Organic molecule adsorption effects on air-suspended carbon nanotubes*

Environmental screening effects are large in carbon nanotubes due to their atomically thin nature, and therefore it is possible to control the optical properties with molecular adsorption [1,2]. Here, we investigate adsorption effects of copper phthalocyanine molecules on excitons and trions in air-suspended carbon nanotubes. By averaging the photoluminescence excitation spectra for tubes with the same chiralities, we observe that the exciton emission energy redshifts gradually with molecular deposition thickness. The trion emission is also observed at large deposition amounts, which could be due to charge transfer between the phthalocyanine molecules and carbon nanotubes. Analyzing the spectra for individual tubes, we find a good correlation between the exciton-trion energy separation and the exciton emission energy.

[1] T. Uda, A. Ishii, and Y. K. Kato, ACS Photonics 5, 559 (2018).
[2] T. Uda, S. Tanaka and Y. K. Kato, Appl. Phys. Lett. 113, 121105 (2018).