Unveiling Buried Air Gaps and Interface Inhomogeneities in van der Waals Stacks via Microreflectance Mapping for Twistoptics Applications

Year: 2026

Type: article

Abstract: Van der Waals (vdW) heterostructures provide a versatile platform for multifunctional photonic and optoelectronic devices, yet their performance is often limited by interfacial inhomogeneities that perturb the local dielectric environment. This is particularly critical in polaritonic heterostructures, where the near-field optical response is extremely sensitive to buried defects. Here, we present a high-resolution microreflectance mapping technique for assessing interfacial quality in vdW heterostructures and enabling the fabrication of twisted polaritonic stacks. By combining hyperspectral imaging with transfer-matrix-method (TMM) fitting, we determine flake thickness directly on PDMS stamps and quantify buried air gaps and other interfacial nonuniformities in assembled stacks. Using h-BN and α-MoO3 heterostructures as benchmark systems, we detect buried air gaps down to 7 nm with ∼1 μm lateral resolution. Correlation with scattering-type scanning near-field optical microscopy (s-SNOM) confirms the quantitative accuracy of the method and shows that nanometric air gaps already produce measurable changes in phonon-polariton (PhP) propagation. Our results establish microreflectance mapping as an accessible far-field approach for quantitative interfacial control in polaritonic heterostructures, a key requirement for twistoptics applications. To facilitate implementation, we provide the analysis in an open-source graphical user interface that can be integrated into standard optical-microscope setups.

Source: ACS Applied Nano Materials

DOI: 10.1021/acsanm.6c02110

Authors: Julia G. Prieto, Adam Roselló, Abel Martínez-Suárez, Enrique Terán-García, Christian Lanza, Yolanda Álvarez, Stephan Kasemann, Stefan Partel, Kenji Watanabe, Takashi Taniguchi, Adrián Fernández-Gavela, Dimas G. de Oteyza, Luis Javier Martínez, Aitana Tarazaga Martín-Luengo, Pablo Alonso-González, Javier Martín-Sánchez

Institutions: Consejo Superior de Investigaciones Científicas, Universidad de Oviedo, Donostia International Physics Center, Vorarlberg University of Applied Sciences, National Institute for Materials Science

Language: English

Topic: 2D Materials and Applications

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $4,500

Funders: Gobierno del Principado de Asturias, Ministry of Education, Culture, Sports, Science and Technology, Ministerio de Ciencia e Innovación, Universidad de Oviedo, QuantERA, European Research Council, Japan Society for the Promotion of Science, National Institute for Materials Science, Agencia Estatal de Investigación, Core Research for Evolutional Science and Technology, HORIZON EUROPE European Research Council

OpenAlex ID: W7203693393