Structure-Dependent Hydrostatic Deformation Potentials of Individual Single-Walled Carbon Nanotubes

The hydrostatic pressure coefficients of interband transition energies of a number of single-walled carbon nanotubes with different chiralities were measured. Optical experiments were performed on debundled, single-walled carbon nanotube suspensions with hydrostatic pressure applied by diamond anvil cells. The pressure coefficients of the band-gap energies are negative and dependent on the nanotube structure, while the second van Hove transitions are much less sensitive to hydrostatic pressure. An empirical equation that relates the pressure coefficients to nanotube structure is presented and discussed.

Figure 1

Absorption spectrum of a SWNT suspension. The inset shows the absorption spectrum in the near infrared region in comparison with a PL spectrum. No PL peak was observed above 1.5 eV (not shown here). The peaks are numbered in order of increasing peak energy.

Figure 2

(a) Absorption spectrum in the near infrared (group $A$) taken at a range of hydrostatic pressures. The curves are vertically offset for clarity. (b) Absorption curves at higher energies (group $B$) as a function of pressure.

Figure 3

Measured linear pressure coefficients as a function of peak energy. The number beside each data point shows the peak number. Numbers in the $E_{11}$ symbols are the value of $n-m$. The dashed lines connect families with equal $n-m$ values. The inset shows the dependence given by Eq. (1) for all $E_{11}$ points.