In situ characterization of block copolymer ordering on chemically nanopatterned surfaces by time-resolved small angle x-ray scattering

Abstract

The assembly of lamella-forming block copolymer blend thin films on chemically nanopatterned striped surfaces was monitored in real time with small angle x-ray scattering (SAXS) in transmission mode. The strongest diffraction from the assembled grating structure was detected after 4.5min of annealing as the temperature was ramped from 100to240°C at a rate of about 20°C∕min. Real-space images were also obtained from samples annealed for specific times using top-down scanning electron microscopy (SEM) and this identified structures formed during annealing that are unique to the block copolymer blends. The data are compared to previously reported SEM and molecular simulation studies with pure block copolymers. Because it can be used in real time and probes the entire film thickness, transmission SAXS proved to be a useful tool for better understanding the block copolymer annealing process.

Mechanism and dynamics of block copolymer directed assembly with density multiplication on chemically patterned surfaces

“…First, the appearance and disappearance of the scattering peak at 100 nm ͑L s ͒ was a unique behavior of directed assembly of block copolymer with density multiplication, and it was not observed in directed assembly on one-to-one chemical patterns. 31 Second, for both one-to-one directed assembly and for directed assembly with density multiplication ͑L s / L o = 1 and =2, respec-tively͒, dotlike PS domains were observed at the free surface during the early stage of annealing, then coalesced to form linear domains, and eventually, with longer annealing times, these linear domains were ordered and registered with the chemical pattern. Without density multiplication, the dynamics of directed assembly consisted mainly of the coalescence of the domains into linear domains and the registration of the linear domains with the underlying chemical pattern.…”

“…of block copolymer with density multiplication was complex, compared with that on a one-to-one chemical pattern ͑L s = L o ͒. 31 The in situ ͑t Ͻ 1 h͒ scattering intensity of the first-order characteristic peak of 50 nm decreased continuously. We attributed this to the degradation of P͑S-b-MMA͒ by the x rays.…”

“…Formation of hexagonally close-packed polystyrene ͑PS͒ domains, coalescence of the PS domains to linear PS domains that were not fully registered with the underlying chemical pattern, and registration of the linear PS domains with the chemical pattern, were the distinct stages of block copolymer directed assembly that they identified. In addition, Stuen et al 31 used in situ coherent small angle x-ray scattering ͑SAXS͒ to ex-perimentally probe the three-dimensional dynamics of directed assembly of block copolymer-homopolymer ternary blends. In the work we present here, we used in situ SAXS, top-down scanning electron microscopy ͑SEM͒, and Monte Carlo molecular simulation to monitor and characterize the dynamics of the directed assembly of block copolymers with density multiplication on chemical patterns.…”

Block copolymer thin films: Characterizing nanostructure evolution with in situ X-ray and neutron scattering

“…WAXS typically measures scattering from a q of approximately 10 -2 Å -1 to 10 1 Å -1 (nm to Å size scale analysis) [97][98][99]. Using in situ SAXS and WAXS during thermal annealing, BCP domain rearrangement has been studied on chemically-patterned substrates [100,101], during SVA [102], during electric field exposure [103,104], and upon drying after film casting [54,[105][106][107][108]. Notably, SAXS and WAXS examinations of BCP thin films are limited by the relatively small scattering volumes, the potential for radiation damage to the film, and inadvertent structural reorganization from sample interactions with X-rays [111][112][113].…”