Local control of microdomain orientation in diblock copolymer thin films with electric fields

Science

Volumn 273, Issue 5277, 1996, Pages 931-933

  Morkved, T L ^a   Lu, M ^a   Urbas, A M ^a   Ehrichs, E E ^a,c   Jaeger, H M ^a   Mansky, P ^b   Russell, T P ^b  

^a UNIVERSITY OF CHICAGO   (United States)

^b IBM ALMADEN RESEARCH CENTER   (United States)

^c ADVANCED MICRO DEVICES   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; ELECTRIC FIELD; FILM; POLYMERIZATION; PRIORITY JOURNAL; STRUCTURE ANALYSIS;

EID: 0029790896     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.273.5277.931     Document Type: Article

References (36)

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22. Our substrates consisted of a 100-nm-thick silicon nitride layer deposited onto a silicon wafer. The silicon was selectively elched away from the backside of the wafer under small rectangular areas, providing self-supporting, transparent silicon nitride membranes with lateral dimensions of 60 μm. We fabricated planar electrodes with gap spacings of 4 μm on top of the silicon nitride within the window areas using optical or electron-beam lithography followed by evaporation of 25-nm chromium. Small gold wires were attached with silver epoxy and connected to a programmable voltage source.
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24. χN∼30, putting us in the strong segregation limit. See T. P. Russell, R. P. Hjelm, P. A. Seeger, Macromolecules 23, 890 (1990); T. P. Russell, ibid. 26, 5819 (1993).
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28. min are the order parameters obtained by image processing from a perfectly aligned region containing no defects and from an unaligned sample annealed without an applied E field, respectively.
29. E. V. Gurovich [Macromolecules 27, 7063 (1994)] proposed that alignment in copolymers is due to field-induced changes in the coil conformations. Because the anisotropic part of the polarizability of most monomers is much smaller than the average polarizability, this mechanism can be neglected for nonpolar systems compared to the effect treated by Amundson et al. [see A. Onuki and J. Fukuda, Macromolecules 28, 8788 (1995)]. Even though PMMA does contain permanent dipoles, we can estimate their contribution and find it not significant [see also the discussion in (10)].
30. E. V. Gurovich [Macromolecules 27, 7063 (1994)] proposed that alignment in copolymers is due to field-induced changes in the coil conformations. Because the anisotropic part of the polarizability of most monomers is much smaller than the average polarizability, this mechanism can be neglected for nonpolar systems compared to the effect treated by Amundson et al. [see A. Onuki and J. Fukuda, Macromolecules 28, 8788 (1995)]. Even though PMMA does contain permanent dipoles, we can estimate their contribution and find it not significant [see also the discussion in (10)].
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32. R. F. Boyer, in Encyclopedia of Polymer Science and Technology (Intersciences, New York, 1970), vol. 13, pp. 251-277; N. G. McCrum, B. E. Read, G. Williams, Anelastic and Dielectric Effects in Polymeric Solids (Wiley, New York, 1967), p. 264.
33. 2/ε, in centimeter-gram-second units, where the coefficient γ depends on the details of the domain geometry. In the case of cylindrical domains, as in our samples. γ = 1/9.
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35. Systematic studies of the effect of changing the annealing conditions are in progress. The degree of alignment in E fields <30 kV/cm might improve with different annealing conditions, leading to a reduction in the saturation field for the order parameter S(E). However, improvements in the ordering of unaligned samples under the same conditions are also likely, leading to an increase in the average radius of curvature and a decrease in the curvature energy.
36. We thank T. A. Witten, F. J. Soils, and S. R. Nagel for helpful discussions. Supported in part by the Medical Research Science and Engineering Center program of the National Science Foundation (NSF) under award DMR-9400379. The silicon nitride membranes were fabricated at the National Nanofabrication Facility at Cornell University, which is supported by the National Science Foundation under grant ECS-8619049. H.M.J. acknowledges fellowship support from the David and Lucile Packard Foundation. T.P.R. and P.M. acknowledge the support of the U.S. Department of Energy, Office of Basic Energy Sciences, under contract FG03-88ER-45375.