2D Materials

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Characterization of MoS2 Flakes using TEOS
A flake of MoS2: the TEPL shift image derived from fitting the PL peak through regression analysis.
Both TEPL and TERS images are well correlated with AFM morphological images obtained simultaneously, and all are consistent in revealing the nature (number of layers) of MoS2 flakes. Upon deconvolution, the TEPL signal is even capable of revealing local inhomogeneities within a MoS2 flake of 100 nm size. Kelvin probe measurement supports TEPL and TERS measurements and adds to the power of such tip-enhanced combinative tools. TEOS characterization of 2D materials is likely to contribute to further deployment of these materials into commercial products through a better understanding of their electrical and chemical properties at the nanoscale.
Combined Raman and Photoluminescence Imaging of 2D WS2
Combined Raman and Photoluminescence Imaging of 2D WS2
Raman and photoluminescence spectroscopy reveal different aspects of the solid state structure of 2D materials. Raman and photoluminescence imaging performed simultaneously with one instrument reveals the spatial variation of the solid state structure and electronic properties of 2D crystals that is not revealed in reflected white light imaging. That ability should allow materials scientists to better design and fabricate electronic and optoelectronic devices based upon 2D crystals.
Characterization of Carbon Nanotubes Using Tip-Enhanced Raman Spectroscopy (TERS)
Characterization of Carbon Nanotubes Using Tip-Enhanced Raman Spectroscopy (TERS)
The use of TERS to reveal the defects density in the structure of CNTs is of interest for a better understanding of the electrical properties of the devices made with such nano-objects. Not only defects concentration but also local chirality changes from the different radial breathing modes, pressure effect and strain distribution can be studied at the single carbon nanotube level through TERS.
Number of Layers of MoS2 Determined Using Raman Spectroscopy
A combined (low-frequency and fingerprint) Raman map of MoS2 layers.
The two methods - Analysis of fingerprint modes (intralayer) and Analysis of low-frequency modes (interlayer) - give complementary results and allow the determination of the number of MoS2 layers. Method 2 (using low frequency modes) gives excellent contrast; however it does not show single layer regions (which is related to the nature of the modes, rising from interaction between at least two layers). Method 1 (using fingerprint modes) shows all the layers, but the contrast is poorer, particularly for higher numbers of layers. The best result can be obtained combining the two methods. All the measurements (low-frequency and fingerprint) were done using ultra-low frequency ULFTM filters which allow a high throughput measurement in a full Raman range, down to <10 cm-1.
Characterizing Lanthanides in Glasses for Optical Applications
Glasses are essential materials with a multitude of uses and many forms. In the area of optoelectronics there is an interest to modify the glass composition to favor the incorporation of lanthanide elements.