Control of structures of deposited polymer films by ablation laser wavelength: Polyacrylonitrile at 308, 248, and 193 nm

Extensive control of structures of deposited polymer films has been realized when the films have been prepared on a quartz or KBr substrate by laser ablation of polyacrylonitrile (PAN) with 308 (XeCl), 248 (KrF), and 193 nm (ArF) excimer laser beams, as revealed by scanning electron microscopy, infrared spectroscopy, x-ray photoelectron spectroscopy, electron spin resonance, and x-ray diffraction measurements. The original structure of PAN is essentially retained for the films deposited by ablation at 308 nm. Deformation and elimination of nitrile groups occur for the films prepared by ablation at 248 and 193 nm, respectively. Furthermore, a remarkable power-dependent structural change has been observed at 248 nm; an increase in the laser power has led to ring closure of nitrile groups, resulting in the development of pi-conjugated systems. In addition, a rather high electric conductivity on the order of 10(-2)S cm(-1) has been given to the films deposited by ablation at 248 and 193 nm on reirradiation with lower-power excimer laser beams of 308 nm. (C) 1996 American Institute of Physics.