CN109373918B - Efficient optical measurement method for two-dimensional material film thickness measurement - Google Patents
Efficient optical measurement method for two-dimensional material film thickness measurement Download PDFInfo
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Abstract
An efficient optical measurement method for measuring the thickness of a two-dimensional material film. Belongs to the technical field of color calculation and image processing based on thin film interference effect. The method comprises a color calculation process of the substrate and the two-dimensional material film to be measured with different thicknesses under the specified standard condition, and a subsequent calibration process of the actual imaging result based on the color calculation result as the standard under the specified standard condition. The method has the advantages of high efficiency, strong reliability and wide application range.
Description
Technical Field
The invention relates to the technical field of color calculation and image processing based on thin film interference effect, in particular to a high-efficiency optical measurement method for measuring the thickness of a two-dimensional material thin film.
Background
Various two-dimensional materials, such as graphene, hexagonal boron nitride, transition metal dichalcogenide represented by molybdenum disulfide and tungsten disulfide, black phosphorus, and the like, gradually enter the visual field of people due to excellent photoelectric and mechanical properties. The thickness of a two-dimensional material is closely related to its physical properties, so the thickness characterization of a two-dimensional material sample is the most important and common measurement item.
Currently, the most common two-dimensional methods for accurately characterizing the thickness of a material are atomic force microscopy and raman spectroscopy. However, these methods need to be improved because atomic force microscopy and raman spectroscopy are slow, inefficient, expensive and the sample has some sensitivity to the substrate.
Two-dimensional materials of different thickness on common substrates, e.g. SiO2On the/Si substrate, different colors can be obviously observed through an optical microscope, so that the thickness of the two-dimensional material can be represented by using the relation between the colors and the thickness of the two-dimensional material. Based on the theory, the two-dimensional material thickness measurement with the efficiency far higher than that of an atomic force microscope and a Raman spectrum can be completed only by using a common optical microscope with a digital camera. However, in actual practice, since the currently existing optical measurement method must be performed under the condition of fixing the illumination light source, the camera color matching function and other relevant parameter settings, these parameters are often different from measurement condition to measurement condition and difficult to determine; in addition, even if the color matching function of the light source and the camera can be determined, most digital cameras can automatically process images, so that external factors such as a fixed light source and the like become meaningless, and the existing optical measurement method is not suitable for all measurement conditions and is difficult to apply to actual experiments and production. The color of the substrate can be calculated in advance by considering the known thickness of the oxide coating layer, and can be calculated by referenceAnd calibrating the color of the whole image by the deviation of the actual color of the substrate to obtain an imaging result similar to that under the specified standard condition, and further applying the calibrated image to the thickness measurement of the two-dimensional material.
Disclosure of Invention
The invention aims to solve the problems of low efficiency of the conventional two-dimensional material film thickness measuring means and low reliability of the optical measuring method, and provides a high-efficiency optical measuring method for measuring the thickness of a two-dimensional material film.
A high-efficiency optical measurement method for measuring the thickness of a two-dimensional material film comprises a color calculation process of a substrate and the two-dimensional material film to be measured with different thicknesses under a specified standard condition, and a subsequent calibration process of an actual imaging result based on the color calculation result as a standard under the specified standard condition.
Preferably, the measuring method is realized by the following steps:
step one, specifying a standard condition, and taking a spectral power distribution of an illumination light source and a color matching function of a camera or an observer as fixed parameters under the standard condition;
calculating theoretical colors of the two-dimensional material film to be measured with corresponding different thicknesses through a reflectivity spectrum caused by film interference, and taking the theoretical colors as a substrate under a standard condition and with different thicknesses; converting the theoretical color from CIE XYZ color space to CIE Lab color space;
the method comprises the following steps of calculating theoretical colors of two-dimensional material films to be measured with different thicknesses through reflectivity spectra caused by film interference, and specifically comprises the following steps: obtaining corresponding theoretical colors in a CIE XYZ color space through the weighted summation of the spectral power distribution of the illumination light source as a fixed parameter and the integral or discrete value of the color matching function of a camera or an observer;
step three, solving the color difference between the color of the substrate in the CIE Lab color space and the color of the two-dimensional material film to be detected with different thicknesses, and taking the solved color difference as the distance between the color of the substrate and the color of the two-dimensional material film to be detected in the CIE Lab color space;
selecting a base part in an actual imaging color image of the two-dimensional material film to be detected, and calculating the average value of the color of the selected area in a CIE XYZ color space; selecting a base part in a color image obtained by actual optical microscope imaging through a flooding algorithm;
step five, calculating the color difference between the average value obtained in the step four and the theoretical color of the substrate in the CIE XYZ color space under the specified standard condition; bringing the color difference between the actual imaging image and the substrate under the specified standard condition into a calibration formula, calibrating the actual imaging image pixel by pixel through the calibration formula, and converting the image from CIE XYZ color space to CIE Lab color space;
and step six, comparing the color difference of the color of each pixel in the calibrated image in a CIE Lab color space and the average value of the substrate color in the calibrated image with the relation between the color difference and the thickness of the two-dimensional material film to be measured under the specified standard condition to obtain the thickness of the two-dimensional material film represented by the corresponding pixel color.
The invention has the beneficial effects that:
the high-efficiency optical measurement method for the thickness of the two-dimensional material film, provided by the invention, has the beneficial effects that:
1. the optical measurement method has the advantages of high efficiency and strong reliability;
2. the optical measurement method has wide application range, and can be directly applied to optical imaging images under the conditions of unknown and unfixed spectral power distribution of the illumination light source, color matching functions of a camera or an observer and other external parameters;
3. the optical measurement method has lower requirements on measurement equipment, is only a common optical microscope with a color digital camera, effectively controls the cost and realizes the practicability of the high-efficiency optical measurement method;
4. the optical measurement method of the invention has small calculation amount, thus being applicable to real-time measurement under real-time scanning.
5. In addition, compared with the traditional atomic force microscope and Raman spectroscopy, the efficient optical measurement method for the thickness of the two-dimensional material film provided by the invention has outstanding efficiency and cost advantages under the condition of realizing similar precision, thereby greatly facilitating the measurement of the thickness of the two-dimensional material film with large area and large scale and providing convenience for the accurate measurement of the thickness of the two-dimensional material film. Meanwhile, due to the fact that the calculated amount is small, the method can be applied to real-time measurement under real-time scanning, and on the premise that the thickness of a two-dimensional material film with the same area is measured, the method has the advantages of being obvious in efficiency, reliability and cost control.
Drawings
FIG. 1 is a model of a monolayer film of the present invention in two semi-infinite media.
FIG. 2 shows a 300nm SiO oxide layer according to the present invention2Actual original optical image of molybdenum disulfide film comprising 1-3 layers on a/Si substrate.
Fig. 3 is an image of the calibration conversion of fig. 2 according to the present invention.
Figure 4 is a graph of molybdenum disulfide film thickness before and after conversion and color difference between substrate and molybdenum disulfide for a given set of standard conditions in accordance with the present invention.
FIG. 5 is a flow chart of example 1 according to the present invention.
FIG. 6 shows a 300nm SiO oxide layer under the condition of D65 standard light source and CIE standard observer color matching function2Theoretical calculated value images of molybdenum disulfide films comprising 1-5 layers on a/Si substrate.
Fig. 7 is an image of the calibration conversion of fig. 6 according to the present invention.
FIG. 8 shows a 300nm oxide SiO film under the condition of color matching function between the A standard light source and MT9V032 CMOS (Edmund optics)2Theoretical calculated value images of molybdenum disulfide films comprising 1-5 layers on a/Si substrate.
Fig. 9 is an image of the calibration conversion of fig. 8 according to the present invention.
FIG. 10 is a graph of the color matching function of standard A light source and CIE standard observer using GrayWorld auto white balance algorithm for calibration at 300nm oxide SiO2Theoretical calculated value images of molybdenum disulfide films comprising 1-5 layers on a/Si substrate.
FIG. 11 is an image of the FIG. 10 calibration transform according to the present invention.
Figure 12 is a graph of molybdenum disulfide film thickness before conversion and substrate to molybdenum disulfide color difference for examples 2-4 of the present invention.
Figure 13 is a graph of molybdenum disulfide film thickness after conversion and substrate to molybdenum disulfide color difference for examples 2-4 of the present invention.
Fig. 14 is a flow diagram of the present invention.
Detailed Description
The first embodiment is as follows:
the efficient optical measurement method for measuring the thickness of the two-dimensional material film in the embodiment comprises a color calculation process of the substrate and the two-dimensional material film to be measured with different thicknesses under the specified standard condition, and a subsequent calibration process of an actual imaging result based on the color calculation result as a standard under the specified standard condition.
The second embodiment is as follows:
different from the first embodiment, the high-efficiency optical measurement method for measuring the thickness of the two-dimensional material film of the present embodiment includes:
step one, specifying a standard condition, and taking a spectral power distribution of an illumination light source and a color matching function of a camera or an observer as fixed parameters under the standard condition;
calculating theoretical colors of the two-dimensional material films to be measured with different thicknesses through a reflectivity spectrum caused by film interference, and taking the theoretical colors as the colors of the substrate under a standard condition and the colors of the two-dimensional material films with different thicknesses; converting the calculated theoretical color from CIE XYZ color space to CIE Lab color space; the two-dimensional material films with different layers are two-dimensional material films with different thicknesses;
the method comprises the following steps of calculating theoretical colors of two-dimensional material films to be measured with different thicknesses through reflectivity spectra caused by film interference, and specifically comprises the following steps: obtaining corresponding theoretical colors in a CIE XYZ color space through the weighted summation of the spectral power distribution of the illumination light source as a fixed parameter and the integral or discrete value of the color matching function of a camera or an observer;
step three, solving the color difference between the color of the substrate in the CIE Lab color space and the color of the two-dimensional material film to be detected with different thicknesses, and expressing the relation between the color difference and the thickness of the two-dimensional material film to be detected with different thicknesses by the color difference;
selecting a base part in an actual imaging color image of the two-dimensional material film to be detected, and calculating the average value of the color of the selected area in a CIE XYZ color space; selecting a base part in a color image obtained by actual optical microscope imaging through a flooding algorithm;
step five, calculating the color difference between the average value obtained in the step four and the theoretical color of the substrate in the CIE XYZ color space under the specified standard condition; bringing the color difference between the actual imaging image and the substrate under the specified standard condition into a calibration formula, calibrating the actual imaging image pixel by pixel through the calibration formula, and converting the calibrated actual imaging image from a CIE XYZ color space to a CIE Lab color space;
and step six, comparing the color difference of the color of each pixel in the calibrated actual imaging image in a CIE Lab color space and the average value of the substrate color in the calibrated image with the relation between the color difference and the thickness of the two-dimensional material film to be measured under the specified standard condition to obtain the thickness of the two-dimensional material film represented by the corresponding pixel color.
The third concrete implementation mode:
different from the second specific embodiment, in the first step, a standard condition is specified, and a color matching function between the spectral power distribution of the illumination light source and a camera or an observer is taken as a fixed parameter under the standard condition, wherein the specified standard condition refers to that a white light source and a camera are given as reference standards; the spectral power distribution of the illumination light source and the color matching function of the camera or the observer can be one of various white light sources and color matching functions;
the specific method for taking the spectral power distribution of the illumination light source and the color matching function of the camera or the observer as fixed parameters under the standard condition includes:
(since the color of the thin film material is primarily dependent on its overall reflectance for different wavelengths of visible light, the reflectance of the multilayer thin film interference system is a key parameter for model color calculations.)
First, the reflectance of the substrate was calculated from a model of a single-layer film in two semi-infinite media (as shown in fig. 1) by equation (1):
in the formula, there are the relations as formula (2), formula (3):
in the formulae (1), (2) and (3), λ is the wavelength of incident light, niIs the refractive index of the i-th layer medium, diIs the thickness of the i-th layer of dielectric, θiThe incident angle of the incident light to the i-th layer medium is, in general, θ is a normal incidence angle of the illumination light source of the optical microscopei＝0；
Then, the SiO of the oxide layer coating film with the known thickness is calculated2The refractive index of the two-dimensional material film on the Si substrate is shown as the formula (4):
the fourth concrete implementation mode:
different from the third specific embodiment, in the second step, the theoretical colors of the two-dimensional material films to be measured with different thicknesses are calculated through the reflectivity spectrum caused by film interference, and are used as the colors of the substrate under the standard condition and the colors of the two-dimensional material films with different thicknesses; and the process of converting the calculated theoretical color from the CIE XYZ color space to the CIE Lab color space specifically comprises the following steps:
firstly, calculating the color of a substrate and the theoretical color of the two-dimensional material film to be measured with different thicknesses under the specified standard condition:
in CIE XYZ color space, the theoretical color relationship of the two-dimensional material film to be measured with different thicknesses shown in formula (5) is as follows:
and normalizing the Y value by equation (6):
in the formulas (5) and (6), R (lambda) represents the reflectance as a function of the wavelength of visible light, I (lambda) is the spectral power distribution of the light source,
color matching functions for CIE standard observer;
then, selecting the color difference defined in the CIE Lab color space, and converting the theoretical color from the CIE XYZ color space to the CIE Lab color space through the function expression of the formulas (7) and (8) to obtain the CIE Lab color space coordinate value:
in the formula (I), the compound is shown in the specification,
Xn、Yn、Znis the CIE reference white point tristimulus value.
The fifth concrete implementation mode:
different from the fourth specific embodiment, in the third step, the process of obtaining the color difference between the color of the substrate in the CIE Lab color space and the color of the two-dimensional material film to be measured with different thicknesses and representing the relationship between the color difference and the thickness of the two-dimensional material film to be measured with different thicknesses includes:
after obtaining the coordinate value of the CIE Lab color space, calculating the color difference between the color of the substrate in the CIE Lab color space and the color of the two-dimensional material film to be measured with different thicknesses by using the formula (11):
in the formula (9), the reaction mixture is,
and
respectively the coordinates of the two-dimensional material film and the substrate in a CIE Lab color space; and (3) calculating CIELab color space coordinates of the two-dimensional material films with different thicknesses under the specified standard condition by using the formula (4) to the formula (9), wherein the obtained CIELab color space coordinates are the relation between the color difference and the thickness of the two-dimensional material films with different thicknesses under the specified standard condition, and the relation is used as a subsequent measurement standard.
The sixth specific implementation mode:
different from the fifth embodiment, in the fifth embodiment, the chromatic aberration between the average value obtained in the fourth step and the theoretical color of the substrate in the CIEXYZ color space under the specified standard condition is calculated; bringing the color difference between the actual imaging image and the substrate under the specified standard condition into a calibration formula, calibrating the actual imaging image pixel by pixel through the calibration formula, and converting the calibrated actual imaging image from a CIE XYZ color space to a CIE Lab color space, specifically:
(1) the process of calculating the color difference between the average value obtained in the fourth step and the theoretical color of the substrate in the CIE XYZ color space under the specified standard condition comprises the following steps:
for simplicity of expression, t ═ X Y Z is used]TRepresenting a vector comprising tristimulus values in the CIEXYZ space, such that the difference in average value from the theoretical color of the substrate in the CIEXYZ color space under the specified standard conditions is
Δt＝tspesub-trawsub(10)
In the formula (10), tspesubIs the tristimulus value vector, t, of the theoretical calculation of the substrate under given standard conditionsrawsubIs the average value of the tristimulus value vectors of the actual substrate in the original image;
(2) the process of calibrating the actual imaging image pixel by pixel through the calibration formula comprises the following steps:
first, to simplify the expression, expression (5) is expressed in a matrix form as a form of expression (11):
t＝ALr (11)
wherein t ═ X Y Z]TRepresenting a vector comprising CIEXYZ spatial tristimulus values, A being a matrix of 3 × N comprising a color matching function of a camera or an observer, N being the number of each discrete wavelength data within the visible range, L being a diagonal matrix containing spectral power distribution data of an illumination source, r being an N-dimensional vector containing reflectance spectral data of an observed object;
then, the original image is converted into an imaging result approximate to a given standard condition by equation (12):
trec＝traw+αJΔt (12)
in the formula (12), trecIs the vector of tristimulus values obtained after conversion, trawIs the tristimulus value vector of the original image to be converted, α J is a nonlinear transformation, which can be simplified to α J as 1, and Δ t is calculated by equation (10), and the original image is the original optical image obtained by the optical microscope.
The implementation case is as follows:
the materials, apparatus, methods and data used in the following examples are, unless otherwise specified, all materials, apparatus, methods and data conventional in the art and are commercially available and commercially available.
Example 1:
here, an oxide layer SiO of 300nm is selected2The actual optical image of a molybdenum disulfide film comprising 1-3 layers on a/Si substrate is shown in figure 2 as an example. Taking the color matching function of the standard light source A and the CIE standard observer as a given standard condition, an image approximating the given standard condition can be obtained by conversion, as shown in FIG. 3. The relationship between the thickness of the molybdenum disulfide film before and after conversion and given standard conditions and the color difference between the substrate and the molybdenum disulfide is shown in fig. 4. It can be seen that the conversion allows results that do not conform to the theoretical model to be approximated to the given conditions for accurate measurement of the thickness of the molybdenum disulfide film. The whole flow is shown in fig. 5.
Example 2:
the color matching function of a D65 standard light source and a CIE standard observer is selected, and SiO is formed on a 300nm oxide layer2Theoretical calculated value images for molybdenum disulfide films comprising 1-5 layers on a/Si substrate are shown in figure 6. Taking the color matching function of the standard light source a and the CIE standard observer as the given standard condition, an image approximating the given standard condition can be obtained by conversion, as shown in fig. 7. The relationship between the thickness of the molybdenum disulfide film before and after conversion and the color difference between the substrate and the molybdenum disulfide is shown in fig. 12 and 13.
Example 3:
the standard light source A and MT9V032 CMOS (Edmund optics) color matching function are selected to be used in the condition of 300nm oxide layer SiO2Theoretical calculated value images for molybdenum disulfide films comprising 1-5 layers on a/Si substrate are shown in figure 8. Taking the color matching function of the standard illuminant A and the color matching function of the standard observer CIE as a given standard condition, an image approximating the given standard condition can be obtained by conversion, as shown in FIG. 9. The relationship between the thickness of the molybdenum disulfide film before and after conversion and the color difference between the substrate and the molybdenum disulfide is shown in fig. 12 and 13.
Example 4:
a standard light source andcolor matching function of CIE standard observer, and using Gray World automatic white balance algorithm for calibration, at 300nm of oxide layer SiO2Theoretical calculated value images for molybdenum disulfide films comprising 1-5 layers on a/Si substrate are shown in figure 10. Taking the color matching function of the a standard light source and the CIE standard observer as the given standard condition, an image approximating the given standard condition can be obtained by conversion, as shown in fig. 11. The relationship between the thickness of the molybdenum disulfide film before and after conversion and the color difference between the substrate and the molybdenum disulfide is shown in fig. 12 and 13.
The present invention is capable of other embodiments and its several details are capable of modifications in various obvious respects, all without departing from the spirit and scope of the present invention.
Claims (3)
1. A high-efficiency optical measurement method for measuring the thickness of a two-dimensional material film is characterized by comprising the following steps: the method comprises the color calculation process of the substrate and the two-dimensional material film to be measured with different thicknesses under the specified standard condition, and the calibration process of the actual imaging result based on the color calculation result as the standard under the specified standard condition;
the measuring method comprises the following steps:
step one, specifying a standard condition, and taking a spectral power distribution of an illumination light source and a color matching function of a camera or an observer as fixed parameters under the standard condition;
calculating theoretical colors of the two-dimensional material films to be measured with different thicknesses through a reflectivity spectrum caused by film interference, and taking the theoretical colors as the colors of the substrate under a standard condition and the colors of the two-dimensional material films with different thicknesses; converting the calculated theoretical color from CIE XYZ color space to CIE Lab color space;
firstly, calculating the color of a substrate and the theoretical color of the two-dimensional material film to be measured with different thicknesses under the specified standard condition:
in the CIE XYZ color space, there is a relationship shown by equation (5):
and normalizing the Y value by equation (6):
in the formulas (5) and (6), R (lambda) represents the reflectance as a function of the wavelength of visible light, I (lambda) is the spectral power distribution of the light source,
color matching functions for CIE standard observer;
then, selecting the color difference defined in the CIE Lab color space, and converting the theoretical color from the CIE XYZ color space to the CIE Lab color space through the function expression of the formulas (7) and (8) to obtain the CIE Lab color space coordinate value:
in the formula (I), the compound is shown in the specification,
Xn、Yn、Znis the CIE reference white point tristimulus value
The method comprises the following steps of calculating theoretical colors of two-dimensional material films to be measured with different thicknesses through reflectivity spectra caused by film interference, and specifically comprises the following steps: obtaining corresponding theoretical colors in a CIE XYZ color space through the weighted summation of the spectral power distribution of the illumination light source as a fixed parameter and the integral or discrete value of the color matching function of a camera or an observer;
step three, solving the color difference between the color of the substrate in the CIE Lab color space and the color of the two-dimensional material film to be detected with different thicknesses, and expressing the relation between the color difference and the thickness of the two-dimensional material film to be detected with different thicknesses by the color difference;
selecting a base part in an actual imaging color image of the two-dimensional material film to be detected, and calculating the average value of the color of the selected area in a CIE XYZ color space; selecting a base part in a color image obtained by actual optical microscope imaging through a flooding algorithm;
step five, calculating the color difference between the average value obtained in the step four and the theoretical color of the substrate in the CIE XYZ color space under the specified standard condition; bringing the color difference between the actual imaging image and the substrate under the specified standard condition into a calibration formula, calibrating the actual imaging image pixel by pixel through the calibration formula, and converting the calibrated actual imaging image from CIE XYZ color space to CIELab color space;
(1) the process of calculating the color difference between the average value obtained in the fourth step and the theoretical color of the substrate in the CIE XYZ color space under the specified standard condition comprises the following steps:
for simplicity of expression, t ═ X Y Z is used]TRepresenting a vector comprising tristimulus values of the CIE XYZ space, such that the difference between the mean and the theoretical color of the substrate in the CIE XYZ color space under the specified standard conditions is
Δt＝tspesub-trawsub(10)
In the formula (10), tspesubIs the tristimulus value vector, t, of the theoretical calculation of the substrate under given standard conditionsrawsubIs the average value of the tristimulus value vectors of the actual substrate in the original image;
(2) the process of calibrating the actual imaging image pixel by pixel through the calibration formula comprises the following steps:
first, to simplify the expression, expression (5) is expressed in a matrix form as a form of expression (11):
t＝ALr (11)
wherein t ═ X Y Z]TRepresenting a vector comprising CIE XYZ spatial tristimulus values, A being a matrix of 3 × N, including color matching of a camera or observerA function; n is the number of each discrete wavelength data in the visible light range; l is a diagonal matrix containing spectral power distribution data of the illumination source; r is an N-dimensional vector containing the reflectance spectrum data of the observation object;
then, the original image is converted into an imaging result approximate to a given standard condition by equation (12):
trec＝traw+αJΔt (12)
in the formula (12), trecIs the vector of tristimulus values obtained after conversion, trawThe tristimulus value vector of the original image to be converted is obtained, α J is nonlinear transformation, the transformation is simplified into α J-1, and delta t is calculated by the formula (10);
and step six, comparing the color difference of the color of each pixel in the calibrated actual imaging image in a CIE Lab color space and the average value of the substrate color in the calibrated image with the relation between the color difference and the thickness of the two-dimensional material film to be measured under the specified standard condition to obtain the thickness of the two-dimensional material film represented by the corresponding pixel color.
2. A method for efficient optical measurement of thickness measurement of two-dimensional material films as claimed in claim 1, wherein: in the first step, a standard condition is specified, and a spectral power distribution of an illumination light source and a color matching function of a camera or an observer are used as fixed parameters under the standard condition, wherein the specified standard condition refers to that a light source and a camera are given as reference standards;
the specific method for taking the spectral power distribution of the illumination light source and the color matching function of the camera or the observer as fixed parameters under the standard condition includes:
first, the reflectance of the substrate was calculated from a model of a single-layer film in two semi-infinite media by equation (1):
in the formula, there are the relations as formula (2), formula (3):
in the formulae (1), (2) and (3), λ is the wavelength of incident light, niIs the refractive index of the i-th layer medium, diIs the thickness of the i-th layer of dielectric, θiThe incident angle of the incident light to the i-th layer medium is, in general, θ is a normal incidence angle of the illumination light source of the optical microscopei＝0；
Then, the SiO of the oxide layer coating film with the known thickness is calculated2The reflectivity of the two-dimensional material film on the Si substrate is shown as the formula (4):
3. a method for efficient optical measurement of thickness measurement of two-dimensional material films as claimed in claim 2, characterized in that: in the third step, the process of obtaining the color difference between the color of the substrate in the CIE Lab color space and the color of the two-dimensional material film to be measured with different thicknesses and expressing the relationship between the color difference and the thickness of the two-dimensional material film to be measured with different thicknesses is specifically as follows:
after obtaining the coordinate value of the CIE Lab color space, calculating the color difference between the color of the substrate in the CIE Lab color space and the color of the two-dimensional material film to be measured with different thicknesses by using the formula (9):
in the formula (9), the reaction mixture is,
and
respectively the coordinates of the two-dimensional material film and the substrate in a CIE Lab color space; and (3) calculating CIE Lab color space coordinates of the two-dimensional material films with different thicknesses under the specified standard condition by using the formula (4) to the formula (9), wherein the obtained CIE Lab color space coordinates are the relation between the color difference and the thickness of the two-dimensional material films with different thicknesses under the specified standard condition, and the relation is used as a subsequent measurement standard.
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| CN111999253A (en) * | 2020-06-19 | 2020-11-27 | 厦门虹鹭钨钼工业有限公司 | Qualitative detection method for fluorescent semiconductor compound nano material |
| CN113137930B (en) * | 2021-04-25 | 2022-02-01 | 西南石油大学 | Visual and quantitative determination method for thinning of foam liquid film |
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