Electron transport across fractal-like nanocrsytalline clusters in N~+ ion-beam induced poly(phenylene oxide)

摘要

Nanocrystalline carbonaceous cluster evolution and electron transport in the N+ beam induced sp coated poly(2,6-dimethyl-1,4-phenylene oxide) thin films as a function of ion fluence has bee investigated. Following Robertson's model arid electron diffraction, the narrow optical band gal were explained in terms of polyaromatic, single crystalline graphitelike clusters. With a thresho] fluence of 1 X 1015 ions/cm2 for cluster growth, the size of the clusters ranged from 2 to 50 nm Wi1 the number of aromatic rings varying between 20 and 170 over the entire fluence range upto X 1016 ions/cm2. A molecular reconstruction/self organization has been envisaged as a possible dl to the above structure evolution upon a critical energy density transferred to the 53 nm implante layer. Transmission electrOn mic.roscopystudy of fractal scaling in the nanoparticle aggregatt revealed a fractal dimension of 1.37+-0.02 with the growth process to follow a diffusion limite aggregation model. Electrical conductivity data are explained in terms of a phase transition from a insulating state to a trap controlled hopping conduction of charge carriers between localized state on the backbone cluster with a backbone fractal exponent approx 3.