Impact Energy Dependence of SF 5+-Induced Damage in Poly (Methyl Methacrylate) Studied Using Time-of-Flight Secondary Ion Mass Spectrometry
M S. Wagner
Ion-induced damage of polymers is a critical factor in the depth profiling of polymer surfaces using polyatomic primary ions. However, little work has been done to characterize the damage accumulation in polymer surfaces under polyatomic ion bombardment. In this study, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS) was used to measure the damage of spin cast poly(methyl methacrylate), PMMA, films under 5 keV Cs + and 2.5 - 8.75 keV SF5+ bombardment. Under 5 keV Cs+ bombardment, the characteristic PMMA secondary ion intensities decreased rapidly with primary ion doses > 5 x 1013 ions/cm2. The characteristic PMMA secondary ion intensities followed a substantially different behavior. The damage profiles of PMMA under SF5+ bombardment contained three distinct regions: a surface transient, an extended quasi-stabilization of the characteristic secondary ion intensities, and the decay of these intensities as the silicon substrate was reached. The PMMA film was stable under SF5+ ion doses up to 4 x 1014 ions/cm2, with the maximum ion dose limited by the thickness of the PMMA film. The sputter rate was linearly correlated with the SF5+ impact energy while the damage to the PMMA film did not vary with the SF5+ impact energy. These results were compared with Monte Carlo (SRIM) calculations of the penetration depth and vacancy production for SF5+ at different impact energies. Since the SF5+ impact energy only affected the sputter rate, selection of the appropriate SF5+ impact energy for polymer depth profiling depends solely on the desired sputter rate.
dual beam depth profiling, PMMA, polyatomic ion beam, SF<sub>5</sub><sup>+</sup>
Impact Energy Dependence of SF <sub>5</sub><sup>+</sup>-Induced Damage in Poly (Methyl Methacrylate) Studied Using Time-of-Flight Secondary Ion Mass Spectrometry, Analytical Chemistry
(Accessed June 5, 2023)