Surface modification of polyimide films via low-energy argon ion irradiation: A comprehensive XPS analysis

This research presents an eco-friendly technique for modifying polyimide (PI) films using low-energy argon (Ar⁺) ion irradiation at 200 and 500 eV, enabling precise patterning of micro-structured surfaces. The study investigates surface modifications and initial carbonization processes through X-ray Photoelectron Spectroscopy (XPS), meticulously controlling irradiation times between 0 and 90 sec. The XPS results revealed clear shifts in the binding energies of carbon, oxygen, and nitrogen, indicating an increase in carbon content and a decrease in oxygen and nitrogen levels, leading to significant modifications of the PI films. At 200 eV, XPS demonstrated subtle shifts in the binding energies of C 1s, O 1s, and N 1s spectra, indicating slight surface changes that do not reach the point of carbonization. PI films exposed to 500 eV Ar⁺ ion for varying durations exhibited significant surface alterations. After irradiation, the peaks in the C 1s and O 1s spectra shifted to higher energies, with a decrease in C–O peak intensity and an increase in C–C/C[dbnd]C peak intensity. Additionally, new peaks such as C–OH, C–O (hexa) and graphitic-N emerged, indicating bond breaking and the formation of new chemical bonds. These results suggest the onset of carbonization, transforming the surface by integrating new functional groups. These modifications enhance the polyimide's surface properties, potentially improving its applicability in high-performance environments requiring specific chemical functionalities. This study underscores the efficacy of Ar⁺ ion irradiation in precisely engineering polymer surfaces for advanced technological applications.