Nanomechanical Spectroscopy of 2D Materials

Nano Lett. 2022 Oct 26;22(20):8037-8044. doi: 10.1021/acs.nanolett.2c01289. Epub 2022 Oct 17.

Abstract

We introduce a nanomechanical platform for fast and sensitive measurements of the spectrally resolved optical dielectric function of 2D materials. At the heart of our approach is a suspended 2D material integrated into a high Q silicon nitride nanomechanical resonator illuminated by a wavelength-tunable laser source. From the heating-related frequency shift of the resonator as well as its optical reflection measured as a function of photon energy, we obtain the real and imaginary parts of the dielectric function. Our measurements are unaffected by substrate-related screening and do not require any assumptions on the underling optical constants. This fast (τrise ∼ 135 ns), sensitive (noise-equivalent power = 90pWHz), and broadband (1.2-3.1 eV, extendable to UV-THz) method provides an attractive alternative to spectroscopic or ellipsometric characterization techniques.

Keywords: 2D materials; NEMS; Nanomechanical resonators; silicon nitride; spectroscopy; transition metal dichalcogenides (TMDs).