Correlation between Raman spectroscopy and electron microscopy on individual carbon nanotubes and peapods

Viac o knihe

This thesis investigates the filling of carbon nanotubes (CNTs) grown by chemical vapor deposition (CVD) with guest molecules directly on substrates, necessitating characterization of the CNTs post-synthesis. High-resolution TEM and Raman spectroscopy reveal that the diameter distribution and number of layers of as-grown CNTs are influenced by the growth temperature (TCVD). Notably, HRTEM measurements can induce defects, even at low electron energies (80 keV), while Raman spectroscopy remains non-destructive for individual CNTs at low laser intensities (P < 0.5mW). This encouraged a correlation between HRTEM and Raman spectroscopy, leading to the first experimental proof of radial phonon-coupling in a multi-walled CNT and a bundle of single-walled CNTs, validated by a simple numeric model. The width of resonance profiles of radial Raman modes allows for the identification of individual single-walled CNTs, those within bundles, or layers of multi-walled CNTs, facilitating the determination of inter-molecular structures without damaging the CNTs. Additionally, resonant Raman spectroscopy offers crucial insights into the electronic structure of CNTs, vital for future quantum transport measurements. The thesis also explores the synthesis of peapods—CNTs filled with fullerene molecules like C60—detailing the characterization of CNTs after each synthesis step, particularly the opening of as-grown CNTs. A UHV chamber was constructed