Optical Imaging and Characterization of Graphene and Other 2D Materials Using Quantitative Phase Microscopy

This article introduces
an optical microscopy technique for the
characterization of two-dimensional (2D) materials. The technique
is based on the use of quadriwave lateral shearing interferometry
(QLSI), a quantitative phase imaging technique that allows the imaging
of both the intensity and the phase of an incoming light beam. The
article shows how QLSI can be used to (i) image 2D materials with
high contrast on transparent substrates, (ii) detect the presence
of residues coming from the fabrication process, and (iii) map the
2D complex optical conductivity and complex refractive index by processing
the intensity and phase images of a light beam crossing the 2D material
of interest. To illustrate the versatility of this approach for 2D
material imaging and characterization, measurements have been performed
on graphene and MoS2.