Enhanced photoluminescence in air-suspended carbon nanotubes by oxygen doping

摘要

We report photoluminescence (PL) imaging and spectroscopy of air-suspended carbon nanotubes (CNTs) before and after exposure to a brief (20 s) UV/ozone treatment. These spectra show enhanced PL intensities in 10 out of 11 nanotubes that were measured, by as much as 5-fold. This enhancement in the luminescence efficiency is caused by oxygen defects which trap excitons. We also observe an average 3-fold increase in the D-band Raman intensity further indicating the creation of defects. Previous demonstrations of oxygen doping have been carried out on surfactant-coated carbon nanotubes dissolved in solution, thus requiring substantial longer ozone/UV exposure times (～15 h). Here, the ozone treatment is more efficient because of the surface exposure of the air-suspended CNTs. In addition to enhanced PL intensities, we observe narrowing of the emission linewidth by 3-10nm. This ability to control and engineer defects in CNTs is important for realizing several optoelectronic applications such as light-emitting diodes and single photon sources.