Effect of silver ion-induced disorder on morphological, chemical and optical properties of poly (methyl methacrylate)

Ion implantation is a versatile technique to tailor the surface properties of polymers in a controlled manner. In the present study, samples of poly (methyl methacrylate) (PMMA) have been implanted with 400 keV silver (Ag⁺) ion beam to various ion fluences ranging from 5 × 10¹³ to 5 × 10¹⁵ ions/cm². The effect of Ag⁺ ion-induced disorder on morphological, chemical and optical properties of PMMA is analyzed using Atomic Force Microscope (AFM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–Vis) spectroscopy. Furthermore, the electrical conductivity of pristine and implanted PMMA is measured using four probe apparatus. The AFM images revealed the growth of nano-sized grainy structures and hillocks above the surface of implanted PMMA. The FTIR spectra confirmed the modifications in chemical structure of PMMA along with the formation of −C=C− carbon contents. The refractive index, extinction coefficient and photoconductivity of implanted PMMA have been found to increase as a function of ion fluence. Simultaneously, indirect optical band gap is reduced from 3.13 to 0.81 eV at a relatively high fluence (5 × 10¹⁵ ions/cm²). A linear correlation has been established between the band gap and Urbach energies. Moreover, the electrical conductivity of Ag⁺ implanted PMMA has increased from 2.14 × 10⁻¹⁰ (pristine) to 9.6 × 10⁻⁶ S/cm.