Scattered light 4 is collected using an optical information receiving device in a dark-field microscope, and converted into an optical image 5 using an imaging device in a dark-field microscope.

[0087] In step S300, please refer to Figures 6a-6d The closed region enclosed by the bright boundary line in the optical image 5 is taken as the target region 51.

[0088] It is important to note that, in order to ensure that the pixel values ​​of the photos accurately reflect the true brightness information, all beauty functions have been turned off, and the light intensity and integration time are set to prevent brightness saturation (>255).

[0089] In some embodiments, when using CVD-grown molybdenum disulfide fabrication devices, triangular single-crystal regions are used.

[0090] Accordingly, in some embodiments, the shape of the enclosed region includes a triangle.

[0091] In step S400, please continue reading. Figures 6a-6d If the target region 51 exhibits the same brightness, the target region 51 is determined to be a true single crystal; if the target region 51 exhibits different brightness, the target region is determined to be a pseudo single crystal.

[0092] In some embodiments, such as Figure 6a , Figure 6b , Figure 6c As shown, when observed with a bright-field microscope, molybdenum disulfide in the target region 51' appears to be a perfect single-layer single crystal (true single crystal) regardless of how the light intensity is adjusted.

[0093] In some embodiments, please refer to Figure 6d When observed using a dark-field microscope, the molybdenum disulfide in target region 51 can be identified as a pseudo-single crystal. The pseudo-single crystal has a core-shell structure. This structure includes a core region 511 and a shell region 512 that surrounds the core region. The brightness of the core region 511 is greater than that of the shell region 512. The core region 511 and the shell region 512 have different electrical properties.

[0094] In some embodiments, such as Figure 6d As shown, a triangular target region 51 exhibits different brightness levels, confirming that target region 51 is a pseudo-single crystal with a core-shell structure. From an optical perspective, the core region 511 and the shell region 512 should both be monolayer films composed of molybdenum disulfide molecules, resulting in essentially the same refractive index and consistent thickness. This is because, according to Fresnel's Law for observing two-dimensional materials using bright-field microscopy, regardless of differences in refractive index or thickness between the core region 511 and the shell region 512, they can always be distinguished under a bright-field microscope. However, based on... Figure 6d The identifiable facts and the principle of dark-field microscopy imaging show that the difference in morphology between the molybdenum disulfide core region 511 and the shell region 512 is due to differences in roughness.

[0095] In some embodiments, the thickness of the pseudo-single crystal located in the core region 511 is the same as the thickness of the pseudo-single crystal located in the shell region 512. Thus, the core region 511 and the shell region 512 are difficult to distinguish under a bright-field microscope.

[0096] In step S510, please refer to Figure 7a The optical image is converted to grayscale.

[0097] In some examples, in order to quantitatively analyze the dark-field microscopy imaging principle of core-shell structures, the optical images of the dark-field microscope were grayscaled (RGB average grayscale).

[0098] In step S520, please continue reading. Figure 7a Calculate the average gray value of the core region 511 and the shell region 512.

[0099] In some examples, such as Figure 7aAs shown, the average grayscale values ​​of wafer 11, core region 511, and shell region 512 were calculated. The average grayscale value of wafer 11 was 44.83; the average grayscale value of core region 511 was 145.17; and the average grayscale value of shell region 512 was 39.26. This result indicates that the scattering intensity of core region 511 is significantly greater than that of shell region 512 and wafer 11, therefore it should have a larger roughness. Therefore, the core-shell structure was imaged using an atomic force microscope (AC160TS probe, non-contact mode). Figure 7b As shown, the molybdenum disulfide region is clear, but the distinction between areas where a core-shell structure should exist is not easily discernible. Based on this image, a series of short, easily leveled, straight lines were selected along the edge from wafer 11 to the molybdenum disulfide shell region 512 for measurement. Figure 7c As shown, the average height near the edge of molybdenum disulfide is about 0.682 nm higher than that of wafer 11, confirming the morphology of monolayer molybdenum disulfide. Simultaneously, extraction... Figure 7b The linear measurement data spanning wafer 11, shell region 512, and core region 511 are as follows: Figure 7d As shown. The core-shell region 512 above molybdenum disulfide can be fitted with a straight line, and its consistent height is consistent with the core-shell thickness indicated by the bright-field micrograph, thus confirming the conclusion that it is not visible in the bright field.

[0100] In some embodiments, the average gray value of the core region 511 is greater than the average gray value of the shell region 512. The scattering intensity of the core region 511 is greater than the scattering intensity of the shell region 512.

[0101] It is important to note here that the scattering intensity is affected by the surface roughness of the region, but is independent of the chemical composition of the two-dimensional material.

[0102] Furthermore, in some embodiments, to accurately verify whether there is a significant difference in roughness between the core region 511 and the shell region 512, three 128nm × 128nm square regions (corresponding to) were selected in the wafer 11, the core region 511, and the shell region 512, respectively. Figure 7a In the middle position), a 512×512 resolution height image was performed, and leveling calibration was uniformly performed using the average height values ​​of all pixels in each sub-image. Figure 7eAs shown. The standard deviations of the heights of wafer 11, core region 511, and shell region 512 were calculated and used as their surface roughness indices: 0.132 nm, 0.121 nm, and 0.172 nm, respectively. This result shows that the roughness of the molybdenum disulfide shell region 512 is almost equal to that of wafer 11, which can be understood as an ideal single crystal covering the surface of wafer 11. The core region 512 has a greater roughness, indicating a crystal structure. Furthermore, considering that dark-field microscopy relies on scattered light rather than reflected light for imaging, the varying roughness of the horizontal sample surface, leading to different scattered light intensities, should be the reason for identifying the core-shell structure in dark-field microscopy. Based on this, it is speculated that the Reighley-Rice scattering theory, applicable to dark-field observation of flat samples, may be used to explain the experimental phenomena.

[0103] Furthermore, in some embodiments, a visible light beam (380nm-750nm) with a wavelength of 13.8° is incident around the object at a constant incident angle of 13.8°. After being scattered by a region on the surface of the molybdenum disulfide sample, it enters the objective lens at a scattering angle (0°–7.5°), forming a dark-field image. First, assuming the input light is of a single wavelength, the grayscale value of the dark-field image formed by the observation area at a single scattering angle can be expressed according to the Rayleigh-Rice vector perturbation surface scattering model as follows:

[0104]

[0105] Where, Wafer 11, shell region 512, core region 511, The effective incident light intensity depends on the quantum efficiency of the camera and objective lens in responding to light of different wavelengths; This indicates the incident angle corresponding to the sample surface. and scattering angle The geometric mean of the specular reflection coefficient is approximately constant for wafer samples; Topography of the scattering region of the sample The two-dimensional spatial power spectral density corresponds to the effective wavelength of the incident light. Since the incident light is incident in a 360° circumferential pattern, the independent variable in the equation... The effective frequency of spatial sampling is determined by the incident light wavelength and the microscope.

[0106] For the two-dimensional spatial power spectral density of the sample surface morphology in formula (1) Considering that sample wafer 11 is a flat amorphous layer composed of silicon dioxide (SiO2), the isotropic random distribution of surface atoms determines its morphology. The statistical characteristics of the elevation morphology of each region are then expressed using a Gaussian autocorrelation function:

[0107]

[0108] In formula (2), The roughness (height standard deviation) of wafer 11, shell region 512, and core region 511 respectively; Let x and y be the respective distances in the xOy plane, representing the texture scale. For samples whose surface morphology is determined by the amorphous SiO2 layer and lacks artificial periodic texture, it can be considered that... is with A considerable length in the angstrom class (ie, Therefore, the two-dimensional spatial power spectral density function of each region can be derived from... bilateral Fourier transform Find:

[0109]

[0110]

[0111] Then, the two-dimensional spatial frequency of the scattering imaging Substituting into formula (3), the spatial power spectral density values ​​for each observation area can be obtained:

[0112]

[0113] It is particularly noteworthy that when the prerequisites required by the Reighley-Rice scattering model are met, i.e., the roughness of the scattering region is much smaller than the wavelength of the incident light ( If the exponent term in formula (4) approaches 1, then the power spectral density can be approximated with a very high accuracy:

[0114]

[0115] Therefore, substituting formula (5) into formula (1), we can see that the light intensity of a single wavelength at a fixed scattering angle is related to the sample roughness by the fourth power:

[0116]

[0117]

[0118] Furthermore, if the incident light used in the experimental observation is polychromatic visible light... λ∈[ λ min , λ max ] (e.g., the incident light spectrum used in this disclosure is 380nm–750nm), and the angle at which the objective lens receives scattered light is within a certain range. θ s ∈[0°, θ s_max ] (e.g., as in this disclosure) 7.5°), if the image has no exposure saturation ( 255), then from formula (6), it can be deduced that the gray value of each region in the actual dark field photomicrograph should still be proportional to the fourth power of the corresponding roughness:

[0119]

[0120]

[0121]

[0122] Based on the above analysis, it is believed that the Reighley-Rice scattering model can perfectly explain the experimental phenomenon of identifying core-shell structures using dark-field microscopy. Slight surface roughness variations in the molybdenum disulfide sample, amplified to the fourth power, result in significant contrast in the dark-field photographs. Extraction... Figure 7e various regions in China Experimental roughness measurement of wafer 11, shell region 512, and core region 511. And according to formula (7), the gray values ​​of each region in the dark field photomicrograph are compared. Fitting was performed as follows Figure 8 As shown. The results show that when When, the relationship to the fourth power The high goodness of fit indicates that dark-field microscopy is well suited for characterizing two-dimensional materials with angstrom-level roughness without artificial textures. It also suggests that using longer wavelength visible light is more conducive to satisfying the approximation conditions of Equation (5) and is more beneficial to improving the accuracy of Equation (7).

[0123] but Figure 7d The step curve shown, from wafer 11 to molybdenum disulfide (shell region 512), exhibits a gentle upward trend, which does not conform to the known sharp step change curve. This affects the accuracy of the measurement results for the surface roughness of molybdenum disulfide. Figure 7e Some doubt arose, although the height variation was consistent with the thickness of the monolayer molybdenum disulfide. It was believed that such measurement results stemmed from the AFM probe's insufficient sharpness; its nanometer-scale tip radius of curvature was larger than the atomic-scale morphology of the molybdenum disulfide sample surface, resulting in a tip passivation effect that gave the observation results a "smooth" appearance. Figure 9a ). That is, Figure 7e AFM measurement of roughness value It may be less than its corresponding truth value. This makes the validity of formula (7) questionable. Therefore, an attempt is made to recover the true roughness value through deconvolution. And confirm the prerequisite for the Reighley-Rice scattering model to hold in formula (7). It is still satisfied.

[0124] First, the parameters of the AFM probe tip passivation effect are quantitatively estimated. Considering AFM imaging ( Figure 9a This depends on the weighted sum of van der Waals short-range forces between the silicon atom at the tip and the sample alignment point. The tip radius of curvature (~7 nm) means that the observation of a single atom is subject to the combined effects of a vast number of atoms. Therefore, according to the central limit theorem, the observation of the positional morphology of a single atom on the sample surface by the tip, including passivation effects, can be represented as a convolution with a two-dimensional Gaussian clock pulse function.

[0125]

[0126] The normalized two-dimensional Gaussian function in formula (8) is expressed as:

[0127]

[0128] Formula (9) contains only one unknown parameter—the needle tip passivation effect parameter. (The lateral resolution parameter) needs to be quantitatively estimated. It can be estimated by the specific known step morphology formed from the edge of the monolayer molybdenum disulfide (shell region 512) to the wafer, and its consistency in the y-axis direction can be used to simplify the two-dimensional plane problem of convolution of Equations (8) and (9) into one-dimensional convolution. It is known that the theoretical step morphology of molybdenum disulfide in the x-axis direction is:

[0129]

[0130] like Figure 9b As shown, Figure 7d Multiple 100nm detail curves observed in actual measurements were integrated and compared with the step function corresponding to the theoretical step morphology of a molybdenum disulfide monolayer single crystal. At this point, in the x-axis direction, the observed curves... It should be a step function. Compared to a one-dimensional Gaussian function expressed along the x-axis. Convolution:

[0131]

[0132]

[0133] because It is a step function, and the result of the above convolution is actually a step function. The original function, i.e., an error function:

[0134]

[0135]

[0136] The constants in formula (11) should be selected according to the actual situation. nm, can be used function pairs Figure 9b A global regression fitting is performed on multiple experimental observation curves. When the residuals are minimized... The only unknown parameter in the process achieves the optimal value. nm. Since the two-dimensional convolution kernel describing the AFM tip passivation effect is isotropic. nm can be directly used in equation (7) Therefore, the passivation effect of the AFM tip was quantified, which allows for further quantitative calculation of the true roughness value of the core-shell structure surface.

[0137] like Figure 9c As shown, the surface morphology of a small region in the molybdenum disulfide sample It can be viewed as a two-dimensional discrete random process on the xOy plane. If divided according to the single-atom scale... Pixels (e.g., in this disclosure, a 128nm × 128nm region is divided into 512 × 512 = 262144 pixels), according to the central limit theorem, after removing the average height, each pixel ( The height of the object should follow a one-dimensional normal distribution. In the formula, Wafer 11, shell region 512, core region 511. The actual height value of each pixel observed by AFM. It is the corresponding truth value and all surrounding pixel values The spatial low-pass filtering effect (smoothing) after convolution weighting. Based on the Nyquist sampling theorem, under the condition that the AFM probe is not "sharp" enough ( Even if the scale does not meet the requirement of non-destructive observation being less than half the pixel size, The function is known; it needs to be determined by actual measurement. Accurately restore the true morphology of the sample That's also impossible. However, regarding standard deviation... In other words, statistical parameters such as surface roughness can still be obtained through measured values. Inversely calculate the true value of roughness .

[0138] First, such as Figure 9c As shown, the AFM tip convolution function in formula (9) By pixel size (scan step distance) Discretization ), and shortened to Pixel convolution kernel, then Any pixel within the pixel observation area corresponding The convolution weighting coefficients are:

[0139]

[0140] In formula (12), the letters Considering the values ​​in the convolution kernel If it is a centrosymmetric distribution, then any pixel The observed values ​​are:

[0141]

[0142] From formula (13), it can be seen that after convolution... yes A linear combination of the values ​​of the surrounding pixels. Therefore, It also follows a one-dimensional normal distribution. , variance Should be The product of the variance and the sum of squares of all weight coefficients:

[0143]

[0144] when From the scale of a single atom, and Formula (9) is so large that it can be ignored. To formula (10) When there is a truncation error between the two, the summation in formula (14) can be used to approximate the return to the definite integral. ),Right now:

[0145]

[0146]

[0147] Therefore, it can be concluded that there is a linear relationship between the true value and the measured value of roughness:

[0148]

[0149] Known conditions 6.75nm 128 / 512 = 0.25 nm and the experimentally observed roughness values ​​of various regions on the surface of the molybdenum disulfide sample. 0.132nm 0.121nm Substituting 0.172nm into equation (9), the corresponding true roughness value is estimated to be approximately 0.724nm 0.795nm 1.023 nm is still smaller than the minimum wavelength used in visible light dark-field microscopy. 380nm is more than two orders of magnitude smaller. This confirms that the fourth power relationship described by formula (7) is correct. The Reighley-Rice scattering model still holds true and can accurately explain the experimental results of identifying core-shell structures using visible light dark-field microscopy images disclosed in this paper. Figure 6d ).

[0150] To further verify the accuracy of dark-field optical microscopy in identifying core-shell pseudo-single crystal regions and its value in improving the electrical performance consistency of mass-produced two-dimensional transistors, a monolayer molybdenum disulfide sample containing a relatively large number of core-shell pseudo-single crystals was specifically synthesized via sulfur under-suppression synthesis, such as... Figure 10a As shown, the perfect single-crystal region, shell region 512, and core region 511 of molybdenum disulfide, identified by dark-field microscopy, were used to support a field-effect transistor using the same processing technology, and its electrical characteristics were tested. Figure 10b As shown, 30 field-effect transistors fabricated from perfect single-crystal molybdenum disulfide regions exhibit highly consistent transfer characteristics, with a homogeneity level almost equivalent to that of single-crystal silicon field-effect transistors, thus theoretically allowing for further integration. Simultaneously, it was found that molybdenum disulfide field-effect transistors fabricated using shell regions with pseudo-single-crystal outer rings also possess transfer characteristics almost identical and consistent with those of perfect single-crystal field-effect transistors. Figure 10c The dark red curve of the 5th curve in the middle. In contrast, molybdenum disulfide field-effect transistors fabricated from the core region exhibit weak and inconsistent transfer characteristics ( Figure 10c (The other 5 curves of Zhongtiao). The above results show that for current CVD-synthesized two-dimensional molybdenum disulfide materials, eliminating the nucleus region in pseudo-single crystals can ensure the consistency of electrical properties and the potential for device integration. Furthermore, the visible light dark-field microscopy disclosed in this publication enables efficient and accurate selection of usable single-crystal regions, making it a semiconductor characterization tool with significant practical value.

[0151] This disclosure provides an electronic device, including a memory, a processor, and a display, among other embodiments. The memory stores a computer program. The processor runs the computer program to implement the method for identifying pseudo-single crystals of two-dimensional materials as described in the foregoing embodiments. The display outputs the processing results from the processor.

[0152] In this embodiment, the technical effects achieved by the electronic device are the same as those achieved by the method for identifying pseudo single crystals of two-dimensional materials in the foregoing embodiments, and will not be described in detail here.

[0153] This disclosure provides, in some embodiments, a storage medium storing program instructions. When executed, the program instructions implement the method for identifying pseudo-single crystals of two-dimensional materials as described in the foregoing embodiments.

[0154] In this embodiment, the technical effects achieved by the storage medium are the same as those achieved by the method for identifying pseudo single crystals of two-dimensional materials in the foregoing embodiments, and will not be described in detail here.

[0155] This disclosure provides a system for observing single-crystal defects in 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 images from 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 the defect-free single-crystal regions.

[0156] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0157] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for identifying pseudo-single crystals in two-dimensional materials, characterized in that, include: A sample is provided, the sample comprising a flat substrate and a two-dimensional material layer located on the flat substrate; The two-dimensional material layer was observed using a dark-field microscope, and optical images of the two-dimensional material layer were obtained. The closed region in the optical image enclosed by a bright boundary line is taken as the target region; The target region is determined to be a true single crystal based on the consistent brightness observed within the target region. In response to different brightness levels within the target region, the target region is determined to be a pseudo-single crystal.

2. The method for identifying pseudo-single crystals of two-dimensional materials as described in claim 1, characterized in that, The pseudo-single crystal has a core-shell structure; the core-shell structure includes a core region and a shell region that surrounds the core region; the brightness of the core region is greater than the brightness of the shell region; the core region and the shell region have different electrical properties.

3. The method for identifying pseudo-single crystals of two-dimensional materials as described in claim 2, characterized in that, Also includes: The optical image is converted to grayscale; Calculate the average gray value of the core region and the shell region.

4. The method for identifying pseudo-single crystals of two-dimensional materials as described in claim 3, characterized in that, The average gray value of the core region is greater than the average gray value of the shell region; the scattering intensity of the core region is greater than the scattering intensity of the shell region.

5. The method for identifying pseudo-single crystals of two-dimensional materials as described in claim 2, characterized in that, The thickness of the pseudo-single crystal located in the core region is the same as the thickness of the pseudo-single crystal located in the shell region.

6. The method for identifying pseudo-single crystals of two-dimensional materials as described in claim 1, characterized in that, The process of observing the two-dimensional material layer using a dark-field microscope and acquiring an optical image of the two-dimensional material layer includes: The light source provides visible light as the incident light; The incident light rays enter the sample at an oblique angle from outside the objective lens of the dark field microscope, and the incident light rays illuminating the sample are scattered. The scattered light is collected using the optical information receiving device in the dark-field microscope, and converted into the optical image using the imaging device in the dark-field microscope.

7. The method for identifying pseudo-single crystals of two-dimensional materials as described in claim 6, characterized in that, The light source also provides white light, monochromatic light, yellow light, and red light as incident rays.

8. An electronic device, characterized in that, include: memory for storing computer programs; A processor for running the computer program to implement the method for identifying pseudo single crystals of two-dimensional materials as described in any one of claims 1 to 7; A display is used to output the processing results of the processor.

9. A storage medium storing program instructions, characterized in that, When the program instructions are executed, they implement the method for identifying pseudo single crystals of two-dimensional materials as described in any one of claims 1 to 7.

10. A system for identifying pseudo-single crystals in two-dimensional materials, characterized in that, include: The system includes 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 the optical images from the dark-field microscope and select true single crystals. The integrated circuit layout design module is configured to design two-dimensional devices and integrated circuits based on the true single crystals.

Images