Carbon nanotubes have attracted tremendous attention due their unique properties and promising applications. Carbon nanotubes exhibit large variation in the structure which determines their physical properties.
Here conductivity and field emission of carbon nanotubes (CNTs) grown by chemical vapor deposition (CVD) and supercritical fluid (SCF) methods were analysed and compared in identical conditions by using a scanning tunneling microscope that is compatible with a transmission electron microscope. The structure of the nanotubes was altered by using different catalysts and growth conditions. Electrical properties for tube, "bamboo" like CNTs and nanotubes with a multikink structure were determined.
The I(V) characteristics of the nanotubes were measured in two contact configurations. Nanotubes with "bamboo" like structures grown by a CVD method exhibit substantially higher resistance and nonlinearities in I(V) characteristics in comparison to tube like CNTs. SCF grown nanotubes exhibit nonlinear and slightly nonsymmetrical characteristics which may be caused by presence of molecular junctions inside the nanotubes. Nanotubes grown by the SCF method exhibited rectifying effect.
Nanotube failure currents and voltages were determined and compared. Notably bamboo like nanotubes break at higher voltages in comparison to tube like nanotubes and can be used for high voltage applications.
Field emission characteristics for all CNTs were determined and compared to the Fowler-Nordheim equation. CNT failure emission currents and voltages were determined for all types of CNT. The dependence of field emission properties on the nanotube structure is discussed.