Film Thickness Driven Phase Transition of a Diblock Copolymers with an Order-Order Transition (OOT)

Edward J. Kramer, University of California-Santa Barbara, DMR 0704539

Thin films with a gradient in the film thickness t of diblock copolymers (BCP) with an OOT from spherical domains at temperature T>140°C to cylinder domains for T<140 °C were prepared on silicon wafers. Samples were annealed both above (165 °C) and below (125 °C) the OOT and the structure was characterized by both AFM and grazing incidence small angle X-ray scattering (GISAXS). For annealing temperatures both above and below the OOT, the film has spherical domains when t < t* = 46 nm for an ideal monolayer of cylinders, then remains cylindrical as t is further increased. In films of cylinder dopmains however spheres are often present at the cores of dislocations and disclinations where the elastic strain is significant. These results demonstrate that 1) the morphology a BCP in the bulk is not a reliable guide to its thin film morphology and 2) that BCP with a composition near an OOT are poor candidates for BCP lithography because very different morphologies have nearly equal free energies.

GISAXS for films of various tAFM phase images for BCP films: left, t = 35nm, right, t = 67nm

Film Thickness Driven Phase Transition of a Diblock Copolymers with an Order-Order Transition (OOT)

Edward J. Kramer, University of California-Santa Barbara, DMR 0704539

Karen Sohn will defend her PhD thesis in September of 2008 and then move to the Medical/Surgical group at Becton Dickinson where she will work on their green initiative to evaluate materials for use in BD devices.

Terence Choy performing the fractional precipitation in the Polymer Charcterizaton Lab in the MRL at UCSB.

Terence Choy, now a Ph.D. student at UC Berkeley in the group of Jean Fréchet, was a summer intern in the NSF RISE program while he was an undergraduate at Columbia. Terence fractionated the diblock copolymer from a commercial polymer blend provided by Kraton. He used fractional precipitation to purify both diblock and triblock from the blend that are each 95% pure.

Karen Sohn taking AFM measurements in the Microscopy Lab at UCSB.

This research has resulted in collaborations with Drs. Brian Berry and Alamgir Karim of the Nanostructured Materials group at NIST as well as with Drs. Jin Wang and Michael Sprung of the Advanced Photon Source at Argonne National Lab

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