Method for high-precision measurement of micro-nano structure charges based on electronic holography
By performing electron holographic experiments and phase gradient integration under electron microscope, the problem of insufficient resolution, accuracy and accuracy in charge measurement of micro-nano structures is solved, and high-precision measurement of a single basic charge unit is achieved.
Patent Information
- Application Number
- CN202510044576.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-12
- Publication Date
- 2025-04-11
AI Technical Summary
In the prior art, when measuring micro-nano structure charges, there are problems of insufficient resolution, accuracy and accuracy, and it is especially impossible to achieve direct measurement of a single basic charge unit.
Using an electron holography-based method, an electron holography experiment was performed under an electron microscope to obtain objects and reference holograms, the phase map was reconstructed using real-space reconstruction method, and the micro-nano structure charge was directly quantified by the contour integration of the phase gradient.
High-precision measurement of charge of micro-nano structures is achieved, and the measurement accuracy reaches a single basic charge unit, overcoming the problems of non-uniqueness and insufficient accuracy in traditional technology.
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Figure CN119805020A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of transmission electron microscopy technology, and in particular to a method for high-precision measurement of charges of micro-nano structures based on electron holography. Background Art
[0002] In the study of micro-nano structures and electrical properties of structures, traditional scanning probe microscopy (SPM) techniques, including single electron transistor scanning electrometer (SETSE) and scanning capacitance microscopy (SCM), have been widely used to detect and analyze charge distribution. These techniques usually rely on electric field response to measure the charge state of micro-nanoscale materials. For example, SETSE technology can achieve qualitative detection of charge at the nanoscale by scanning micro-nano structures and detecting changes in electric fields. However, the application of these methods also faces many limitations, which are mainly manifested in the following aspects: First, scanning probe microscopy has high requirements for the electrical boundary conditions of the sample, and it is necessary to ensure that the sample is in a suitable conductivity state and environmental conditions, and it is usually required to be measured in a high vacuum environment; second, although SETSE and SCM can reach the nanometer level in resolution, in actual measurement, the resolution and accuracy of these methods are limited by physical principles and instrument performance, especially when measuring complex or inhomogeneous structures, large errors may occur.
[0003] In contrast, electron microscopy has become an important tool for studying nanomaterials and structures due to its excellent spatial resolution. The phase image obtained by electron microscopy can directly reflect the potential distribution in the sample, so it has great application potential in theory. However, traditional electron microscopy charge measurement methods usually rely on indirect model fitting, which requires assumptions about the charge distribution and is calculated in combination with specific prior knowledge. For example, some studies assume that the charge distribution of micro-nano structures or samples conforms to a certain simple geometric shape, and then use fitting algorithms to infer the charge value. However, the limitation of this method is that it is non-unique, depends on the model and assumptions selected by the experimenter, and cannot directly reflect the actual charge distribution, which may introduce large measurement errors.
[0004] In recent years, off-axis electron holography has attracted widespread attention due to its ability to achieve high-precision measurement of potential distribution. By measuring the phase change of electron waves, off-axis electron holography can provide high-resolution information about the electric field and charge distribution. In this technique, after the electron beam penetrates the sample, the phase of its wave function changes, reflecting the potential distribution inside the sample. By reconstructing the phase image, researchers can accurately obtain the potential information of the nanostructure and indirectly infer the charge distribution. This method has great advantages, enabling potential measurement at the nanoscale and having higher spatial resolution than traditional scanning probe microscopy techniques. However, although off-axis electron holography has been successful in measuring the potential of a variety of materials and structures, existing research still has the following problems: First, although this method can provide potential information, it usually relies on indirect models and algorithms to infer the amount of charge, so it cannot directly quantify the charge, and the precision and accuracy are still subject to certain limitations; second, existing measurement methods cannot achieve the measurement accuracy of a single basic charge unit, which is crucial for studying the electrical properties of micro-nanostructures and nanostructures.
[0005] In summary, although traditional scanning probe microscopy and electron microscopy methods have certain applications in charge measurement, they still have limitations in terms of resolution, accuracy, and measurement precision. Especially when measuring the charge of micro-nano structures with high precision, the existing technology has not yet achieved direct measurement of a single elementary charge. In order to overcome these problems, researchers are in urgent need of a new technical method that can provide high resolution, low noise, and can directly measure the charge of a single micro-nano structure.
[0006] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention
[0007] The purpose of the present invention is to provide a method for high-precision measurement of the charge of micro-nano structures based on electron holography, thereby overcoming the problems of non-uniqueness and insufficient precision existing in traditional technologies.
[0008] To achieve the above object, the present invention provides a method for high-precision measurement of charge of micro-nano structures based on electron holography, comprising the following steps:
[0009] (1) Observe the sample under an electron microscope and obtain an electron holographic experimental image of the sample under the Lorentz mode. The sample is placed on the sample stage of the electron microscope, and a hologram of the sample area of interest is taken under the Lorentz mode to obtain an object hologram; and an empty hologram with the sample removed is taken to obtain a reference hologram;
[0010] (2) importing the two images into an image processing program, such as computer programming software, and reconstructing the phase image of the sample using the real space reconstruction method for the object hologram and the reference hologram;
[0011] (3) For the structural region of interest in the obtained phase image, the contour integration of the phase gradient is performed to obtain the total charge in the region surrounded by the integral contour. The method of the present invention can achieve quantitative measurement of micro-nanoscale high-precision charge.
[0012] Compared with the prior art, the present invention has the following beneficial effects:
[0013] (1) The present invention is based on a method for high-precision measurement of micro-nanostructure charge using electron holography. The electron holography experiment is carried out with transmission electron microscopes from various countries and a hologram of the sample area of interest is photographed to obtain an object hologram; an empty hologram with the sample removed is photographed to obtain a reference hologram; the hologram phase is reconstructed using the real space reconstruction method, which can improve the signal-to-noise ratio and resolution of the phase signal. Then, for the structure area of interest in the obtained phase map, the contour integration of the phase gradient is performed to obtain the total charge in the area surrounded by the integral contour.
[0014] (2) The method of the present invention overcomes the problems of non-uniqueness and insufficient precision existing in traditional technologies through innovative technical means. Specifically, the method of the present invention does not rely on the assumed charge distribution model, but directly integrates the phase gradient of the micro-nanostructure region to accurately quantify the charge in the region.
[0015] (3) The method of the present invention can achieve high-precision measurement of the charge of micro-nano structures, with the measurement accuracy reaching a single basic charge unit, thereby providing a more accurate electrical property analysis tool for nanoelectronics, nanomaterials and related fields. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 is an operation flow chart of a method for high-precision measurement of micro-nanostructure charge based on electron holography according to the present invention;
[0017] Figure 2 is a schematic diagram of electron holography based on transmission electron microscopy in the method according to the present invention;
[0018] Figure 3Schematic diagram of the charge measurement method of metal cobalt micro-nanostructure; (a) The simulated phase diagram of the metal cobalt micro-nanostructure, which only contains the contribution of the average internal potential energy; (b) The simulated phase diagram of the metal cobalt micro-nanostructure with a charge of 100; (c) The phase diagram obtained by subtracting Figure (b) from Figure (a) only reflects the contribution generated by 100 charges in the metal cobalt micro-nanostructure; (d) The accumulated charge (integration result) of the area indicated by the yellow box in Figure (c);
[0019] Figure 4 Schematic diagram of the charge measurement method of the silver nanoprobe: (a) The phase diagram of the silver nanoprobe, which only includes the contribution generated by the applied bias voltage; (b) The accumulated charge in the integration area (yellow box) of Figure (a). (c) The simulated phase diagram of the silver nanoprobe, which only includes the contribution generated by the applied bias voltage; (d) The accumulated charge in the integration area (yellow box) of Figure (c). DETAILED DESCRIPTION
[0020] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.
[0021] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.
[0022] like Figures 1 to 4 As shown, according to a specific embodiment of the present invention, a method for high-precision measurement of the charge of a micro-nano structure based on electron holography is described, and the specific detailed scheme is as follows:
[0023] Step 1: Observe the sample under an electron microscope and obtain an electron holographic experimental image of the sample under the Lorentz mode. The sample is placed on the sample stage of the electron microscope, and a hologram of the sample area of interest is taken under the Lorentz mode to obtain an object hologram; and an empty hologram with the sample removed is taken to obtain a reference hologram.
[0024] The thickness of the sample is less than 100 nm; the electron holographic spatial resolution of the electron microscope used is 2 nm (specifically referring to the general Lorentz electron microscope mode).
[0025] like Figure 2 The principle of electron holography is: the coherent electron waves emitted by the electron gun are divided into two beams, one beam propagates in a vacuum and is the reference wave, and the other beam penetrates the sample and propagates and is the object wave. Voltage is applied to the electrostatic holographic wire, so that the object wave and the reference wave are deflected in opposite directions and converge and interfere, thus forming an electron hologram on the image plane.
[0026] When the incident electron wave penetrates a thin sample, it is modulated by the electromagnetic potential of the sample and changes its amplitude and phase. The electron holography method based on electron microscopy records the amplitude and phase changes of the electron wave, thereby obtaining the electromagnetic potential field information of the sample. The distribution of the object wave function can be obtained by reconstructing the electron hologram.
[0027] As an implementation method, the phase image can be obtained as follows:
[0028] Step 2: Import the two images into an image processing program, such as computer programming software, and use the real-space reconstruction method to reconstruct the phase map of the sample from the object hologram and the reference hologram.
[0029] Step 3: For reference, Figure 3 The simulation schematic diagram is shown. The two phase images of the metal cobalt micro-nanostructure are subtracted to remove the influence of the average internal potential energy, thereby obtaining a phase image generated only by the charge. Figure 4 As shown in the figure, by subtracting the silver nanoprobe phase images obtained by applying different bias voltages, the influence of the average internal potential energy is removed, and finally a phase image contributed only by the charge is obtained. Then, the contour integration of the phase gradient is performed for the structural area of interest in the obtained phase image. For this purpose, a special computer program is compiled to realize the accurate contour integral calculation of the phase gradient, and then the total charge in the area surrounded by the integral contour is obtained.
[0030] The value of the charge is
[0031]
[0032] Among them, C E is a constant that depends on the electron energy, C is the integration area, is the integration contour (boundary of the integration region), is a two-dimensional gradient operator, is the phase, s is the curvilinear coordinate along the ring, n is the direction of the outer normal of the ring, and ds is the loop The phase map is imported into the program, and the contour integration of the phase gradient is performed on the structure area of interest in the obtained phase map, and then the total charge in the area surrounded by the integral contour is obtained.
[0033] The present invention proposes a method for high-precision measurement of the charge of micro-nano structures based on electron holography. The method overcomes the problems of non-uniqueness and insufficient precision existing in traditional technologies through innovative technical means. Specifically, the method of the present invention does not rely on the assumed charge distribution model, but directly quantifies the charge in the micro-nano structure region by integrating the phase gradient of the region. Through this method, we can achieve high-precision measurement of the charge of micro-nano structures, and the measurement accuracy reaches a single basic charge unit, thereby providing a more accurate electrical property analysis tool for nanoelectronics, nanomaterials and related fields.
[0034] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.
Claims
1. A method for high-precision measurement of charge of micro-nano structures based on electron holography, characterized in that: The following steps are involved: (1) Observe the sample under an electron microscope and obtain an electron holographic experimental image of the sample under the Lorentz mode. The sample is placed on the sample stage of the electron microscope, and a hologram of the sample area of interest is taken under the Lorentz mode to obtain an object hologram; and an empty hologram with the sample removed is taken to obtain a reference hologram; (2) importing the two images into an image processing program, such as computer programming software, and reconstructing the phase image of the sample using the real space reconstruction method for the object hologram and the reference hologram; (3) For the structural region of interest in the obtained phase image, the contour integration of the phase gradient is performed to obtain the total charge in the region surrounded by the integral contour. The method of the present invention can achieve quantitative measurement of micro-nanoscale high-precision charge.
2. The method for high-precision measurement of micro-nanostructure charge based on electron holography according to claim 1, characterized in that: The thickness of the sample is less than 100 nm.
3. The method for high-precision measurement of micro-nanostructure charge based on electron holography according to claim 1, characterized in that: The electron holographic spatial resolution of the transmission electron microscope used is 2 nm, specifically referring to the common Lorentz electron microscope mode.
4. The method for high-precision measurement of micro-nanostructure charge based on electron holography according to claim 1, characterized in that: The method of obtaining the sample electron hologram in step (1) comprises: placing the sample on the sample stage of the electron microscope, photographing the hologram of the sample area of interest in the Lorentz mode to obtain an object hologram; and photographing the empty hologram with the sample removed to obtain a reference hologram.
5. The method for high-precision measurement of micro-nanostructure charge based on electron holography according to claim 1, characterized in that: The method of obtaining the sample phase map in step (2) includes: importing the two images into an image processing program, such as computer programming software, and using the real space reconstruction method to reconstruct the sample phase map from the object hologram and the reference hologram.
6. The method for high-precision measurement of micro-nanostructure charge based on electron holography according to claim 1, characterized in that: The value of the charge in step (3) is as shown in formula (1): Among them, C E is a constant that depends on the electron energy, C is the integration area, is the integration contour (boundary of the integration region), is a two-dimensional gradient operator, is the phase, s is the curvilinear coordinate along the ring, n is the direction of the outer normal of the ring, and ds is the loop The phase map is imported into the program, and the contour integration of the phase gradient is performed on the structure area of interest in the obtained phase map, and then the total charge in the area surrounded by the integral contour is obtained.