2D Materials

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2D material is defined as a crystalline material consisting of a single unit cell layer of that material. In particular, graphene and transition metal dichalcogenides (TMDCs) are attracting attention as next-generation semiconductor materials. When used as a semiconductor, precise structural analysis is important because its crystal structure and crystallinity greatly affect performance.

Structural Analysis | Film Thickness and Quality | Crystal Defect Analysis | Foreign Object Detection/Analysis

Structural Analysis

Structural characterization of WS₂ flakes by Photoluminescence and ultra-low frequency Raman spectroscopy on a unique multimode platform

2D materials are state-of-the-art in nano- and opto-electronics. Characterizing their structural properties with a non-destructive approach at the micron scale is very important.

TERS Characterization of Graphene Nanoribbons

This application note reports on the TERS nanocharacterization of graphene nanoribbons (GNRs) fabricated by electron beam lithography. The chemical nanoresolution achievable by TERS reveals the presence of amorphous carbon at the edge of the GNRs and locates organic residues. TERS can be considered as a valuable tool for characterizing nanopatterned graphene, an essential step for the development of graphene-based nano-devices.

Correlated TERS, TEPL and SPM Measurements of 2D Materials

Many challenges remain before the promise of 2D materials is realized in the form of practical nano-devices. An information-rich, nanoscale characterization technique is required to qualify these materials and assist in the deployment of 2D material-based applications.

Correlated TERS and KPFM of Graphene Oxide Flakes

AFM-Raman and its TERS mode are used to show nanoscale surface mapping of structural defects and chemical groups on graphene oxide (GO) flakes with 10 nm spatial resolution. The multi-parameter measurement methodology proposed in this note extends the capability of TERS allowing a direct correlation of local chemical composition and physical properties at the nanoscale not only for 2D materials but for almost any sample surface.

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.

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.

A combined (low-frequency and fingerprint) Raman map of MoS2 layers.

There are two types of vibrational modes in MoS2 (as in all layered structures): vibrational modes inside layers (intralayer) and modes resulting from the movements of complete layers (interlayer).

Combined Raman and Photoluminescence Imaging of 2D WS2

Raman and photoluminescence spectroscopy and imaging are used to examine the spatial variation of solid state structure and electronic character of two dimensional (2D) WS2 crystals. Simultaneous acquisition of photoluminescence spectra with the Raman scattering provides complementary ways of rendering Raman and photoluminescence spectral images of thin film WS2.

Film Thickness and Quality

In the advancement of thin film technology through miniaturization, we propose solutions for achieving high film deposition control, such as in-situ evaluation during the film deposition process and evaluation of thin films at the Ångström order level.

Thin film analysis in liquid: Analysis using a spectroscopic ellipsometer liquid measurement cell
In situ thin film evaluation: In-chamber wafer analysis by incorporating analytical parts into the chamber

Membrane information obtained using a spectroscopic ellipsometer

Crystal Defect Analysis

Reducing defects and precisely controlling impurities have become increasingly important in semiconductor devices for high-speed communication. We will introduce analysis cases illustrating this.

Micro area crystal defect evaluation: High spatial resolution defect evaluation using TEPL

Foreign Object Detection/Analysis

Defects in wafers can also be caused by foreign matter, and we will introduce a method of microscopic elemental analysis to identify the cause of defects.

Reticle/mask foreign object detection: High-throughput foreign object detection
Foreign matter removal device on wafers: Automatic foreign matter removal device using blow & vacuum suction