Thickness Mapping and Layer Number Identification of Exfoliated van der Waals Materials by Fourier Imaging Micro-Ellipsometry.

As performance of van der Waals heterostructure devices is governed by the nanoscale thicknesses and homogeneity of their constituent mono- to few-layer flakes, accurate mapping of these properties with high lateral resolution becomes imperative. Spectroscopic ellipsometry is a promising optical technique for such atomically thin-film characterization due to its simplicity, noninvasive nature and high accuracy. However, the effective use of standard ellipsometry methods on exfoliated micron-scale flakes is inhibited by their tens-of-microns lateral resolution or slow data acquisition.

Mapping spectroscopic micro-ellipsometry with sub-5 microns lateral resolution and simultaneous broadband acquisition at multiple angles.

Spectroscopic ellipsometry is a widely used optical technique in both industry and research for determining the optical properties and thickness of thin films. The effective use of spectroscopic ellipsometry on micro-structures is inhibited by technical limitations on the lateral resolution and data acquisition rate. Here, we introduce a spectroscopic micro-ellipsometer (SME), capable of recording spectrally resolved ellipsometric data simultaneously at multiple angles of incidence in a single measurement of a few seconds, with a lateral resolution down to 2 μm in the visible spectral range.