화학공학소재연구정보센터
Journal of Chemical Physics, Vol.114, No.19, 8573-8582, 2001
Electron transport across fractal-like nanocrystalline clusters in N+ ion-beam induced poly(phenylene oxide)
Nanocrystalline carbonaceous cluster evolution and electron transport in the N+ beam induced spin coated poly(2,6-dimethyl-1,4-phenylene oxide) thin films as a function of ion fluence has been investigated. Following Robertson's model and electron diffraction, the narrow optical band gaps were explained in terms of polyaromatic, single crystalline graphitelike clusters. With a threshold fluence of 1x10(15) ions/cm(2) for cluster growth, the size of the clusters ranged from 2 to 50 nm with the number of aromatic rings varying between 20 and 170 over the entire fluence range upto 8x10(16) ions/cm(2). A molecular reconstruction/self organization has been envisaged as a possible clue to the above structure evolution upon a critical energy density transferred to the 53 nm implanted layer. Transmission electron microscopy study of fractal scaling in the nanoparticle aggregates revealed a fractal dimension of 1.37 +/-0.02 with the growth process to follow a diffusion limited aggregation model. Electrical conductivity data are explained in terms of a phase transition from an insulating state to a trap controlled hopping conduction of charge carriers between localized states on the backbone cluster with a backbone fractal exponent similar to3.