C ₆₀ molecular depth profiling of bilayered polymer films using ToF‐SIMS

Dual‐beam time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) (sputter ion, 15 keV C 60 + ; analysis ion, 15 keV Ga + ) was used to depth profile two types of spin cast bilayered films, Poly(vinyl pyrrolidone) (PVP)/poly(methyl methacrylate) (PMMA) and poly(4‐vinyl pyridine) (P4VP)/PMMA on silicon substrates. Positive and negative ion molecular depth profiles were obtained and compared on the basis of the stability of the characteristic secondary ion intensities, the sputter rates of the polymers, and the interface widths between the polymer layers and at the silicon substrate. The sputter rates of the top polymer in the bilayered films were typically the same as for the corresponding single‐layer films. However, the presence of a P4VP top layer significantly decreased the sputter rate of the underlying PMMA films. Typical interface widths between adjacent polymer layers were less than the polymer‐silicon interface widths. Additionally, the bilayered films with the P4VP on the outermost surface had higher interface widths.