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Two concepts of vertical light confinement in 2-D silicon photonic crystals are theoretically compared. Light guidance, obtained by varying the refractive index in an SiO/Si/SiO[subscript 2] sandwich structure produces a bandgap for all directions and both polarizations witha gap-midgap ratio of 8.5%, and 27% for even modes only.

Large area three-dimensional (3D) photonic crystals have been fabricated either by layer-by-layer methods, colloidal self-assembly, or by macroporous silicon etching. The last mentioned method has proven to be a versatile and fast technique to manufacture simple cubic 3D photonic crystals, having a complete photonic band gap with a width of 4.99% in the infrared spectral range. This report is focused on the investigation of their homogeneity and additional numerical simulations concerning the tolerable disorder allowing still for a complete photonic band gap. Fabry-Pérot resonators, which are realized by 3D photonic crystals containing planar defects, are characterized optically in spatially resolved transmission measurements by scanning infrared Fourier spectroscopy. The impact of the observed inhomogeneities on the complete photonic band gap is studied in detail by modeling the influence of structural parameters. Fabrication tolerances for the simple cubic arrangement of intersecting air spheres in silicon are deduced. [ABSTRACT FROM AUTHOR]

A perfect two-dimensional porous alumina photonic crystal with 500 nm interpore distance was fabricated on an area of 4 cm[sup 2] via imprint methods and subsequent electrochemical anodization. By comparing measured reflectivity with theory, the refractive indices in the oxide layers were determined. The results indicate that the porous alumina structure is composed of a duplex oxide layer: an inner oxide layer consisting of pure alumina oxide of 50 nm in thickness, and an outer oxide layer of a nonuniform refractive index. We suggest that the nonuniform refractive index of the outer oxide arises from an inhomogeneous distribution of anion species concentrated in the intermediate part of the outer oxide. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A perfect two-dimensional porous alumina photonic crystal with 500 nm interpore distance is fabricated on an area of 4 cm(Super 2) via imprint methods and subsequent electrochemical anodization. The results indicate that the porous alumina structure is composed of a duplex oxide layer, an inner oxide layer consisting of pure alumina oxide of 50 nm in thickness, and an outer oxide layer of nonuniform refractive index.

We quantitatively interpret HAADF-STEM images of SrRuO3/Pr0.7Ca0.3MnO3 (SRO/PCMO) superlattices. The images were taken in a probe-corrected ( cs = 0) FEI microscope at 300 kV. The specimen thickness is estimated by comparing experimental and simulated Z-contrast ratios. The intermixing at the interfaces is different for the growth of SRO on PCMO and that of PCMO on SRO. In addition, the thermal stability of SRO/PCMO superlattices is studied by HAADF-STEM, based on a series of annealing experiments. Colored HAADF-STEM image ( V = 300 kV, cs = 0 mm) of part of a SrRuO3/Pr0.7Ca0.3MnO3 epitaxial superlattice. [ABSTRACT FROM AUTHOR]

Dense, ordered arrays of <100>-oriented Si nanorods with uniform aspect ratios up to 5:1 and a uniform diameter of 15 nm were fabricated by block copolymer lithography based on the inverse of the traditional cylindrical hole strategy and reactive ion etching. The reported approach combines control over diameter, orientation, and position of the nanorods and compatibility with complementary metal oxide semiconductor (CMOS) technology because no nonvolatile metals generating deep levels in silicon, such as gold or iron, are involved. The Si nanorod arrays exhibit the same degree of order as the block copolymer templates.