Spectroscopic Ellipsometry Advances Non-Destructive Analysis of Two-Dimensional Materials and Van Der Waals Structures

Spectroscopic ellipsometry now plays a crucial role in understanding the unique optical properties of two-dimensional materials, which hold immense promise for future technologies.

Ersyzario Edo Yunata, Angga Dito Fauzi, and Khoirunnisa Qoulan Aziza, all from Airlangga University, alongside their colleagues, present a comprehensive overview of how this non-destructive technique reveals the complex behaviour of materials just a few atoms thick. Their work details the methods used to probe these materials, including advanced approaches like Mueller matrix ellipsometry, and addresses the challenges of accurately modelling their optical response, considering factors like anisotropy and substrate interactions. By showcasing recent discoveries, such as extreme optical anisotropy and tunable plasmonic responses, this research establishes spectroscopic ellipsometry as an essential tool for both fundamental scientific investigation and the development of innovative photonic devices based on two-dimensional materials. Researchers investigate how SE measures changes in light polarization upon reflection, allowing precise determination of film thickness, refractive index, and extinction coefficient. This work details how SE assesses a wide range of materials, including semiconductors, dielectrics, and metals, offering insights into their composition and structure at the nanoscale. The review highlights SE as a non-destructive, sensitive, and versatile technique for materials science and engineering, demonstrating its utility in diverse fields such as microelectronics, optics, and surface science. Ellipsometry Reveals 2D Material Optical Properties Spectroscopic Ellipsometry (SE) has become a crucial technique for thoroughly investigating the optical properties of two-dimensional (2D) materials, including graphene and transition metal dichalcogenides. Researchers employ SE to precisely determine the complex dielectric function, a fundamental property describing a material’s interaction with light, and to reveal details of its electronic and excitonic structure. This work demonstrates how SE overcomes challenges inherent in characterizing atomically thin materials, such as weak optical signals and sensitivity to external factors. The study utilizes SE to analyze how synthesis techniques, substrate materials, and temperature influence the optical spectra of 2D materials. The technique excels at resolving subtle optical features, even in materials where conventional methods struggle due to limited sensitivity. Researchers carefully measure the change in polarization state of light reflected from a sample using SE. This data is then modeled using sophisticated optical algorithms to extract information about the material’s thickness, refractive index, and extinction coefficient as a function of wavelength.

The team developed methods to accurately determine the impact of environmental factors and material imperfections on the measured spectra. By carefully analyzing the polarization change, scientists can map the excitonic landscape of 2D materials, including neutral excitons, trions, and higher-order excitonic complexes. This approach enables detailed characterization of phenomena such as environment- and synthesis-dependent excitonic shifts, redshifted transitions in graphene on nickel, high refractive indices in multilayer materials, and naturally occurring hyperbolic dispersion in metallic materials. The study highlights the exceptional capability of SE to resolve dielectric functions, excitonic resonances, optical anisotropy, interlayer interactions, and substrate-induced effects, establishing it as a cornerstone for both fundamental studies and the development of advanced photonic devices.

Accurate Dielectric Function of 2D Materials This extensive research paper details the application of Spectroscopic Ellipsometry (SE) as a crucial characterization technique for two-dimensional (2D) materials. The paper highlights SE’s ability to accurately determine the optical constants, crucial for modeling and predicting the behavior of 2D materials. SE is used to study a wide range of 2D materials, including transition metal dichalcogenides, graphene, and their layered heterostructures. SE helps in understanding exciton binding energies and Rydberg series in monolayer materials, providing insights into their electronic structure. The technique reveals anisotropic optical properties and hyperbolic behavior in certain 2D materials, opening possibilities for novel optical devices. SE is effective in characterizing the optical properties of complex heterostructures formed by stacking different 2D materials. The paper discusses the importance of using appropriate models to distinguish between the optical response of thin films and truly isolated single-layer 2D materials. The use of imaging SE allows for spatially resolved characterization of 2D materials, revealing variations in optical properties across the sample. Researchers envision the use of real-time SE to monitor the growth and processing of 2D materials, linking optical properties directly to fabrication parameters. The integration of machine learning algorithms with SE data analysis promises to automate model selection, improve accuracy, and accelerate the characterization process. The obtained optical constants serve as crucial inputs for simulations to design and optimize devices based on 2D materials.

This research underscores the importance of Spectroscopic Ellipsometry as a powerful and versatile tool for characterizing 2D materials. The detailed analysis of optical properties is essential for advancing our understanding of these materials and for realizing their full potential in next-generation optoelectronic devices. Ellipsometry Reveals 2D Material Optical Properties Spectroscopic ellipsometry has proven to be a powerful technique for characterizing the optical properties of two-dimensional materials, offering quantitative access to the complex dielectric function and revealing crucial information about light-matter interactions at the nanoscale. Measurements consistently demonstrate the ability to precisely determine optical constants and film thickness, even for single-layer materials, and have directly quantified strong excitonic resonances and spectral splitting in transition-metal dichalcogenides under specific growth conditions. The technique’s sensitivity also extends to understanding how external factors, such as the substrate or fabrication method, influence optical responses, revealing effects like charge transfer, interfacial hybridization, and the control of many-body physics through synthesis parameters. Furthermore, advanced ellipsometric methods, notably Mueller Matrix Ellipsometry, have enabled the investigation of complex anisotropic and hyperbolic phenomena in layered materials. Findings consolidate evidence of extreme optical properties, including record-high refractive indices and strong birefringence in multilayer transition-metal dichalcogenides, positioning them as promising candidates for nanophotonic applications. The identification of naturally occurring hyperbolic dispersion in metallic materials further expands the potential of these systems for manipulating light. While the technique provides detailed optical characterization, it benefits from complementary analysis with techniques like Raman spectroscopy and atomic force microscopy to refine optical models and ensure accurate interpretation of results. 👉 More information 🗞 Spectroscopic Ellipsometry for Two-Dimensional Materials: Methods, Optical Modeling, and Emerging Phenomena 🧠 ArXiv: https://arxiv.org/abs/2512.14294 Tags: