Study of polymer coatings implanted with high-energy ion beams

In this study, the physicochemical properties of thin films based on linear polymers implanted with ions within an energy range of 50–125 keV and a fluence of 10 ¹ ³–10 ¹ ⁷ cm⁻² were comprehensively investigated. The experimental focus was primarily on positively charged photoresist-based polymer coatings, including polystyrene, PMMA, and FP-resists, which were irradiated with both light ions (N⁺, O⁺) and relatively heavy ions (Ar⁺, Kr⁺). Structural and chemical transformations induced by ion implantation were analyzed using infrared (IR) spectroscopy, electron paramagnetic resonance (EPR), Raman spectroscopy, as well as measurements of optical density, chemical stability, tensile resistance, electrical resistivity, and conductivity. The results revealed that chain scission, cross-linking, and partial aromatization predominated within the polymer matrices under ion irradiation. These processes disrupted the initial amorphous structure of the polymers and led to the formation of carbon-rich, locally ordered graphite-like domains and diamond-like carbon (DLC) phases . As a result of these phase transformations, significant enhancements in the final functional characteristics of the polymer films were observed, including mechanical robustness (tensile strength and adhesion), thermal and chemical resistance, optical absorption coefficient, electrical resistivity, and surface conductivity. Specifically, increases in ion fluence were directly correlated with higher optical density, intensified EPR signals, and the emergence of electrical conductivity, all of which were closely linked to the formation of DLC phases. Further analysis indicated that the final morphology and functional performance of the polymer coatings strongly depend on the ratio of the ion projected range to the film thickness (Rp/h), the atomic mass of the irradiating ions, and the implantation dose. In particular, for films with thicknesses below 200–300 nm, when the ions’ average penetration depth approached or exceeded the film thickness, energy deposition throughout the entire film volume was maximized, thereby promoting extensive structural reorganization. The most pronounced modifications were achieved using relatively heavy ions (Ar⁺, Kr⁺) or gaseous ion mixtures (e.g., N₂⁺/O₂⁺) with energies above 120 keV and fluences within the range of 5 × 10 ¹ ⁵–2 × 10 ¹ ⁶ cm⁻², particularly for polymer films thinner than 300 nm. Under these conditions, the formation of DLC phases was maximized, resulting in optimal mechanical and electrical performance. These findings underscore the high efficiency of ion irradiation techniques for targeted structural and functional modification of polymer materials and establish a robust scientific foundation for their application in nanoelectronics, microelectromechanical systems (MEMS), wear-resistant photomasks, and bioactive surface coatings.

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