Selective modification of aligned carbon nanotubes by N2 plasma and their diode behavior

Abstract

Aligned carbon nanotubes made by pyrolysis of ferrocene are selectively treated with N₂ plasma at various durations. Raman spectra reveal that polar bonds form at treated regions and result in increased Raman breathing mode. XPS support Raman and verify the C–O/C–N formations in carbon lattices. Electrical measurements show an unipolar p-type character as probes are placed in contact with untreated regions of nanotubes. Reposition of probes at untreated and treated regions respectively produces a current–voltage profile that resembles a p–n junction diode with forward current reaching a value as high as 100 mA at 3 V. Ab initio calculations confirm the on-tube junction and creation of a donor state is owing to C–N formations.