The role of Raman spectrometer in graphene related experiments.

Raman Spectrometer Play The Important Role In Graphene Related Experiments.

2021-01-06

Raman spectrometer is an instrument used to detect Raman scattering signals of materials. The detection process of Raman spectrometer includes three steps of excitation, collection, and analysis. First, the Raman spectrometer emits excitation light to excite the sample to generate a Raman scattering signal. Then the Raman spectrometer collects the scattered Raman signal and transmits it to the spectrum detection unit. Finally, the spectral detection unit performs spectral analysis on the Raman signal. Because the Raman scattering cross-section is small, the signal is very weak, and the strong Rayleigh scattering needs to be suppressed when measuring Raman signals, so the Raman spectrometer needs to have a strong-weak signal detection ability and excitation light suppression ability. Raman spectrometers can be divided into two types: large Raman spectrometers and portable Raman spectrometers.

The portable Raman spectrometer can be regarded as the smallest functional unit of a large Raman spectrometer. The basic structure of the portable Raman spectrometer mainly includes three parts: excitation light source, optical probe, and spectrum detection unit. A typical portable Raman spectrometer is different from a large Raman spectrometer. The portable Raman spectrometer is small in size and convenient to carry, which can meet the needs of on-site measurement and online detection. The research and development of domestic portable Raman spectrometers started late, and one of the main manufacturers is our company Optosky Photonics Inc. . So many lab will use our Raman spectrometers to do some research and experiment.

For example, Xiamen University’s Dr. Zhang Chentao did research on the rapid preparation method of graphene-based on L-CVD and the design of the preparation device.

He used a Raman spectrometer to characterize the graphene transferred to Si02/Si. Figure 2(a) shows the Raman spectra of areas A, B, and C in Figure 1. It can be seen from the figure that there is no obvious D peak in the Raman spectra of regions A, B, and C, indicating that the prepared graphene has no obvious defects. In area A, the ratio of 2D peak to G peak is about 1, and the graphene in this area is a double layer. In regions B and C, the ratio of graphene 2D peak to G peak is less than 1, indicating that the graphene in these two regions is multi-layer (3-4 layers). In order to obtain the overall layer number information of graphene, a Raman Mapping test was performed on graphene strips. Figure 2(b) shows the ratio of peak 2D to peak G in the dotted area in Figure 1. It can be seen from the figure that the ratio of the 2D peak to the G peak in most areas is 0.62-0.81, indicating that the graphene in most areas has 3 to 4 layers.

Figure 2(a) shows the Raman spectrum of the laser scanning path of the nickel substrate when the laser moves at a speed of 20gm/s relative to the nickel substrate. The D peak in the figure is obvious, and the 2D peak is asymmetric on the left and right sides, which is a superposition of multiple sub-peaks, indicating that the material grown at a scanning speed of 20 p/s is graphite. In addition, traces of the dissolution of the nickel substrate can be clearly observed on the laser scanning path of the nickel substrate, indicating that the heating temperature has reached the dissolution temperature of the nickel material.
The Raman spectrum corresponding to the relative movement speed of the laser and the nickel substrate at 80 μm/s is shown in Figure 2(c). At this time, the shape of the 2D peak is symmetrical and there is no obvious D peak in the Raman spectrum, indicating that the material grown on the laser scanning path is multilayer graphene, and the graphene structure is almost defect-free.
When the relative movement speed of the laser and the nickel substrate is 110 μm/s, since the substrate cannot be heated to the graphene growth temperature, the methane molecules cannot be decomposed, and the Raman peak of the carbon material is not detected on the laser scanning path.

Do you want to know about which Raman spectrometer they use?——Optosky’s ATR8300

ATR8300 is equipped with a tailor-made objective, and a Raman laser spot on the sample becomes very close to the diffraction limit, then focal information can be displayed accurately and intuitively on the screen with the 3-megapixel camera. This configuration improves Raman spectral quality for overcoming the limitations of Raman systems where the focal plane for Raman signal collection is slightly above or below the imaging plane.

ATR8300 works stably with no moving components of optical path switch, hence it avoids loss of the optical path while imaging formed, and it gains an optimized signal for separating imaging formed from Raman signal collection.

Features: