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GB/T 40069-2021: Nanotechnologies - Measurement of the number of layers of graphene-related two-dimensional (2D) materials - Raman spectroscopy method
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Nanotechnologies - Measurement of the number of layers of graphene-related two-dimensional (2D) materials - Raman spectroscopy method
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GB/T 40069-2021
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Basic data | Standard ID | GB/T 40069-2021 (GB/T40069-2021) | | Description (Translated English) | Nanotechnologies - Measurement of the number of layers of graphene-related two-dimensional (2D) materials - Raman spectroscopy method | | Sector / Industry | National Standard (Recommended) | | Classification of Chinese Standard | N35 | | Word Count Estimation | 30,389 | | Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration | GB/T 40069-2021: Nanotechnologies - Measurement of the number of layers of graphene-related two-dimensional (2D) materials - Raman spectroscopy method
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(Nanotechnology Layer number measurement of graphene-related two-dimensional materials Raman spectroscopy)
ICS 17.180.30
CCSN35
National Standards of People's Republic of China
Nanotechnology graphene-related two-dimensional materials
Layer number measurement Raman spectroscopy
Released on 2021-05-21
2021-12-01 implementation
State Administration of Market Supervision and Administration
Issued by the National Standardization Management Committee
Table of contents
Foreword Ⅲ
Introduction Ⅳ
1 Scope 1
2 Normative references 1
3 Terms and definitions 1
4 Sample preparation 3
5 Raman spectroscopy (A method) for linear measurement of graphene flake layers based on 2D model 3
6 Raman spectroscopy (B method) for measuring the number of graphene flakes based on the peak height of the silicon Raman mode on the SiO2/Si substrate 5
7 Test report 7
Appendix A (informative) Summary list of various methods for measuring the number of graphene flakes by Raman spectroscopy 8
Appendix B (informative) Raman spectroscopy (C method) for measuring the number of graphene flake layers based on G mode peak height 9
Appendix C (Informative) Schematic diagram of the spectral parameters of a typical Raman peak 12
Appendix D (informative) Transfer operation steps of graphene-related two-dimensional materials 13
Appendix E (Informative) Raman Spectroscopy (Method A) Characterization Example of Linear Measurement of Graphene Sheet Layers Based on 2D Model 15
Appendix F (Informative) Raman spectroscopy for measuring the number of graphene flakes based on the peak height of the silicon Raman mode on SiO2/Si substrate (Method B)
Characterization example 17
Appendix G (Informative) Raman spectroscopy for measuring the number of graphene flakes based on the peak height of the silicon Raman mode on the SiO2/Si substrate (Method B)
IG(Si)/I0(Si) theoretical calculation results (532nm laser) 19
Appendix H (Informative) Raman spectroscopy for measuring the number of graphene flakes based on the peak height of the silicon Raman mode on the SiO2/Si substrate (Method B)
(633nm laser) 20
Appendix I (Informative) Sample Test Report 22
Appendix J (Informative) Characterization example of Raman spectroscopy (C method) for measuring the number of graphene flake layers based on G-mode peak height 23
References 25
Nanotechnology graphene-related two-dimensional materials
Layer number measurement Raman spectroscopy
Warning. This document involves the use of lasers, which may cause irreversible damage to the eyes. Should be worn when using a laser
For the corresponding laser protective glasses, it is strictly forbidden to look directly at the laser with your eyes to avoid the laser from entering the human eyes through the reflection of the optical elements. The operator should accept the phase
Close safety training.
1 Scope
This document specifies a method for measuring the number of layers of graphene-related two-dimensional materials using Raman spectroscopy.
This document is suitable for the measurement of the number of layers of graphene flakes with a lateral dimension of not less than 2 μm prepared by the mechanical peeling method. Chemical gas
The graphene flakes stacked with AB or ABC prepared by the phase deposition (CVD. chemical vapordeposition) method can refer to this method
Law enforcement.
Note 1.When measuring the number of layers of graphene flakes, several methods can be combined alone or combined to measure and verify each other.
Note 2.Chapter 5 gives the line type based on 2D mode (A method). Chapter 6 shows the peak height of the silicon Raman mode (B method) based on the SiO2/Si substrate for graphene
Raman spectroscopy for the measurement of the number of slices. Appendix A gives a summary list of various methods for measuring the number of graphene flakes by Raman spectroscopy. Appendix B
The Raman spectroscopy method for measuring the number of graphene flake layers based on the peak height of the graphene flake G mode (C method) is given.
2 Normative references
The contents of the following documents constitute the indispensable clauses of this document through normative references in the text. Among them, dated quotations
Only the version corresponding to the date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to
This document.
GB/T 30544.13 Nanotechnology terminology Part 13.Graphene and related two-dimensional materials
GB/T 33252 Nanotechnology Laser Confocal Raman Microscope Performance Test
JJF1544 Raman Spectrometer Calibration Specification
3 Terms and definitions
The following terms and definitions defined in GB/T 30544.13 and GB/T 33252 apply to this document.
3.1 Terms related to graphene-related two-dimensional materials
3.1.1
Graphene-related 2D material; GR2M
Carbon-based two-dimensional material with no more than 10 layers.
Note. Including graphene, double-layer graphene, few-layer graphene, graphene oxide, etc.
3.1.2
Grapheneflake grapheneflake
Graphene nanosheet graphenenanoplate; graphenenanoplatelet; GNP
Nanosheets composed of graphene layers.
Note. The common thickness is less than 3nm, and the lateral size range is about 100nm~100μm.
[Source. GB/T 30544.13-2018, 3.1.2.11, with modification]
3.1.3
Numberoflayers
< Two-dimensional material> The number of layers constituting the two-dimensional material.
3.2 Terms related to Raman spectroscopy
3.2.1
Raman spectrum Ramanspectrum
When a substance is irradiated with monochromatic radiant energy, the frequency-shifted spectrum is modulated due to inelastic scattering.
Note 1.Inelastic scattering refers to the rotation excitation, vibration excitation or phonon excitation of the medium.
Note 2.Modulation frequency shift refers to the energy loss or gain of monochromatic radiation photons.
[Source. GB/T 33252-2016, 2.1]
3.2.2
Ramanpeak;Ramanmode;Ramanband
The Raman spectrum has a certain shape of peaks.
Note 1.Each scattering medium has its specific Raman peak.
Note 2.Including peak position, peak height, peak area, peak width and line type and other spectral characteristics, see Appendix C Figure C.1.
3.2.3
Peak height peakheight; peakmaximum
The vertical distance between the highest point of the Raman peak and the baseline.
3.2.4
Peakarea
Peak intensity
The area enclosed by the Raman peak and the baseline.
3.2.5
Peakposition
The wavenumber difference between the incident monochromatic light and the position of the highest point of the Raman peak.
Note. Also called Raman frequency shift, the unit is wave number (cm-1).
3.2.6
Peakwidth
The frequency shift difference between the two sides of the Raman peak at 1/2 peak height.
Note. Also known as Ful Width at Half Maximum (FWHM).
3.2.7
Gmode
G peak
A characteristic peak related to the stretching vibration between the nearest neighboring carbon atoms in the graphene layer.
Note 1.Generally located near 1582cm-1, has nothing to do with the number of graphene layers.
Note 2.G peak frequency shift will be affected by factors such as stress and carrier concentration.
3.2.8
Dmode Dmode
Peak D
The characteristic peaks located at 1300cm-1~1400cm-1 related to the structural defects in the edges of the graphene sheet and the layers.
Note 1.The D mode is a TO phonon mode near the K point of the Brillouin zone boundary by a disorderly activated graphene-related two-dimensional material. Peak height ratio of D mode to G mode
The size can reflect the disorder degree of the graphene lattice structure to a certain extent.
Note 2.The D-mode frequency shift is related to the photon energy of the excitation light, and is generally linear, with a slope of 50cm-1/eV.
3.2.9
2D mode 2Dmode
2D peak
The characteristic peaks of graphene flakes are located at 2600cm-1~2800cm-1.
Note 1.Also known as G'mode, its frequency is close to twice the frequency of D mode. The line type is related to the electronic band structure of graphene-related two-dimensional materials.
Note 2.The 2D mode frequency shift is related to the photon energy of the excitation light, and is generally linear, with a slope of about 100cm-1/eV.
4 Sample preparation
4.1 The substrate used in this document should be a silicon (Si) substrate with a silicon dioxide (SiO2) layer of 90nm±5nm thick on the surface, which is referred to as
90nmSiO2/Si substrate.
4.2 For the graphene sheet prepared by the mechanical peeling method on the 90nmSiO2/Si substrate, it can be used directly without further processing.
4.3 For graphene flake samples prepared by CVD, the samples need to be transferred to a 90nmSiO2/Si substrate (see appendix for specific steps)
D).
4.4 Observe the sample under the microscope, and there should be no obvious impurities in the test area.
5 Raman spectroscopy (A method) for linear measurement of the number of graphene flakes based on a 2D model
5.1 Principle
The principle of Raman spectroscopy (A method) for linear measurement of graphene flakes based on 2D mode is as follows.
a) The 2D peak of the graphene sheet is derived from the double resonance Raman scattering process of TO phonons near the K point of the Brillouin zone boundary, so it is not
The 2D model of the same number of graphene sheets shows a unique line shape. Single-layer graphene has linear properties near the Dirac point
The 2D mold activated by the double resonance Raman scattering based on the band structure has a single Lorentz line and is not affected by a single layer of graphite.
The influence of the preparation method of the alkene and the substrate placed on it. With the change in the number of graphene flake layers, the line of the graphene flake 2D mold
The type also changes significantly, and the line type is closely related to the wavelength of the excitation light.
b) For specific laser lines, such as 633nm laser, single-layer and 2~4 layer AB stacked graphene sheets have unique
2D mold line type, as shown in Figure 1.But these features are not obvious under 532nm laser excitation, so the number of layers of graphene flakes
It can be judged by the line type of the 2D mode excited by the 633nm laser.
c) This method is suitable for single-layer graphene and graphene sheets with AB stacking and no more than 4 layers.
Note 1.The 2D mold line type of single-layer graphene (1LG) is a single Lorentz line type. The 2D peak of the 2~4 layer graphene sheet consists of multiple sub-peaks, and its linear
Detailed features are marked with arrows, plus signs and asterisks.
Note 2.The 2D peak linear feature of the 2-layer graphene sheet (2LG) is that there is an obvious sub-peak on the left side (indicated by the arrow) in addition to the main peak.
Note 3.The 2D peak linear characteristics of the 3-layer graphene sheet (3LG) are. a) There are two sub-peaks on the left side of the main peak (shown by the arrow); b) The main peak in the middle has two sub-peaks (plus
The peak height of the sub-peak on the left (small frequency shift) is significantly higher than that of the sub-peak on the right (large frequency shift); c) There is a sub-peak on the right side of the main peak (shown by an asterisk).
Note 4.The 2D peak linear characteristics of the 4-layer graphene sheet (4LG) are. a) There are three sub-peaks (shown by arrows) on the left side of the main peak, which are located at 2592cm-1 and 2
The two sub-peaks near 623 cm-1 are more obvious; b) The main peak in the middle has two sub-peaks (shown by the plus sign), and their peak heights are close; c) There is a sub-peak on the right side of the main peak
Peaks (shown by asterisks).
Note 5.With the increase of the number of layers, the number of sub-peaks on the left and right sides of the main peak of the 2D peak of the graphene sheet with 5 layers and above gradually increases, due to the overlap between the peaks.
As a result, the spectral characteristics between multilayer graphene sheets with different layer thicknesses are no longer easy to distinguish. The 2D mold line type of graphite (HOPG) is characterized by a sharp
A sharp main peak and a wider sub-peak on the left.
Figure 1 Raman spectrum of 2D mode excited by 633nm laser
5.2 Apparatus
5.2.1 Use laser confocal Raman microscope as measuring instrument; use 633nm laser; laser confocal Raman microscope
The wave number covered by a single array detector element should be better than 1.0cm-1, and the silicon material measured by the spectrometer is located at the 520cm-1 Raman mode.
FWHM is not greater than 4.0cm-1; the lateral (XY) spatial resolution of the laser confocal Raman microscope should not be greater than 2μm.
5.2.2 Before measurement, the Raman spectrometer should be calibrated according to GB/T 33252, JJF1544 or related technical specifications.
5.3 Measurement procedure and determination of the number of layers
5.3.1 Use a microscope objective lens with a magnification of 100 times or 50 times; the laser power reaching the sample surface should be less than 0.5 mW.
Avoid the sample being heated and damaged by the laser.
5.3.2 The selected spectral scan range should be greater than 2450cm-1~2800cm-1.
5.3.3 Use an optical microscope to analyze the image of the sample on the substrate, clarify the position of the graphene sheet, and determine the measurement area.
5.3.4 Choose an appropriate Raman spectrum acquisition time for the sample to be tested, and the 2D peak height should be counted above 5000.
5.3.5 In the area with the same chromaticity in the sample to be tested, select different locations to measure 3 sets of data and take the arithmetic average.
5.3.6 Obtain the Raman spectrum of the 2D peak of the sample to be tested, and compare it with Figure 1 to obtain the corresponding number of layers. If the measured spectrum is similar to that in Figure 1
If the main characteristics of the 2D mold line type of the 1LG~4LG samples do not match, the graphene sheet does not have an AB stacking method or the number of layers exceeds
4th floor. Refer to Appendix E for characterization examples.
6 Raman spectroscopy (B method) for measuring the number of graphene flakes based on the peak height of the silicon Raman mode on the SiO2/Si substrate
6.1 Principle
The principle of Raman spectroscopy (B method) for measuring the number of graphene sheets based on the peak height of the silicon Raman mode of the SiO2/Si substrate is as follows.
a) The Raman spectra of graphene sheets with different layers also show different characteristics in terms of the peak height of the characteristic Raman mode. Graphene flakes
When placed or transferred to a SiO2/Si substrate, the laser and Raman modes are more likely to occur in the graphene sheet and its upper and lower media.
The reflected and refracted beams will interfere with each other, making the Raman peak height of the silicon of the SiO2/Si substrate under the graphene sheet and the excitation light
The wavelength, the type of substrate used and the characteristic thickness, the numerical aperture of the objective lens, and the number of graphene sheets are related. Laser excitation of a certain wavelength
When the graphene sheet covered SiO2/Si substrate is located at 520.7 cm-1, the peak height of the silicon Raman characteristic peak is IG (Si), and
The peak height of the silicon Raman characteristic peak of the substrate without graphene sheet coverage is I0 (Si), as shown in Figure 2.IG(Si) can be used
I0(Si) to normalize. Use the transfer matrix method to calculate the numerical aperture of the substrate and the microscope objective with a specific SiO2 layer thickness
Under a certain wavelength of laser excitation, the relationship between the ratio of IG(Si)/I0(Si) and the number of graphene sheets.
Figure 2 Schematic diagram of IG (Si) and I0 (Si) on SiO2/Si substrate
b) Before the test, it is necessary to accurately measure the thickness of the SiO2 layer covering the surface of the SiO2/Si substrate.
The numerical aperture of the mirror is calculated, and the relationship between IG(Si)/I0(Si) and the number of graphene sheets is calculated. Figure 3 shows the magnification of the microscope objective
Is 50, the numerical aperture is 0.50, and the SiO2 thickness is 90nm, the relationship between IG(Si)/I0(Si) and the number of layers under 532nm excitation
On the calculation results, the specific values are shown in Table 1.It can be seen that the ratio IG(Si)/I0(Si) and the number of graphene flake layers are monotonously changing.
This can measure the number of layers of graphene flake samples within 10 layers of AB stacking and ABC stacking on a specific substrate.
Figure 3 When the excitation light wavelength is 532nm, the SiO2 thickness hSiO2 on the surface of the SiO2/Si substrate is 90nm, and the numerical aperture NA is equal to 0.50
Theoretical calculation results of the relationship between IG(Si)/I0(Si) and the number of graphene sheets (diamond points)
6.2 Apparatus
6.2.1 Use laser confocal Raman microscope as measuring instrument; use 532nm laser; single array detector element of spectrometer
The covered wavenumber should be better than 1.0cm-1, and the FWHM of the silicon material in the 520cm-1 Raman mode measured by the spectrometer should not be greater than
4.0cm-1; the lateral (XY) spatial resolution of the Raman spectrometer should not be greater than 2μm.
6.2.2 Before measurement, the Raman spectrometer should be calibrated. The calibration requirements are the same as 5.2.2.
6.3 Measurement procedure and determination of the number of layers
6.3.1 Use a microscope objective lens with a magnification of 50 times and a numerical aperture of not greater than 0.55; the laser power reaching the sample surface should be less than
0.5mW, to avoid the sample being heated and damaged by the laser.
6.3.2 The selected spectral scan range should be greater than 450cm-1~600cm-1.
6.3.3 Use an optical microscope to analyze the image of the sample on the substrate, grasp the position of the graphene sheet, and determine the measurement area. Get to be tested
Raman mode peak height of SiO2/Si substrate without graphene flake coverage near graphene flakes I0(Si). Raman mode peak height and test time excitation
The light is very sensitive to the focus state of the sample, and it is necessary to accurately focus the SiO2/Si substrate first, so that the center of the laser spot is aligned with the bare area near the sample to be tested.
On the exposed substrate that is not covered by obvious impurities, finely adjust the relative distance between the objective lens and the substrate (that is, fine-tune the focus) to obtain Si Raman mode
The focus state when the peak height is maximum. Choose the appropriate Raman spectrum acquisition time, and the Si peak height should be counted above 5000.Use the Lorentz line
The value of peak height I0 (Si) is obtained by type fitting.
6.3.4 Obtain the Raman mode peak height IG(Si) of the SiO2/Si substrate on the graphene sheet sample area to be tested. keep the focus when measuring I0(Si)
The state remains unchanged, and the sample position is translated, so that the center of the laser spot is aligned with the graphene sheet sample area to be tested, and the acquisition time is the same as that in 6.3.3.
The Raman mode peak height IG(Si) of the SiO2/Si substrate covered by the graphene flake sample. Use Lorentz linear fitting to get the peak height IG(Si)
Numerical value.
6.3.5 Calculate the relative ratio of peak height IG(Si)/I0(Si).
6.3.6 Compare IG(Si)/I0(Si) with the theoretical calculation results in Table 1, and the corresponding number of layers will be rounded to the nearest integer. According to the party
The method can determine the number of graphene sheets with 1 to 10 layers. Refer to Appendix F for measurement examples.
Table 1 Theoretical calculation results of the relationship between IG(Si)/I0(Si) and the number of graphene sheets (532nm)
(532nm laser, substrate SiO2 thickness is 90nm, numerical aperture is 0.50)
6.3.7 In the area with the same chromaticity in the sample to be tested, select different locations to measure 3 sets of data and take the arithmetic average.
6.3.8 For the case where the thickness of the substrate SiO2 is not 90nm±5nm, it is necessary to accurately measure the thickness of the SiO2 layer on the SiO2/Si substrate, and
According to the thickness, laser wavelength and the numerical aperture of the objective lens, the relationship between IG(Si)/I0(Si) and the number of graphene sheets is calculated. in difference
Under the conditions of numerical aperture and SiO2 layer thickness, the theoretical calculation ratio of IG(Si)/I0(Si) and the number of graphene sheets when excited by a 532nm laser
See Table G.1 in Appendix G for the relationship.
6.3.9 The above method can be extended to the case of 633nm laser wavelength. About the use of 633nm laser to measure the number of graphene sheets
For details, see Appendix H.
7 Test report
The test report should include but not limited to the following.
---According to the standard;
---Measurement methods;
---Test date;
---Measurer;
---Sample information;
---The type, brand, model of the test instrument, the model of the detector, etc.;
---Experimental conditions, including excitation wavelength, laser power reaching the sample surface, number of grating lines, etc.;
---Raman spectrum and layer number results;
---When necessary, uncertainty analysis.
Refer to Appendix I for the reference format of the test report.
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