Nanomechanical spectroscopy of 2D materials

TL;DR

This paper presents a rapid, sensitive, and substrate-independent nanomechanical spectroscopy method for measuring the optical dielectric function of 2D materials across a broad spectral range, offering advantages over traditional techniques.

Contribution

Introduction of a novel nanomechanical platform that enables fast, substrate-independent spectroscopic measurements of 2D materials' dielectric functions without assumptions.

Findings

Measurement speed of approximately 135 ns.

High sensitivity with noise-equivalent power of 90 pW/√Hz.

Broad spectral range from 1.2 to 3.1 eV, extendable to UV-THz.

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 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 ($\tau_{rise}$ $\sim$ 135 ns), sensitive (noise-equivalent power = 90 $\frac{pW}{\sqrt{Hz}}$ ), and broadband (1.2 $-$ 3.1 eV, extendable to UV-THz) method provides an attractive alternative to spectroscopic or ellipsometric characterisation techniques.