Depth profiling of lamella-phase diblock copolymers using SIMS

Abstract

The morphology from symmetric diblock copolymers of poly(styrene-b-propylmethacrylate) (PS-PPrMA), where polystyrene (PS) block was perdeuterated near the copolymer/air and copolymer/substrate interfaces and in the bulk, was characterized by using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Elemental depth profiles measured 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. The annealed deuterated poly(styrene-b-propylmethacrylate) (dPS-PPrMA) copolymer samples showed a decrease in the deuterated PS secondary ion peak intensity as compared to the as-cast samples. TOF-SIMS depth profiling was obtained for the lamellar morphology of dPS-PPrMA which is found to orient parallel to the surface of the substrate. This preferential orientation resulted in a periodic variation in the composition of each block that continued through the entire copolymer film with thickness of 700 and 2100 angstrom. Temperature-dependent annealing studies on dPS-PPrMA thin film on the silicon substrates were performed to investigate the lower critical ordering transition (LCOT) properties of diblock copolymers. Copyright (C) 2010 John Wiley & Sons, Ltd.