 Characterizing the Order in 2D Block Copolymer Single Crystals Edward J. Kramer, University of California-Santa Barbara, DMR D single crystal monolayers of block copolymer spheres are of interest to pattern arrays with nanoscale periodicity. Theoretically the order in such crystals is limited by thermal excitation of long wavelength phonons, the severity of this limitation depending inversely on the 2D shear modulus of the crystal. To test these ideas we have templated the formation of highly oriented single crystals in arrays of 12  m wide hexagonal wells, 30 nm deep, that span the entire area of 5 cm diameter silicon wafers. The structure of the aligned 2D crystals was determined by grazing incidence small angle X-ray scattering (GISAXS), resulting in single crystal diffraction patterns. From line shape analysis of the diffraction peaks, we found that the translational order decays with distance from a given sphere as a power law with a decay exponent of -0.2, consistent with the Kosterlitz-Thouless-Halperin-Nelson-Young theory for a 2D crystal with a 2D shear modulus of 2  N/m. This value is equivalent to a 3D shear modulus of 9.2 kPa and is in good agreement with predictions from self-consistent mean field simulations. G.E. Stein. E.J. Kramer, X. Li. J. Wang Phys. Rev. Lett. 98, (2007) Array of hexagonal wells on silicon used to template 2D block copolymer single crystals GISAXS geometry. Diffraction data are obtained as the hexagonal well array is rotated in increments of  as small as 0.1° Single crystal diffraction pattern from block copolymer in a set of 12  m wide wells. Intensity scale is logarithmic.

Broader Aspects of Research Accomplishments New graduate students joined this project in January Pictured below is Adetunji Onikoyi, who is a first year graduate student in Chemical Engineering at UCSB. He comes to us from the University of Houston (ChE) where he did undergraduate research with Professor Ramanan Krishnamoorti. “Tunji” will construct still smaller wells on silicon surfaces using electron beam lithography in order to more closely confine the block copolymers laterally. We expect this closer confinement to decrease the decay exponent and improve the translational order in the wells. We are in discussions with Joy Cheng and Ho-Cheol Kim from IBM-Almaden for Tunji to have access also to some of their advanced optical lithography facilities for producing templating structures in silicon. “Tunji” Onikoyi resealing one of our high vacuum annealing ovens Gila Stein checking the alignment of her 2D block copolymer single crystal at beam line XOR-8 of the Advanced Photon Source at Argonne National Lab where she carried out her GISAXS experiments. Gila Stein won a prestigious NRC Postdoctoral Fellowship at NIST where she is working with Alex Liddle at the Center for Nanoscale Science and Technology. She defended her outstanding PhD thesis at the end of October 2006 and will be interviewing for faculty positions in Chemical Engineering over the coming year with the idea of starting her career in academia in Fall of 2008 or Spring Her research achievements mark her as one of the most promising polymer scientists and engineers of her generation. E. J. Kramer, University of California-Santa Barbara, DMR