Structure, transport and field-emission properties of compound nanotubes:: CNx vs. BNCx (x<0.1)

Transport and field-emission properties of as-synthesized CNx and BNCx (x < 0.1) multi-walled nanotubes were compared in detail. Individual ropes made of these nanotubes and macrofilms of those were tested. Before measurements, the nanotubes were thoroughly characterized using high-resolution and energy-filtered electron microscopy, electron diffraction and electron-energy-loss spectroscopy. Individual ropes composed of dozens of CNx nanotubes displayed well-defined metallic behavior and low resistivities of similar to10-100 kOmega or less at room temperature, whereas those made of BNCx nanotubes exhibited semiconducting properties and high resistivities of similar to50-300 MOmega. Both types of ropes revealed good fieldemission properties with emitting currents per rope reaching similar to4 muA (CNx) and similar to2 muA (BNCx), albeit the latter ropes severely deteriorated during the field emission. Macrofilms made of randomly oriented CNx or BNC, nanotubes displayed low and similar turn-on fields of similar to2-3 V/mum. 3 mA/cm(2) (BNC,) and 5.5 mA/cm(2) (CNx) current densities were reached at 5.5 V/mum macroscopic fields. At a current density of 0.2-0.4 mA/cm(2) both types of compound nanotubes exhibited equally good emission stability over tens of minutes; by contrast, on increasing the current density to 0.2-0.4 A/cm(2) only CNx films continued to emit steadily, while the field emission from BNCx nanotube films was prone to fast degradation within several tens of seconds, likely due to arcing and/or resistive heating.