Structure and electronic properties of potassium-doped single-wall carbon nanotubes

The structure and electronic properties of potassium-doped single-wall carbon nanotubes have been studied by conduction electron spin resonance, conductivity $(\ensuremath{\sigma}),$ and x-ray diffraction (XRD), using in situ electrochemical methods. The spin susceptibility ${\ensuremath{\chi}}_{P}$ of the K-saturated phase is independent of temperature; a lower bound is $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\mathrm{e}\mathrm{m}\mathrm{u}/\mathrm{g}.$ At 300 K both $\ensuremath{\sigma}$ and ${\ensuremath{\chi}}_{P}$ increase monotonically and reversibly with K/C. The spin relaxation rate and g factor do not change with doping, and XRD reveals an irreversible loss of crystallinity upon doping. We propose an inhomogeneous doping model to explain these results.