Nanomechanical Spectroscopy of 2D Materials.

Kirchhof, Jan N; Yu, Yuefeng; Antheaume, Gabriel; Gordeev, Georgy; Yagodkin, Denis; Elliott, Peter; de Araújo, Daniel B; Sharma, Sangeeta et al. · Nano Lett · 2022

basic_science · Level V

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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 <i>Q</i> 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 (τ<sub>rise</sub> ∼ 135 ns), sensitive (noise-equivalent power = <math xmlns="http://www.w3.org/1998/Math/MathML"><mn>90</mn><mo>⁣</mo><mfrac><mrow><mi>pW</mi></mrow><mrow><mo>√</mo><mi>Hz</mi></mrow></mfrac></math>), and broadband (1.2-3.1 eV, extendable to UV-THz) method provides an attractive alternative to spectroscopic or ellipsometric characterization techniques.