Crystal-encapsulation-induced band-structure change in single-walled carbon nanotubes: Photoluminescence and Raman spectra

We report studies of the modification of the band structure of single-walled carbon nanotubes through encapsulation of the inorganic material manganese ditelluride (MnTe2). Using photoluminescence excitation mapping we show that this leads to a global reduction of their first and second band gap energies by a similar percentage (up to 3.8%). We interpret this as due to the additional screening which causes a change in the internal dielectric constant and a possible lowering of the carbon-carbon transfer integrals. The shifts increase with increasing tube diameter due to the increased quantity of filled materials.