Revealing Sub-Surface Vibrational Modes by Atom-Resolved Damping Force Spectroscopy

TL;DR

This paper introduces a noninvasive method using damping signals in atomic force microscopy to map and analyze vibrational modes at the atomic scale within carbon nanotubes, revealing molecular packing and local excitations.

Contribution

It demonstrates atomically resolved damping maps to identify vibrational structures and provides a microscopic model with ab initio calculations for interpretation.

Findings

Damping signals can reveal vibrational modes inside nanotubes.

Atomically resolved damping maps identify molecular packing.

Quantitative interpretation aligns with ab initio calculations.

Abstract

We propose to use the damping signal of an oscillating cantilever in dynamic atomic force microscopy as a noninvasive tool to study the vibrational structure of the substrate. We present atomically resolved maps of damping in carbon nanotube peapods, capable of identifying the location and packing of enclosed Dy@C82 molecules as well as local excitations of vibrational modes inside nanotubes of different diameter. We elucidate the physical origin of damping in a microscopic model and provide quantitative interpretation of the observations by calculating the vibrational spectrum and damping of Dy@C82 inside nanotubes with different diameters using ab initio total energy and molecular dynamics calculations.