TOF-SIMS depth profiling of deuterated polystyrene-block-poly(n-propyl methacrylate) diblock copolymer films

Abstract

A surface-induced orientation of symmetric, deuterated polystyrene/poly(propyl methacrylate) diblock copolymers, dPS-PPrMA with different molecular weights (M-n = 135000, 119600, and 75 300) was investigated using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Elemental depth profiles obtained in the negative ion mode by a Cs+ primary ion beam demonstrate variations in hydrogen, deuterium, carbon, oxygen, and hydrocarbons within the diblock copolymer according to the depth. Solution casting films of the copolymers with thicknesses of 700 and 2100 angstrom exhibited no preferential orientation of the microdomain morphology with respect to the surface at room temperature. Annealing the copolymer films at 215 degrees C for 4 h produced a dramatic orientation of the microdomains parallel to the surface of the film. This preferential alignment provided regular oscillation in the composition of both blocks, which continued through the entire film. The periodicity as determined from a depth profile of TOF-SIMS showed good agreement with the results of small-angle X-ray scattering. Positive and negative ion molecular depth profiles by a C-60(+) cluster ion beam also provide information pertaining to the lower disorder order transition (LDOT) behavior of the dPS-PPrMA copolymer. Depth profile results indicate a PPrMA layer preferentially located at the copolymer/silicon substrate interface. The microdomain separation processes of dPS-PPrMA were investigated as a function of the annealing temperature and time. Copyright (C) 2010 John Wiley & Sons, Ltd.