Local control of the domain orientation in diblock copolymer thin films can be obtained by the application of electric fields on micrometer-length scales. Thin films of an asymmetric polystyrene-polymethylmethacrylate diblock copolymer, with cylindrical polymethylmethacrylate microdomains, were spin-coated onto substrates previously patterned with planar electrodes. The substrates, 100-nanometer-thick silicon nitride membranes, allow direct observation of the electrodes and the copolymer domain structure by transmission electron microscopy. The cylinders aligned parallel to the electric field lines for fields exceeding 30 kilovolts per centimeter, after annealing at 250°C in an inert atmosphere for 24 hours. This technique could find application in nanostructure fabrication.

In this report, we highlight the development of polymers as 1D photonic crystals and subsequently place special emphasis on the activities in self‐assembled block copolymers as a promising platform material for new photonic crystals. We review recent progress, including the use of plasticizer and homopolymer blends of diblock copolymers to increase periodicity and the role of self‐assembly in producing 2D and 3D photonic crystals. The employment of inorganic nanoparticles to increase the dielectric contrast and the application of a biasing field during self‐assembly to control the long‐range domain order and orientation are examined, as well as in‐situ tunable materials via a mechanochromic materials system. Finally, the inherent optical anisotropy of extruded polymer films and side‐chain liquid‐crystalline polymers is shown to provide greater degrees of freedom for further novel optical designs.

been demonstrated. The diameter and the number density of nanowires were controlled by altering the gold layer thickness. The length of nanowires was controlled by adjusting the a-Si layer thickness. The number density of nanowires with rare Au 2 Si nanopea-pods could be controlled by adjusting the growth time, using Au 2 Si as catalytic nucleation sites. The presence of a broad PL peak around 700 nm for Au 2 Si@-SiONW and, exclusively, in SiONWs with rare Au 2 Si has been argued to originate from the non-bridging oxygen present solely in SiONWs. A new, sharp peak around 683 nm in the PL spectrum, observed, exclusively, in the Au 2 Si@SiONW samples, has been assigned to a radiative recombination process related to interband transitions in gold silicide nanosphere pea-podded in the amorphous SiONW containing large defect states. ExperimentalFor the growth of silicon-based nanowires, an a-Si thin film was first deposited on a crystalline silicon [c-Si (100)] substrate with an ion-beam sputtering deposition (IBSD) system. A detailed description of the system has been published elsewhere [24]. The a-Si film thickness was in the range of 70±140 nm; determined by FESEM (JEOL 6700) studies. The gold thin film, as the catalytic layer, was next deposited by dc sputtering (Hitachi E101) with a 20 mA sputtering current and deposition periods ranging from 15 to 300 s. The deposition rate was estimated as 4 nm min ±1 , as determined by thickness measurements of those films, deposited for different durations, by FESEM. Finally, we put the Au/a-Si/ c-Si sample into a quartz tube furnace for thermal annealing at 1030 C in a nitrogen gas (99.9999 %) ambient for~10±30 min. The gas flow rate was maintained at 50 sccm and the pressure of the chamber was maintained at 1 atm.Photonic crystals are being aggressively pursued for their potential to revolutionize optical communication systems and optical computation. [1] The necessary fabrication of large area, well ordered photonic crystals in three dimensions for these applications has proved to be a difficult technological hurdle. Layer-by-layer fabrication, [2] holography, [3] and single step deposition [4] have been used to fabricate high-quality photonic crystals. Researchers have also turned to self-assembly as an approach for creating the large-area ordered arrays in three dimensions that constitute a photonic material. [5±7] We employ a self-assembling block copolymer system to form the double gyroid (DG) morphology at an appropriate length scale to interact with visible light. The optical properties of the poly(styrene-b-isoprene) diblock photonic material are compared with expected reflectivity. The block copolymer is subjected to a UV treatment to remove the isoprene component as a method of modifying the optical properties. This process can serve as the basis for fabricating a three dimensional photonic crystal with a complete photonic bandgap at visible wavelengths from a block copolymer template.Block copolymers (BCPs) offer an alternative means to produce self-assemb...

Block copolymers self-assemble into one-, two-, and three-dimensional periodic equilibrium structures, which can exhibit photonic bandgaps. This paper outlines a methodology for producing photonic crystals at optical length scales from block copolymers. Techniques for enhancing the intrinsic dielectric contrast between the block copolymer domains, as well as increasing the characteristic microdomain distances, and controlling defects are presented. To demonstrate the applicability of this methodology, a self-assembled one-dimensional periodic structure has been fabricated that reflects visible light. The wealth of structures into which block copolymers can assemble and the multiple degrees of freedom that can be built into these materials on the molecular level offer a large parameter space for tailoring new types of photonic crystals at optical length scales.

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