Nanotechnologies—Measurement of the number of layers of graphene-related two-dimensional (2D) materials—Optical contrast method
Some standard content:
1CS17.180.30
CCSA50
National Standard of the People's Republic of China
GB/T 40071—2021
Nanotechnologies
Graphene-related two-dimensional materials
Layer measurement
Optical contrast method
Nanotechnologies-Measurement of the number of layers of graphenerelated two-dimensional (2D) materialsOptical contrast method2021-05-21Issued
State Administration for Market Regulation
National Standardization Administration
2021-12-01Implementation
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GB/T 400712021
This document is drafted in accordance with the provisions of GB/T1.12020% "Guidelines for standardization work - Part 1: Structure and drafting rules for standardization documents".
Please note that some contents of this document may involve patents: The issuing agency of this document does not assume the responsibility for identifying patents. This document is proposed by the Chinese Academy of Sciences.
This document is under the jurisdiction of the Nanomaterials Sub-Technical Committee of the National Nanotechnology Standardization Technical Committee (SA (/1C279/SC1)). The drafting units of this document are: Taizhou Juna New Energy Co., Ltd., Southeast University, Taizhou Graphene Research and Testing Platform Co., Ltd., Institute of Semiconductors, Chinese Academy of Sciences, Harbin Institute of Technology (Weihai), Metallurgical Engineering, China University of Science and Technology, China Academy of Sciences ... Shangye Information Standard Beach Research Institute, Jiangnan University, East China Normal University, Shenzhen University of Technology
The main drafters of this document: Ni Zhenhua, Liang Zheng, Ding Rong, Tan Pingheng, Tu Yingying, An Xuhong, Yu Yuanfang, Li Qian, Nan Haiyan, Wu Xing, Chen Liqiong.
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GB/T40071—2021
Graphene-related two-dimensional materials (carbon-based two-dimensional materials with a number of layers less than 10, including graphene, double-layer graphene, few-layer graphene, oxygen Graphene (such as graphene) has excellent electrical, optical, mechanical, thermal and other properties, which has aroused widespread interest in academia and industry. The number of layers of graphene-related two-dimensional materials is a key parameter affecting the performance of the material. Accurately measuring the number of layers is the core issue of research, development and application of graphene-related two-dimensional materials. As a fast, non-destructive and highly sensitive measurement method, the optical contrast method has been widely used to measure the number of layers of graphene-related two-dimensional materials such as graphene, double-layer graphene and few-layer graphene. In the process of measuring the number of layers using the optical contrast method, the measurement results will be affected by the thickness of the silicon (Si) substrate surface dixenon (Si), the numerical aperture of the microscope objective, the data processing method and other test conditions, which need to be standardized. rrkaeerkAca
Nanotechnology Optical contrast method for measuring the number of layers of graphene-related two-dimensional materials
GB/T40071—2021
Warning: Personnel using this document should have practical experience in formal laboratory work. This document does not point out all possible safety issues. Some test processes specified in this document may lead to dangerous situations. Users are responsible for taking appropriate safety and health measures and ensuring that the conditions specified in relevant national laws and regulations are met. 1 Scope
This document specifies the instruments, equipment, sample preparation, measurement procedures, test reports, etc. for measuring the number of layers of graphene-related two-dimensional materials using the optical contrast method (including reflectance spectroscopy and optical imaging). This document is applicable to the layer number measurement of graphene flakes and graphene films with high crystal quality, lateral dimensions of not less than 2 μm, and not more than 5 layers produced by mechanical exfoliation or chemical vapor deposition (CVD). Graphene flakes and graphene films produced by other methods can refer to this article 2 Normative references
The contents of the following documents constitute the essential clauses of this document through normative references in the text. Among them, for references with a date, only the version corresponding to that date applies to this document; for references without a date, the latest version (including all amendments) applies to this document GB/T30544.13 Nanotechnology Terminology Part 13: Graphene and Related Dimensional Materials 3 Terms and Definitions
The terms and definitions defined in GB/T30544.13 and the following terms and definitions apply to this document. 3.1|| tt||Graphene-related 2D material;GR2M Carbon benzene 2D material with no more than 10 layers
Note: including graphene, double-layer graphene, few-layer right graphene, graphene oxide, etc. 3.2
Graphene flake
Graphene nanoplatelet graphene nanoplatelet; graphene nanoplatelet GNP Nanoplatelet composed of graphene layers,
Note : Common order is less than 3nm, horizontal size range is about 100nm to 100)mm [Source: G3/T30541.13-20[8.3.1.2.1[, modified 3.3
graphene film graphene film
Nano-thin sheet composed of graphene layers.
Note 1: Common thickness is less than 3nm
Note 2: Compared with graphene flakes (3.2), the right graphene film (3.3) has a larger extension in length and width 3.4
Number of layers of layers
《Two-dimensional materials）The number of layers that make up the two-dimensional material. 1
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GB/T 40071—2021
Optical contrast valueopticalcontrastvalueThe relative difference between the reflected light intensity of the blank substrate area of the two-dimensional material and the reflected light intensity of the sample area on the substrate, expressed as the formula ()
I warne
Igielraue
eoulhe-rats
In the formula:
Optical contrast value;
Reflected light intensity of the blank substrate area;
Reflected light intensity of the sample area.
Note: The sample on the substrate is usually a nanosheet [e.g., graphene flakes (3.2) or a nanosheet [e.g., graphene film (3.3)]. 3.6
G channel contrast value
Green channel contrast value
G channel contrast value
(Two-dimensional materials) The optical contrast value (3.5) is expressed by the difference between the (G channel value) of the blank substrate area in the optical micrograph and the (G channel value) of the area outside the substrate sample, see formula (2) C
Where:
Gruinuate
G channel contrast value:
GoutitreGouipte
Ganhestran
Blank substrate area in the optical micrograph Channel value of the domain: (channel value of the area where the sample is located in the optical microscope image. Note 1: The sample on the substrate is usually a right graphene sheet (3,2) or a graphene thin mold (3.3). (2)
Note 2: The wavelength range corresponding to the red channel (ruler channel) is about 590nm~720nm. The wavelength range corresponding to the green channel (G channel) is about 520mm~590nm, and the wavelength range corresponding to the monitoring channel (B channel) is about 435nm~~520nm. 3.7
Optical contrast method|| tt||opticalconirastmethod
<Two-dimensional materials) A method for determining the number of layers (3.4) of nanosheets or nanothin sheets on a specific substrate using optical contrast values (3.5). 4 Principle
4.1 Theoretical basis
As shown in Figure 1a), (from top to bottom) a multilayer film structure is formed by graphene sheets or graphene films, SiO_ layers, and Si layers: Due to the light absorption of the two-dimensional material itself and the influence of the interference effect of the multilayer film, Iul and Ir exist The difference is calculated by formula (1) to estimate the optical contrast between the substrate and the sample (, and the theoretical and experimental results show that when the number of layers of graphene sheets or graphene films is different, ( is also different, and there is a one-to-one correspondence between the number of layers and (, so ( can be used to determine the number of layers of graphene sheets or graphene films.
Theoretically, the optical contrast method can be used under different incident light wavelengths. When the incident light is a continuous wavelength of the gate light, the intensity of the reflected light depends on the wavelength. Assume that the reflected light intensity when the wavelength is 1 (λ),According to formula (3), C(a)
is the optical contrast value when the wavelength is 1. When the wavelength takes a series of continuous values, it is also called optical contrast -rKaeerKa-
Iotlbots.e(a)
Iample()
degree spectrum;
GB/T40071—2021
When the wavelength is, the reflected light intensity of the blank substrate area. When the wavelength takes a series of continuous values, Iute(a) is also called the reflectance spectrum of the substrate;
When the wavelength is, the reflected light intensity of the sample area. When the wavelength takes a series of continuous values, Iile() is also called the reflectance spectrum of the sample
foelaae
ho2'zc223||tt ||for*f12/23+
Multilayer film incident, reflection and transmission model
Silicon dioxide
-0:1400500600
Wavelength/nm
Theoretical optical contrast ratio of graphene sheets or graphene films with different numbers of layers
Figure 1 Schematic diagram of the principle of optical contrast method
4.2 Measurement principle of commonly used optical contrast method 4.2.1 Reflection spectroscopy
Figure 1b) shows the theoretically calculated optical contrast spectrum C (a) of graphene sheets or graphene films with different numbers of layers on 300nmSi03/Si substrate, where the wavelength range used is 400nm800nm, and the wavelength ranges corresponding to the B, G, and R channels of the optical microscope image are marked with blue, green, and red areas, respectively. From Figure 1b), we can see that: a) The optical contrast spectra (>) corresponding to graphene flakes or graphene films with different numbers of layers are different. When the wavelength λ is the same, the more layers there are, the larger C(a) is:
The optical contrast spectrum C() corresponding to different numbers of layers has: peaks (maximum) in the visible light wavelength range (approximately 435nm~720nm), and the peak value is recorded as C, and the corresponding wavelength value of C is recorded as λ. c) The difference between the optical contrast peak values C corresponding to different numbers of layers is the largest. It is most suitable for determining the number of layers of the sample. Therefore, C can be used to measure the number of layers of graphene sheets or graphene films. 4.2.2 Optical image method
As shown in Figure 1b), when the number of layers of graphene sheets or graphene films is 15, although there are some differences in the values of each white, they are all in the G channel of the optical microscope image. Therefore, Iaul (a) and Ixlraue (λ,) can also be replaced by the G channel values Gsl and Gxrate respectively, and the G channel contrast value C between the sample and the substrate can be obtained using formula (2). The theoretical value of the G channel contrast value is the integrated average value of the optical contrast spectrum in the wavelength range corresponding to the channel. As shown in Figure 1b), the values of the number of layers of graphene sheets or graphene films are different, and there is a one-to-one correspondence between the number of layers and C. Therefore, C can also be used to measure the number of layers of graphene sheets or graphene films. It should be noted that before using the optical image method to measure the number of layers, a G channel contrast detection layer number correspondence table is first established based on samples with known number of layers (as shown in Table 2). After establishing this table, under the same test conditions, the optical image method can be used to quickly and accurately measure the number of layers. 5 Instruments and equipment 5.1 Microspectrometer: used for reflection spectroscopy, including grating spectrometer and optical microscope. It has the function of reflection spectrum measurement. In GB/T 40071-2021, the scanning range of the spectrometer is 400nm~800nm, and the spectral resolution is better than 2nm. Before measurement, the micro-spectrometer should be calibrated according to the relevant technical specifications, and tested according to the relevant test specifications. 5.2 Optical microscope: Use the optical imaging method, equipped with a white light source (such as a halogen lamp or a fluorine lamp), a 100x objective lens (numerical aperture not less than 0.8), and the observation mode is bright field; including a digital camera, color imaging, and its pixel is better than 100,000. 6 Sample preparation
6.1 The substrate used in this document should be a Si substrate with a 300nm/5nm thick SiO2 layer on the surface (hereinafter referred to as 300nmSiO2/Si substrate) Www.bzxZ.net
6.2 For graphene flake samples mechanically peeled from 300nmSiO2/Si substrate, they can be used directly without further treatment. 6.3 For graphene film samples prepared by (CVD), the sample needs to be transferred to a 300nmSiO2/Si substrate (for specific steps, please refer to Appendix A)
6.4 Observe the sample under a microscope, and there should be no obvious impurities in the test area. 7 Measurement steps
Reflection spectroscopy measurement steps
7.1.1 Select the measurement area
Observe the sample using an optical microscope and determine the sample measurement area. This area should include both the blank substrate and the sample. 7.1.2 Collect the reflection spectrum
7.1.2.1 Focus the measurement area to observe the clear edge of the graphene sheet or film. 7.1.2.2 Measure the reflectance spectrum of the substrate, with a wavelength scanning range of 400nm~800nm, and adjust the incident light intensity or integration time so that the signal light intensity at a wavelength of 570nm is 10 times or more of the background signal (i.e., the signal under a dark environment). 7.1.2.3 Under the same observation conditions, collect the reflectance spectra Ihrmate() and 1amg(a) of the substrate and sample in turn. Among them, 5 positions are randomly selected for collection in the area where the substrate sample is located. Get "m()", ". () where one of them is [~5. 7.1.3 Obtain the optical contrast spectrum
According to formula (3). From the reflectance spectra Itzr() of the substrate and sample. I(r(a), obtain the optical contrast spectrum C() (a) where i=1~5,
7.1.4 Obtain Get the peak value of the optical contrast spectrum
Take the arithmetic mean of the peak values of the 5 optical contrast spectra C() (>). See formula (4). Calculate the peak value of the optical contrast spectrum of the sample C (retain to 2 decimal places):
Where:
C0)()The peak value, where -[-5.
Note that the deviation between a single measured value and the arithmetic mean value cannot be greater than 10%, otherwise re-measure. At the same time, if the wavelength value corresponding to C is 600nm, this method should not be used to measure the number of layers. 7.1.5 Determine the number of sample layers
According to the peak value C of the optical contrast spectrum of Yi 1. Mountain, the number of sample layers is obtained. rKaeerkAca-
CReference range
0.062C,0.17
0.173G 30.26
0.26-C,0.34
0.34-C0.40
0.40-60.46
7.1.6 Test samples
For test samples, please refer to Appendix 13.
Measurement steps of optical image method
Table 1 Optical contrast spectrum peak C—
.Typical value
One layer corresponding relationship
7.2.1 Select samples with known number of layers to establish the corresponding relationship table of G channel contrast value C—number of layers GB/T 40071—2021
7.2.1.1 Select the three samples prepared by mechanical separation method with known number of layers (n=1.2.3, 4, 5, 6 in H). Refer to Chapter 6 for sample preparation process. For n=1.2, 3, 4.5, 6, repeat steps 7.2.1.4~7.2.1.7 respectively. 7.2.1.2 Place a standard plate under the 100x objective lens, focus and perform balance calibration. 7.2.1.3 Select a blank substrate area without sample coverage, adjust the gamma value of the digital camera image processing software, so that the color of the image is basically the same as the color seen by the microscope (the difference in gamma estimation will lead to the difference in contrast detection. Do not change it after adjustment). Then adjust the brightness so that the gray value of the image is 125~1357. 2.1.4 Select the measurement area according to 7.1.1. 7.2.1.5 The steps for taking optical images are as follows: a)
Ensure that the sample to be measured is in the center of the observation window and focus the measurement area to observe the clear edge of the graphene sheet or film. Take 1 optical microscopic image of the sample. h) Under the same observation and shooting conditions (including gamma value, light intensity, integration time, focus, pixels, etc.), take 3 optical microscopic images on three different empty substrate areas without sample coverage. 7.2.1.6
The steps to obtain the G channel contrast value image are as follows: extract the channel values of each pixel point of the three substrate optical micrographs and the sample optical micrograph respectively, a)
b) for substrate D, the G channel value of each pixel point is obtained by averaging the G channel values of the same position in the three substrate optical micrographs.
For each pixel point of Liu, calculate its G channel contrast value according to formula (2) to obtain the G channel contrast value image. The steps to obtain the typical value of (channel contrast) of the sample with a known number of layers are as follows: 7.2.1.7
In the G channel contrast value image obtained in 7.2.1.6), randomly select 5 positions in the sample area to obtain 5 G channel contrast values and calculate their arithmetic mean (the deviation between a single measured value and the average value should not be less than 10%). This value is the G channel contrast estimate of the sample with a known number of layers. For 3 samples with the same number of layers n, their G channel contrast estimates are recorded as Cs(n), Cs(n) (n), and Cs(n) respectively.
b) Calculate the arithmetic mean of C(n), C(n), and C(n). Obtain A. "A is the typical value of the G channel contrast value Cc of the sample with n layers (retained to 2 decimal places): Note that the deviation between a single measured value and the arithmetic mean should not be greater than 10%, otherwise the measurement should be repeated.
7.2.1.8 Use A1, A2, and A6 to establish the G channel contrast value Cr-rrKaeerKAca-
layer number correspondence table (see Table 2).
GB/T 40071—2021
Table 2 G channel contrast value C.
C reference range
0.5XA1C:A1|0.5X(A2-A1)
A2—C.5X(A2-A1)CaA20.5X(A3-A2)A3-0.5X(A3-A2)≤CA3
A4 0.5X(A4 A3)-CGA4
0.5X(A4 A3)
A5 0,5X(A3 A4)CGA5-0.5X(A6A5)Determine the number of layers of unknown samples
Corresponding relationship of the number of layers
C.Typical value
Ensure that the optical microscope observation conditions and shooting conditions are the same as those in 7.2.1. Select the measurement area according to 7.2.1.4.
According to 7.2.1.5,
7.2.2.4According to 7.2.1.6, obtain the G channel contrast value image: 7.2.2.5 Obtain the G channel contrast of the unknown sample, number of layers
Randomly select 5 positions in the sample area to be tested in the (channel contrast value image) to obtain 5 (channel contrast detection C8), where; 1~5. According to the following formula (5), the arithmetic mean Cc is obtained (retained to 2 decimal places). The deviation between a single measurement value and the arithmetic mean should not be greater than 10%. Otherwise, re-measure in reverse order....(5 )
Refer to Table 2 and obtain the number of layers of the sample to be tested according to the reference range. 7.2.3 Test samples
For details of the test samples, please refer to Appendix C.
8 Test report
The test report should include the following information:
Test period:
Test number:
Measurer;
Source and information of the sample;
Measurement method;
Type, brand and model of the test instrument; If the number of layers is measured by the base optical image method, the "G channel contrast value Cc test result" should be attached;
Error analysis when necessary.
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Number of layers corresponding relationship" table:
Appendix A
(Informative)
GB/T 40071—2021
Sample transfer operation example: CVI growth copper-based graphene film sample transfer operation steps A.1 Spin-coat a drop of polymethylmethacrylate (PMMA) at 300 rpm onto the surface of the CVD-grown copper-based graphene film sample (i.e., GR2M/Cu/GR2M multilayer film) to form a PMMA/GR2M/Cu/GR2M multilayer film structure, where PMMA is the transfer support layer and R2M refers to single-layer, double-layer, or few-layer graphene. A.2 Use 0.5 mol/L ammonium persulfate (VH,S,O) solution to slightly corrode the Cu substrate of the sample and repeatedly clean it with ultrapure water. In this process, the PMMA/GR2M/Cu/GR2M multilayer film structure will float on the surface of (NII)SO, solution, the bottom Cu/GR2M layer will be dissolved, and the top PMMA/GR2M layer will remain unreacted. Thus, the GR2M at the bottom of Cu can be removed to obtain a PMMA/GR2M/Cu structure. The body corrosion and cleaning steps are: a) float in (NH,)SO. solution for 3 minutes, and then float in ultrapure water for 5 minutes: b) Repeat step a) 3 to 5 times.
A.3 Use (NII)SO, solution to completely etch away the Cu layer to obtain a PMMA/CR2M multilayer film structure. The processing time of this step depends on the thickness of Cu and the concentration of (NII)SO. For example, the corrosion time of 25um thick Cu in 0.5mol/L (NII)SO: solution is about 2 hours
A.4: float in ultrapure water for 30 minutes (this step can be performed multiple times). Each ultrapure water bath should be prepared in a separate container. A.5 Use 300nmSiO./Si substrate to pick up the PMMA/GR2M sample floating on the ultrapure water surface: Place it on a heating plate at 80℃ for 10 minutes to remove moisture, then place it on a heating plate at 180℃ for 15 minutes to relax the PMMA film, A.6 Soak PMMA/GR2M/300nmSiO./Si in ketone towel. Let it stand for 10 hours to dissolve the PMMA layer, then place GR2M/300nm SiO2/Si is sequentially placed in anhydrous ethanol and ultrapure water and soaked for 10 minutes each. After taking it out, it is blown with high-purity nitrogen for ten minutes to obtain a clean GR2M/300nmSi)/Si sample.
A.7 If the sample surface is not clean after the above steps, appropriately extend the time and number of corrosion or ultrapure water cleaning, or use 50°C acetone to dissolve the PMMA layer: the following steps are for reference: a) Increase or decrease the concentration of (VII).SO: solution to increase or decrease the corrosion rate. Low corrosion rate is beneficial to maintain the integrity of the sample during the corrosion process.
h) Select other etching solutions, such as FcCl, solution, etc. c): Select other organic materials as the transfer support layer, such as polydimethylsiloxane (PDMS for short), etc.: d) Use oxygen (O,) plasma to treat the back side of the PMMA/GR2M/Cu/GR2M multilayer structure. The etching time is 3min~5min. Etch away the GR2M at the bottom of Cu, and then proceed to A2 and subsequent steps: This method can appropriately reduce the number of (VH), S.0. solution etching and ultrapure water cleaning in step A.2. A.8 (VI) The optical pictures taken after the transfer of the grown copper-based graphene film are shown in Figures A and I. 7
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GB/T 40071—2021
Graphene
Optical pictures taken after the transfer of CVD-grown copper-based graphene film (substrate is 300nmSi0)2/Si) (Example) Figure A.1
rrKaeerkAca-A2, A6 establish the corresponding relationship table of G channel contrast value Cr-rrKaeerKAca-
layer number (see Table 2).
GB/T 40071—2021
Table 2G channel contrast value C.
C reference range
0.5XA1C:A1|0.5X(A2-A1)
A2—C.5X(A2-A1)CaA20.5X(A3-A2)A3-0.5X(A3-A2)≤CA3
A4 0.5X(A4 A3)-CGA4
0.5X(A4 A3)
A5 0,5X(A3 A4)CGA5-0.5X(A6A5) Determine the number of layers of unknown samples
Corresponding relationship of the number of layers
C. Typical value
Ensure that the optical microscope observation conditions and shooting conditions are the same as the observation conditions in 7.2.1. Select the measurement area according to 7.2.1.4.
According to 7.2.1.5, take optical pictures.
7.2.2.4According to 7.2.1.6, obtain the G channel contrast value image: 7.2.2.5 Obtain the G channel contrast of the unknown sample. Number of layers
Randomly select 5 positions in the sample area to be measured in the (channel contrast value image) to obtain 5 (channel contrast detection C8), where; = 1~5. According to the following formula (5), the arithmetic mean Cc is obtained (retained to 2 decimal places). The deviation between a single measurement value and the arithmetic mean should not be greater than 10%. Otherwise, re-measure in reverse order. ....(5 )
Refer to Table 2 and obtain the number of layers of the sample to be tested according to the reference range. 7.2.3 Test samples
For details of the test samples, please refer to Appendix C.
8 Test report
The test report should include the following information:
Test period:
Test number:
Measurer;
Source and information of the sample;
Measurement method;
Type, brand and model of the test instrument; If the number of layers is measured by the base optical image method, the "G channel contrast value Cc test result" should be attached;
Error analysis when necessary.
-rrKaeerKa-
Number of layers corresponding relationship" table:
Appendix A
(Informative)
GB/T 40071—2021
Sample transfer operation example: CVI growth copper-based graphene film sample transfer operation steps A.1 Spin-coat a drop of polymethylmethacrylate (PMMA) at a speed of 3000/min onto the surface of the CVD-grown copper-based graphene film sample (i.e., GR2M/Cu/GR2M multilayer film). Form a PMMA/GR2M/Cu/GR2M multilayer film structure, where PMMA is the transfer support layer, R2M refers to a single layer, double layer, or few layers. Graphene. A.2 Use 0.5mol/L ammonium persulfate (NH4SO4) solution to slightly etch the Cu substrate of the sample, and then wash it repeatedly with ultrapure water. During this process, the PMMA/GR2M/Cu/GR2M multilayer film structure will float on the surface of the (NH4SO4) solution, the bottom Cu/GR2M layer will be dissolved, and the top PMMA/GR2M layer will remain unreacted. Thus, the GR2M at the bottom of Cu can be removed to obtain the PMMA/GR2M/Cu structure. The body corrosion and cleaning steps are: a) Float in (NH4SO4) solution for 3 minutes, then float in ultrapure water for 5 minutes: b) Repeat step a) 3~-5 times.
A.3 Use (NII)SO solution to completely etch away the Cu layer. Get a PMMA/CR2M multilayer film structure. The processing time of this step depends on the thickness of Cu and the concentration of (NII)SO. For example, the corrosion time of 25um thick Cu in 0.5mol/L (NII)SO solution is about 2 h
A.4: Float in ultrapure water for 30 minutes (this step can be performed multiple times). Each ultrapure water bath should be prepared in a separate container. A.5 Use 300nmSiO./Si substrate to pick up the PMMA/GR2M sample floating on the ultrapure water surface: Place H on a heating plate at 80℃ for 10 minutes to remove moisture, then place it on a heating plate at 180℃ for 15 minutes to relax the PMMA film, A.6 Soak PMMA/GR2M/300nmSiO./Si in ketone. Let it stand for 10 hours to dissolve the PMMA layer, then place GR2M/300nm SiO2/Si is sequentially placed in anhydrous ethanol and ultrapure water and soaked for 10 minutes each. After taking it out, it is blown with high-purity nitrogen for ten minutes to obtain a clean GR2M/300nmSi)/Si sample.
A.7 If the sample surface is not clean after the above steps, appropriately extend the time and number of corrosion or ultrapure water cleaning, or use 50°C acetone to dissolve the PMMA layer: the following steps are for reference: a) Increase or decrease the concentration of (VII).SO: solution to increase or decrease the corrosion rate. Low corrosion rate is beneficial to maintain the integrity of the sample during the corrosion process.
h) Select other etching solutions, such as FcCl, solution, etc. c): Select other organic materials as the transfer support layer, such as polydimethylsiloxane (PDMS for short): d) Use oxygen (O,) plasma to treat the back side of the PMMA/GR2M/Cu/GR2M multilayer structure. The etching time is 3min~5min. Etch away the GR2M at the bottom of Cu, and then proceed to A2 and subsequent steps: This method can appropriately reduce the number of (VH), S.0. solution etching and ultrapure water cleaning in step A.2. A.8 (VI) The optical images taken after the transfer of the grown copper-based graphene film are shown in Figures A and I. 7
-riKaeerkAca-
GB/T 40071—2021
Graphene
Optical images taken after the transfer of CVD-grown copper-based graphene film (substrate is 300nmSi0)2/Si) (Example) Figure A.1
rrKaeerkAca-A2, A6 establish the corresponding relationship table of G channel contrast value Cr-rrKaeerKAca-
layer number (see Table 2).
GB/T 40071—2021
Table 2G channel contrast value C.
C reference range
0.5XA1C:A1|0.5X(A2-A1)
A2—C.5X(A2-A1)CaA20.5X(A3-A2)A3-0.5X(A3-A2)≤CA3
A4 0.5X(A4 A3)-CGA4
0.5X(A4 A3)
A5 0,5X(A3 A4)CGA5-0.5X(A6A5) Determine the number of layers of unknown samples
Corresponding relationship of the number of layers
C. Typical value
Ensure that the optical microscope observation conditions and shooting conditions are the same as the observation conditions in 7.2.1. Select the measurement area according to 7.2.1.4.
According to 7.2.1.5, take optical pictures.
7.2.2.4According to 7.2.1.6, obtain the G channel contrast value image: 7.2.2.5 Obtain the G channel contrast of the unknown sample. Number of layers
Randomly select 5 positions in the sample area to be measured in the (channel contrast value image) to obtain 5 (channel contrast detection C8), where; = 1~5. According to the following formula (5), the arithmetic mean Cc is obtained (retained to 2 decimal places). The deviation between a single measurement value and the arithmetic mean should not be greater than 10%. Otherwise, re-measure in reverse order. ....(5 )
Refer to Table 2 and obtain the number of layers of the sample to be tested according to the reference range. 7.2.3 Test samples
For details of the test samples, please refer to Appendix C.
8 Test report
The test report should include the following information:
Test period:
Test number:
Measurer;
Source and information of the sample;
Measurement method;
Type, brand and model of the test instrument; If the number of layers is measured by the base optical image method, the "G channel contrast value Cc test result" should be attached;
Error analysis when necessary.
-rrKaeerKa-
Number of layers corresponding relationship" table:
Appendix A
(Informative)
GB/T 40071—2021
Sample transfer operation example: CVI growth copper-based graphene film sample transfer operation steps A.1 Spin-coat a drop of polymethylmethacrylate (PMMA) at a speed of 3000/min onto the surface of the CVD-grown copper-based graphene film sample (i.e., GR2M/Cu/GR2M multilayer film). Form a PMMA/GR2M/Cu/GR2M multilayer film structure, where PMMA is the transfer support layer, R2M refers to a single layer, double layer, or few layers. Graphene. A.2 Use 0.5mol/L ammonium persulfate (NH4SO4) solution to slightly etch the Cu substrate of the sample, and then wash it repeatedly with ultrapure water. During this process, the PMMA/GR2M/Cu/GR2M multilayer film structure will float on the surface of the (NH4SO4) solution, the bottom Cu/GR2M layer will be dissolved, and the top PMMA/GR2M layer will remain unreacted. Thus, the GR2M at the bottom of Cu can be removed to obtain the PMMA/GR2M/Cu structure. The body corrosion and cleaning steps are: a) Float in (NH4SO4) solution for 3min, then float in ultrapure water for 5min: b) Repeat step a) 3~-5 times.
A.3 Use (NII)SO solution to completely etch away the Cu layer. Get a PMMA/CR2M multilayer film structure. The processing time of this step depends on the thickness of Cu and the concentration of (NII)SO. For example, the corrosion time of 25um thick Cu in 0.5mol/L (NII)SO solution is about 2 h
A.4: Float in ultrapure water for 30 minutes (this step can be performed multiple times). Each ultrapure water bath should be prepared in a separate container. A.5 Use 300nmSiO./Si substrate to pick up the PMMA/GR2M sample floating on the ultrapure water surface: Place H on a heating plate at 80℃ for 10 minutes to remove moisture, then place it on a heating plate at 180℃ for 15 minutes to relax the PMMA film, A.6 Soak PMMA/GR2M/300nmSiO./Si in ketone. Let it stand for 10 hours to dissolve the PMMA layer, then place GR2M/300nm SiO2/Si is sequentially placed in anhydrous ethanol and ultrapure water and soaked for 10 minutes each. After taking it out, it is blown with high-purity nitrogen for ten minutes to obtain a clean GR2M/300nmSi)/Si sample.
A.7 If the sample surface is not clean after the above steps, appropriately extend the time and number of corrosion or ultrapure water cleaning, or use 50°C acetone to dissolve the PMMA layer: the following steps are for reference: a) Increase or decrease the concentration of (VII).SO: solution to increase or decrease the corrosion rate. A low corrosion rate is beneficial to maintaining the integrity of the sample during the corrosion process.
h) Select other etching solutions, such as FcCl, solution, etc. c): Select other organic substances as transfer support layers, such as polydimethylsiloxane (PDMS for short): d) Use oxygen (O,) plasma to treat the back side of the PMMA/GR2M/Cu/GR2M multilayer structure. The etching time is 3min~5min. Etch away the GR2M at the bottom of Cu, and then proceed to A2 and subsequent steps: This method can appropriately reduce the number of (VH), S.0. solution etching and ultrapure water cleaning in step A.2. A.8 (VI) Examples of optical images taken after the transfer of copper-based graphene film growth are shown in Figures A and I. 7
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GB/T 40071—2021
Graphene
Optical images taken after the transfer of CVD-grown copper-based graphene film (substrate is 300nmSi0)2/Si) (Example) Figure A.1
rrKaeerkAca-1. Spin-coat a drop of polymethylmethacrylate (PMMA) at a speed of 3000/min onto the surface of a CVD-grown copper-based graphene film sample (i.e., GR2M/Cu/GR2M multilayer film) to form a PMMA/GR2M/Cu/GR2M multilayer film structure, in which PMMA is a transfer support layer and R2M refers to single-layer, double-layer, or few-layer graphene. A.2. Use 0.5 mol/L ammonium persulfate (NH4SO4) solution to slightly etch the Cu substrate of the sample and repeatedly clean it with ultrapure water. In this process, the PMMA/GR2M/Cu/GR2M multilayer film structure will float on the surface of the (NH4SO4) solution, the bottom Cu/GR2M layer will be dissolved, and the top PMMA/GR2M layer will remain in an unreacted state, thereby removing the GR2M at the bottom of Cu to obtain a PMMA/GR2M/Cu structure, and the body etching and cleaning steps are as follows: a) In (NH4SO4) solution. Float in the solution for 3 minutes, then float in ultrapure water for 5 minutes: b) Repeat step a) 3-5 times.
A.3 Use (NII)SO solution to completely etch away the Cu layer. Get a PMMA/CR2M multilayer film structure. The processing time of this step depends on the thickness of Cu and the concentration of (NII)SO. For example, the corrosion time of 25um thick Cu in 0.5mol/L (NII)SO solution is about 2 hours.
A.4: Float in ultrapure water for 30 minutes (this step can be performed multiple times). Each ultrapure water bath should be prepared in a separate container. A.5 Use 300nmSiO./Si substrate to pick up the PMMA/GR2M sample floating on the ultrapure water coating: Place H on a heating plate at 80℃ for 10 minutes to remove moisture, then place it on a heating plate at 180℃ for 15 minutes to relax the PMMA film. A.6 Soak PMMA/GR2M/300nmSiO./Si in ketone towel. Let it stand for 10 hours to dissolve the PMMA layer, then place GR2M/300nm SiO2/Si is sequentially placed in anhydrous ethanol and ultrapure water and soaked for 10 minutes each. After taking it out, it is blown with high-purity nitrogen for ten minutes to obtain a clean GR2M/300nmSi)/Si sample.
A.7 If the sample surface is not clean after the above steps, appropriately extend the time and number of corrosion or ultrapure water cleaning, or use 50°C acetone to dissolve the PMMA layer: the following steps are for reference: a) Increase or decrease the concentration of (VII).SO: solution to increase or decrease the corrosion rate. Low corrosion rate is beneficial to maintain the integrity of the sample during the corrosion process.
h) Select other etching solutions, such as FcCl, solution, etc. c): Select other organic materials as the transfer support layer, such as polydimethylsiloxane (PDMS for short): d) Use oxygen (O,) plasma to treat the back side of the PMMA/GR2M/Cu/GR2M multilayer structure. The etching time is 3min~5min. Etch away the GR2M at the bottom of Cu, and then proceed to A2 and subsequent steps: This method can appropriately reduce the number of (VH), S.0. solution etching and ultrapure water cleaning in step A.2. A.8 (VI) The optical images taken after the transfer of the grown copper-based graphene film are shown in Figures A and I. 7
-riKaeerkAca-
GB/T 40071—2021
Graphene
Optical images taken after the transfer of CVD-grown copper-based graphene film (substrate is 300nmSi0)2/Si) (Example) Figure A.1
rrKaeerkAca-1. Spin-coat a drop of polymethylmethacrylate (PMMA) at a speed of 3000/min onto the surface of a CVD-grown copper-based graphene film sample (i.e., GR2M/Cu/GR2M multilayer film) to form a PMMA/GR2M/Cu/GR2M multilayer film structure, in which PMMA is a transfer support layer and R2M refers to single-layer, double-layer, or few-layer graphene. A.2. Use 0.5 mol/L ammonium persulfate (NH4SO4) solution to slightly etch the Cu substrate of the sample and repeatedly clean it with ultrapure water. In this process, the PMMA/GR2M/Cu/GR2M multilayer film structure will float on the surface of the (NH4SO4) solution, the bottom Cu/GR2M layer will be dissolved, and the top PMMA/GR2M layer will remain in an unreacted state, thereby removing the GR2M at the bottom of Cu to obtain a PMMA/GR2M/Cu structure, and the body etching and cleaning steps are as follows: a) In (NH4SO4) solution. Float in the solution for 3 minutes, then float in ultrapure water for 5 minutes: b) Repeat step a) 3-5 times.
A.3 Use (NII)SO solution to completely etch away the Cu layer. Get a PMMA/CR2M multilayer film structure. The processing time of this step depends on the thickness of Cu and the concentration of (NII)SO. For example, the corrosion time of 25um thick Cu in 0.5mol/L (NII)SO solution is about 2 hours.
A.4: Float in ultrapure water for 30 minutes (this step can be performed multiple times). Each ultrapure water bath should be prepared in a separate container. A.5 Use 300nmSiO./Si substrate to pick up the PMMA/GR2M sample floating on the ultrapure water coating: Place H on a heating plate at 80℃ for 10 minutes to remove moisture, then place it on a heating plate at 180℃ for 15 minutes to relax the PMMA film. A.6 Soak PMMA/GR2M/300nmSiO./Si in ketone towel. Let it stand for 10 hours to dissolve the PMMA layer, then place GR2M/300nm SiO2/Si is sequentially placed in anhydrous ethanol and ultrapure water and soaked for 10 minutes each. After taking it out, it is blown with high-purity nitrogen for ten minutes to obtain a clean GR2M/300nmSi)/Si sample.
A.7 If the sample surface is not clean after the above steps, appropriately extend the time and number of corrosion or ultrapure water cleaning, or use 50°C acetone to dissolve the PMMA layer: the following steps are for reference: a) Increase or decrease the concentration of (VII).SO: solution to increase or decrease the corrosion rate. Low corrosion rate is beneficial to maintain the integrity of the sample during the corrosion process.
h) Select other etching solutions, such as FcCl, solution, etc. c): Select other organic materials as the transfer support layer, such as polydimethylsiloxane (PDMS for short), etc.: d) Use oxygen (O,) plasma to treat the back side of the PMMA/GR2M/Cu/GR2M multilayer structure. The etching time is 3min~5min. Etch away the GR2M at the bottom of Cu, and then proceed to A2 and subsequent steps: This method can appropriately reduce the number of (VH), S.0. solution etching and ultrapure water cleaning in step A.2. A.8 (VI) The optical pictures taken after the transfer of the grown copper-based graphene film are shown in Figures A and I. 7
-riKaeerkAca-
GB/T 40071—2021
Graphene
Optical pictures taken after the transfer of CVD-grown copper-based graphene film (substrate is 300nmSi0)2/Si) (Example) Figure A.1
rrKaeerkAca-
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