Stable doped sp2 C-hybrid nanostructures by reactive ion beam irradiation

Abstract

Boron doping of polyimide precursors yields films, that when ion irradiated produces high aspect ratio nanowires of 15–25 nm diameter of B substituted ∼4 nm sp² C-clusters embedded within polyimide as shown by HRTEM, AFM and electrostatic force EFM. XPS confirmed B substitution within the sp² structures and also showed that the presence of B during the ion induced thermal transformations enhanced N co-substitution, while the G and D Raman bands indicated a high degree of disorder within these C-nanoclusters which increased with atom substitution. Electron transport properties indicated the semiconducting behaviour of the C-nanowire arrays. Impedance spectroscopy separated electron hopping transport within these nanowires from electron tunnelling between neighbouring nanowires. Nanowires were clearly surrounded by an altered polymer interphase region of increased segmental chain mobility and higher dielectric polarisability allowing control of overall electron transport in device applications. This reactive ion beam irradiation route allows separation of chemical doping and synthesis from the nanostructure fabrication, as a new nanotechnology route.