Characterization of ion radiation-induced damage in polyimide by wavelength-scanning and dual-wavelength laser photoacoustic spectroscopy

In this paper, photoacoustic spectroscopy (PAS) was presented to characterize the ion radiation-induced damage in the polyimide (PI). We demonstrated a mathematical model of monochromatic light excited photoacoustic (PA) pressure in ion radiation damaged PI. A dual-wavelength PA relative amplitude difference linear dependence on ion irradiation fluence was proposed to quantitatively determine the ion radiation damage in PI. The ion radiation-induced optical absorption modifications of PI films radiated by different fluence of ions were measured by means of wavelength-scanning (400 nm-800 nm) PAS and dual-wavelength (405 nm, 808 nm) laser PAS methods. The results indicated that the optical absorption of PI material was obviously enhanced with the increase of radiated ion fluence. The PA relative amplitude difference induced by laser at the wavelength of 405 nm and 808 nm showed approximate linear dependence on the radiation fluence of nitrogen ions, which was a good agreement with the theoretical model. PAS approaches have the merits of high specificity and sensitivity to the ion radiation-induced damage in PI material and provide a reliable tool to evaluate the damage quantitatively.