Fractal nature of (formula presented)-bonded nanocrystalline clusters: a (formula presented) beam-induced phenomenon in poly(2,6-dimethyl-1,4-phenylene oxide)

Formation of nanosized carbonaceous clusters has been investigated in 100 keV (Formula presented) irradiated poly(2,6-dimethyl-1,4-phenylene oxide) [PPO] thin films, using Fourier transform (FT)-Raman, transmission electron microscopy and UV-Vis spectroscopy in the fluence range of (Formula presented) Above a critical fluence of (Formula presented) the energy density transferred to the implanted layer resulted in a molecular construction/self-organization process with the evolution of graphitelike clusters of varying size (Formula presented) Electron diffraction analysis of these clusters shows a close resemblance to the formation of single crystalline graphite phase with a zone axis (Formula presented) The deduced band gaps from the optical spectra using Tauc’s approximation provided information on the electronic structure of the fused hexagonally clustered aromatic rings with varying sizes; the number of the rings varying from (Formula presented) Evidence for the signature of fractal patterns, with dimension (Formula presented) during aggregation of small particlelike clusters in the polymer implanted layer is presented; analysis of the data suggests the growth process to follow a diffusion-limited-aggregation model. © 1999 The American Physical Society.