Hollow interior structure of spin-coated polymer thin films revealed by ToF-SIMS three-dimensional imaging

Surface patterns were observed on spin-coated poly(bisphenol A decane ether) (BA-C10) films prepared with chloroform and tetrahydrofuran as the solvents. The interior structure of these surface patterns were analyzed using a timeof-flight secondary ion mass spectrometry (ToF-SIMS) equipped with a bismuth cluster source for ion imaging and a C₆₀⁺ cluster source for depth profiling. For the first time, the surface patterns have been shown to be hollow rather than solid using ToF-SIMS three-dimensional (3D) analysis and optical techniques. Moreover, the microarea depth profiling analysis indicated that the hollow structure was sandwiched between two polymer layers rather than sitting on the substrate. The height of the hollow structure and the thicknesses of the polymer layers above and below the hollow structure were also estimated from the depth profiling results.