Secondary Ion Mass Spectrometry (SIMS) employing an SF5+ polyatomic primary ion source was used to depth profile Poly(methyl methacrylate) (PMMA) at a series of temperatures from -75 oC to 125 oC, where the primary glass transition for PMMA occurs at 105 oC. The depth profile characteristics (e.g. interface widths, sputter rates, damage cross sections, and overall secondary ion stability) were monitored as a function of temperature. It was found that at low temperatures, the secondary ion stability increased considerably. In addition, the interfacial widths were significantly lower. Higher temperatures were typically correlated with increased sputter rates. However the improvements in interfacial widths and overall secondary ion stability were not as prevalent as was observed at low temperatures. The importance of glass transition temperature (Tg) on the depth profile characteristics was also apparent. The resulting PMMA depth profile characteristics were compared with that of poly(lactic acid) (PLA), considered to be one of the more successful cases of polymer depth profiling (very low damage cross-sections, high sputter rates, small interface widths). The resulting interface widths and damage cross sections of PMMA at low temperatures were comparable to PLA at room temperature. These results indicate that temperature is an important parameter in the sputtering of polymeric materials and should be optimized.
Citation: Analytical Chemistry
Pub Type: Journals
AFM, cluster SIMS, depth profile, ESCA, polymer(s), SF5+, SIMS, TOF-SIMS, XPS