Multi-Frequency EPR and DC Conductivity of Itinerant Spins in Single-Wall Carbon Nanotubes

• Published in: Applied magnetic resonance 2010, Vol.37 (1-4), p.595-603
• Main Authors: Dinse, Klaus-Peter, van Tol, Johan, Ozarowski, Andrew, Corzilius, Björn
• Format: Article
• Language: English
• Subjects: Atoms and Molecules in Strong Fields; Chemical vapor deposition; Deoxygenation; Direct current; Electron paramagnetic resonance; Electrons; Experiments; Laser Matter Interaction; Low temperature; Microwave frequencies; Organic Chemistry; Physical Chemistry; Physics; Physics and Astronomy; Room temperature; Single wall carbon nanotubes; Solid State Physics; Spectroscopy/Spectrometry; Temperature; Temperature dependence
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/s00723-009-0084-5

Sealed, deoxygenated single-wall carbon nanotubes show two characteristic electron paramagnetic resonance (EPR) signals at g  = 2 . 07 and g  = 2 . 00 in the temperature range from 300 to 50 K. Reversible interconversion between both components was observed. The large g -shift and the temperature dependence of the EPR susceptibility of the g  = 2 . 07 signal indicate that this signal can be attributed to itinerant spins. At low temperatures only the g  = 2 . 00 signal remained, which could be further characterized using microwave frequencies up to 320 GHz. The direct current conductivity of a partially aligned sample was also measured. The room temperature value was estimated as 0.7 (Ωcm) −1 . The observed temperature dependence can be described by assuming temperature-activated hopping in a small-gap semiconductor with an activation energy of 3.5 meV, similar to the characteristics of the previously measured 9.4 GHz microwave conductivity.