Pressure coefficients of Raman modes of carbon nanotubes resolved by chirality: Environmental effect on graphene sheet

TL;DR

This study investigates how environmental factors influence the pressure coefficients of Raman modes in carbon nanotubes and graphene, revealing significant environmental effects on vibrational properties under high pressure.

Contribution

It provides a detailed analysis of environmental effects on Raman mode pressure coefficients, resolving the influence by chirality and diameter in carbon nanotubes and graphene.

Findings

Environmental effects on radial breathing modes are largely environment-independent.

G-mode pressure coefficients vary with diameter, aligning with the thick-wall tube model.

Strong environmental effects are observed on the G-mode pressure coefficients.

Abstract

Studies of the mechanical properties of single-walled carbon nanotubes are hindered by the availability only of ensembles of tubes with a range of diameters. Tunable Raman excitation spectroscopy picks out identifiable tubes. Under high pressure, the radial breathing mode shows a strong environmental effect shown here to be largely independent of the nature of the environment . For the G-mode, the pressure coefficient varies with diameter consistent with the thick-wall tube model. However, results show an unexpectedly strong environmental effect on the pressure coefficients. Reappraisal of data for graphene and graphite gives the G-mode Grueuneisen parameter gamma = 1.34 and the shear deformation parameter beta = 1.34.