Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways

TL;DR

This study systematically analyzes how various parameters affect optical motion detection efficiency in 2D nanostructures, providing design guidelines for optimized nanomechanical systems using interferometry.

Contribution

It introduces a Fresnel-law-based model to quantify motion responsivity in 2D nanostructures and identifies optimal material and device configurations for enhanced detection.

Findings

MoS2 exhibits highest responsivity among tested materials.

Vacuum gap in 300nm-oxide substrate is near optimal for responsivity.

Responsivity depends on material type, layer number, gap, oxide thickness, and wavelength.

Abstract

Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405nm). We also find that the vacuum gap resulting from the widely used 300nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout.