Self-assembly is an effective strategy for the creation of periodic structures at the nanoscale. However, because microelectronic devices use free-form design principles, the insertion point of self-assembling materials into existing nanomanufacturing processes is unclear. We directed ternary blends of diblock copolymers and homopolymers that naturally form periodic arrays to assemble into nonregular device-oriented structures on chemically nanopatterned substrates. Redistribution of homopolymer facilitates the defect-free assembly in locations where the domain dimensions deviate substantially from those formed in the bulk. The ability to pattern nonregular structures using self-assembling materials creates new opportunities for nanoscale manufacturing.

An x-ray interferometer has been developed that uses two transmission phase gratings to analyze wave front distortions in the hard x-ray range. The interferometer is insensitive to mechanical drift and vibrations, and it is tunable over a wide range of photon energies. This setup was used for differential phase contrast imaging of low-absorbing test objects. We obtained micrographs with moiré fringes of good visibility, which revealed the local phase shift gradient caused by the objects. A comparison with numerically simulated images indicates that quantitative analysis of unknown phase objects is possible.

Block-copolymer lithography refers to the use of the selfassembling domain structure in thin films of block copolymers to template dense patterns into materials at the scale of 5±50 nm. Applications of this technology include the fabrication of quantum dots, [1,2] photonic crystals, [3,4] nanowires, [5,6] magnetic-storage media, [7] silicon capacitors, [8] and flash memory devices. [9,10] The major challenges facing block-copolymer lithography and its potential impact with respect to the fabrication of nanometer-scale devices is the emulation of the following essential attributes of current photolithographic materials and processes: 1) nearly perfect patterning over very large areas, and 2) registration of the pattern with features of the underlying substrate. Some of the strategies that are pursued in order to increase the length scale over which the domains in block-copolymer films are desirably oriented and ordered include graphoepitaxy, [11±13] in-plane electric fields, [14] directional solidification, [15] solvent evaporation, [16] and chemical surface patterns.[17] Recently we demonstrated that perpendicularly oriented lamellar domains in blockcopolymer films could be induced to assemble such that the ordering of domains was perfect over arbitrarily large areas and each domain was registered with the underlying substrate.[17] Imaging layers were patterned with advanced lithography in order to produce stripes of different chemical functionality. Adjacent stripes exhibited neutral wetting and preferential wetting towards the blocks of the copolymer, and if the period of the stripes, L s , closely matched the bulk lamellar period of the block copolymer, L o , then the domain structure in the film self-assembled in an epitaxial manner with respect to the chemically nanopatterned substrate. Here we demonstrate the process latitude of epitaxial block-copolymer lithography, that is, the range of dimensions of features (or periodicity of structures) that can be patterned with perfection using the same composition and molecular weight block copolymer, is significantly improved by increasing the contrast in interfacial energy or wetting behavior between adjacent chemically patterned regions onto which the polymer films self-assemble. The impact of incommensurate periods, L s and L o , on domain ordering, and the types of defects that occur due to incommensurability have been investigated both experimentally [18±20] and theoretically. [21±27] In epitaxial assembly of lamellar structures onto neutral/preferential wetting striped surfaces consisting of self-assembled monolayers, perfect epitaxial assembly occurred only if L s was within a few percent of L o .[17] If L s = 45 nm and L o = 48 nm, pairs of dislocation defects were observed in the compressed lamellae, and if L s was greater than 52.5 nm and L o was 48 nm, herring-bone defects, tilted domains, and domains unregistered with the surface pattern were observed. Rockford et al. [18] investigated the structure of 30 nm thick films of block copolymers of differe...