Figures 1 and 2 compare survey scans of PLGA, as received and after sputtering with a standard Ar+ ion beam (Figure 1) and with a C60+ ion beam (Figure 2). The Ar+ ion beam used to sputter PLGA causes a rapid loss in the O signal, which manifests itself as a dramatic change in the C1s region of the spectrum from the polymer (Figure 3). Sputtering with an Ar+ ion beam, shows a dramatic reduction in C-O and O=C-O chemistries and an increase in the C-C signal, as the sample becomes more graphitic in nature. In contrast, Figure 3 also shows that the C region, after C60+ ion bombardment, is almost identical to that of the as-received surface. Figure 4 shows that the intensities of the C and O remain constant throughout the C60+ depth profile through the PLGA.
The second example demonstrates the use of the C60+ ion beam as an efficient polymer surface cleaning tool. In this example, a sample of polytetrafluoroethylene, PTFE, was contaminated with fingerprints. As shown in Figure 5, the C1s spectrum of the as-received surface has a strong hydrocarbon line and smaller oxidized C components, in addition to the expected CF2 line, consistent with PTFE. An attempt to clean off the contamination by the Ar+ ion beam removes the hydrocarbon, but severely damages the fluorocarbon chemistry by partially breaking the -(CF2-CF2)n– chain. In contrast, cleaning this surface with the C60+ ion beam causes almost no damage. The depth profile in Figure 6, plotting two types of carbon (surface hydrocarbon and PTFE) shows the efficiency of contamination removal by the C60+ ion beam and the retention of the structurally significant CF2 signal.
These examples illustrate the excellent prospects for using C60 depth profiling and surface cleaning to analyze samples that would be very difficult to tackle using traditional monatomic sputtering.