We have exploited the highly-regular microdomain structures formed by block copolymers in the creation of templates for nanoscale lithography—a two-dimensional templating procedure. The chemical differences between the blocks constituting the film can be used to create a mask (for example, by selectively etching away polydiene microdomains with ozone), allowing the block copolymer pattern to be transferred to the underlying substrate through reactive ion etching. We have termed this patented process “block copolymer nanolithography”; it is applicable to a broad range of substrates, and moreover, the mask or patterned substrate can act as a template for the growth of regular arrays of nanodispersed materials. We have successfully patterned Si, Ge, and Si3N4 substrates, and have extended this method to fabricate metal dots and lines, and compound semiconductor quantum dots, as shown in the figure below:

The parallel nature of this method lends itself to the fabrication of large-area arrays; we routinely pattern areas as large as 50 cm2. The individual nanostructures have very narrowly-distributed sizes, controllable through the block copolymer molecular weight; typical diameters are 20 nm with a 30 nm spacing, yielding 300,000 lines per cm, or 1011 dots per cm2. If the block copolymer film is deposited and annealed quiescently, it forms a polygrain structure, which is faithfully replicated in each of the images shown above. For some applications, this polygrain structure is satisfactory, but for others, long-range order of the microdomains is required. For such cases, shear-aligned block copolymer thin films are the templates of choice.
Shear-aligned monolayers of cylinder-forming block copolymer can serve as the template for arrays of metal nanowires, with a pitch of order 50 nm. Like the classic gold wire grids used for polarizing infrared radiation, such metal nanowire arrays will polarize light—but because of their small spacing, they will polarize not only infrared, but visible and ultraviolet (UV) light as well. The principle of polarization is illustrated below:

We have fabricated aluminum nanowire grids with square-centimeter areas, and demonstrated their ability to polarize down to 193 nm. We have also developed a model for their polarization characteristics, which reveals that the polarization of the transmitted light switches near the metal’s plasma frequency. These projects were carried out in collaboration with Professor Paul Chaikin (Physics, Princeton; later, Physics, New York University) and Dr. Douglas Adamson (Princeton Institute for the Science and Technology of Materials).
Supported by the National Science Foundation through the Princeton Center for Complex Materials, and by Toshiba Corporation
Group Members Involved, and Their Project Titles:
Young-Rae Hong PDRA – “Well-Ordered Block Copolymer Thin Films Using Shear-Alignment Techniques”
Josee Vedrine-Pauleus PDRA – “Physics and Technology of Sheared Cylinder-Forming Diblock Copolymer Thin Films”
Miri Park PDRA – “Physics and Technology of Sheared Cylinder-Forming Diblock Copolymer Thin Films”
Vincent Pelletier PhD Phys *05 – “Physics and Technology of Sheared Cylinder-Forming Diblock Copolymer Thin Films”
Dan Angelescu PhD Phys *03 – “Physics and Applications of Diblock Copolymer Thin Films”=
Christopher Harrison PhD Phys *99 – “Long Range Orientation of Block Copolymer Microdomains”
Tom Pickthorn Oxford MEng Materials *06 – “Nanopatterning with Block Copolymer Films”
Relevant Group Publications:
Y.-R. Hong, K. Asakawa, D.H. Adamson, P.M. Chaikin, and R.A. Register, “Silicon Nanowire Grid Polarizer Fabricated from a Shear-Aligned Diblock Copolymer Template”, Opt. Lett., 32, 3125-3127 (2007); also in Virtual J. Nanoscale Sci. Tech., 16(22) (November 26, 2007).
J. Vedrine, Y.-R. Hong, A.P. Marencic, R.A. Register, D.H. Adamson, and P.M. Chaikin, “Large-Area, Ordered Hexagonal Arrays of Nanoscale Holes or Dots from Block Copolymer Templates”, Appl. Phys. Lett., 91, 143110 (2007); also in Virtual J. Nanoscale Sci. Tech., 16(16), (October 15, 2007).
R.A. Register, D.E. Angelescu, V. Pelletier, K. Asakawa, M.W. Wu, D.H. Adamson, and P.M. Chaikin, “Shear-Aligned Block Copolymer Thin Films as Nanofabrication Templates”, J. Photopol. Sci. Technol., 20, 493-498 (2007).
V. Pelletier, K. Asakawa, M.W. Wu, D.H. Adamson, R.A. Register, and P.M. Chaikin, “Aluminum Nanowire Polarizing Grids: Fabrication and Analysis”, Appl. Phys. Lett., 88, 211114 (2006); also in Virtual J. Nanoscale Sci. Tech., 13(23), (June 12, 2006).
M. Park, P.M. Chaikin, R.A. Register, and D.H. Adamson, “Large Area Dense Nanoscale Patterning of Arbitrary Surfaces”, Appl. Phys. Lett., 79, 257-259 (2001).
R.R. Li, P.D. Dapkus, M.E. Thompson, W.G. Jeong, C. Harrison, P.M. Chaikin, R.A. Register, and D.H. Adamson, “Dense Arrays of Ordered GaAs Nanostructures by Selective Area Growth on Substrates Patterned by Block Copolymer Lithography”, Appl. Phys. Lett., 76, 1689-1691 (2000).
C. Harrison, M. Park, R. Register, D. Adamson, P. Mansky, and P. Chaikin, “Method of Nanoscale Patterning and Products Made Thereby”, U.S. Patent 5,948,470, issued September 7, 1999.
C. Harrison, M. Park, P.M. Chaikin, R.A. Register, and D.H. Adamson, “Lithography with a Mask of Block Copolymer Microstructures”, J. Vacuum Sci. Technol. B, 16, 544-552 (1998).
M. Park, C. Harrison, P.M. Chaikin, R.A. Register, and D.H. Adamson, “Block Copolymer Lithography: Periodic Arrays of ~ 1011 Holes in 1 Square Centimeter”, Science, 276, 1401-1404 (1997).