Paper AS-WeA2
A New Cluster Ion Beam for Advanced Molecular Depth Profiling of Polymers by TOF-SIMS

Wednesday, October 20, 2010, 2:20 pm, Room Cochiti

The introduction of C₆₀⁺ as a sputter beam for TOF-SIMS made it possible to acquire molecular depth profiles on a wide variety of polymers. Previous studies by many different groups have demonstrated that not all polymers can be successfully depth profiled and that certain classes of polymers undergo sputter-induced chemical reduction when bombarded by C₆₀⁺ ions. If the polymer sputter yield is not high enough, the subsurface sputter-induced damage will accumulate as a function of sputter ion dose and the secondary molecular ion signals will not be stable. A number of different analytical parameters have been previously explored in attempts to improve depth profiling of these difficult polymers including sample temperature, beam energy, and incidence angle. We reported last year that glancing C₆₀⁺ incidence angle (76° from surface normal) significantly improved the ability to depth profile polycarbonate and polystyrene, which were previously unsuccessful at a typical incidence angle of 48°. However, even under these optimized conditions, the depth profiles eventually fail after several hundred nanometers due to accumulated sputter damage to the polymer and a concurrent reduction of the secondary ion and sputter yields. In the present study, we report the efficacy of an argon gas cluster ion beam (GCIB) for steady-state molecular depth profiling the same polymer systems. Depth profiles using different GCIB experimental conditions will be reported and compared to C₆₀⁺ depth profiles acquired under optimized conditions.