Construction of carbon micropattern and nanostructure by ion beam-irradiation of vapor-deposited polycyclic aromatic compounds

The micropatterns and nanostructures of conducting carbonaceous materials were generated by ion beam-irradiation of several polycyclic aromatic compounds that were rapidly evaporated onto substrates under vacuum. Evaporation of the compounds gave either smooth films by direct crystallization of the vapors onto substrates or rugged films by condensation of the vapors onto substrates followed by the crystallization. Ion beam-irradiation of the resultant films caused the development of inter- and intra-molecular aromatic rings accompanying the detachment of hydrogen and hetero atoms. Irradiation with a 200 keV N+ ion beam to a dose of more than 1016 ions/cm2 converted the films to carbonaceous materials with the electrical conductivity comparable to graphite. A desired micropattern of conducting carbon was obtained by irradiating the films through a mask. Irradiation of the rugged films of 1-aminoanthraquinone, acenaphthenequinone and 2,4,6-tri(2-pyridyl)-1,3,5-triazine caused significant volume contraction that was induced by the detachment of hetero atoms. The contraction proceeded while keeping inter-molecular connections with each other, so that the resultant films showed high surface area with nanoscale carbon networks.