The PMMA opal film was infiltrated with SiO 2 using a homemade CVD setup operating at atmospheric pressure and room temperature with SiCl 4 and H 2 O as precursors [12]. The CVD process is based on the hydrolysis of silicon tetrachloride (SiCl 4 ) on the hydrophilic surface of the spheres; these had been previously wetted with water vapor. SiCl 4 and water are both separately bubbled by a N 2 flow that sweeps the vapor phases to the reactor where the sample is placed. Controlled filling fractions can be achieved by adjusting the N 2 -flow rate and time.Patterning of the PMMA/SiO 2 composite was performed by EBL, using a Hitachi S-800 and a LEO 1455 scanning electron microscope equipped with a Raith Elphy Plus EBL control unit, at an accelerating voltage of 25 kV and exposure doses between 100 and 850 lC cm ±2 . The samples were developed for 40 s in methyl isobutyl ketone and then placed in isopropanol for 10 s to stop the developing process.The optical characterization was performed with a FTIR spectrometer, IFS 66 from Bruker with an attached IR Scope II microscope. 15 and 36 Cassegrain objectives were used to focus and collect the light from the patterned motifs. The incident and collected light cover external angles from 5 to 15 (15 objective) and 20 to 57 (36 objective) from normal incidence with respect to the (111) family of planes.HRSEM was used to observe the alterations in the opal structure. Before examination, samples had been cleaved and sputtered with a thin film of gold. Block copolymer thin films are currently of great interest as contact masks for inexpensive, large-area lithography. Films of the order of 50 nm thickness, containing a single layer of spherical or cylindrical microdomains formed by one block in a matrix of the other, have been successfully used to pattern semiconductors, [1±3] fabricate ultradense arrays of metal [4,5] and III±V semiconductor quantum dots, [6] and condense and isolate magnetic storage media. [7,8] Progress has been impeded by the lack of a versatile technique for inducing long-range order and orientation of the microdomains in a predetermined direction. For example, the striped patterns [9] formed by either cylinders or edge-on lamellaeÐwhich, if aligned, could serve as precursors to arrays of metal nanowiresÐinstead form curved, wormlike patterns with no long-range order. Techniques capable of aligning these striped patterns over areas of several lm 2 include electric fields, [10] graphoepitaxy (where the substrate is topographically prepatterned at the micrometer length scale [11,12] ), and directional crystallization of a suitable solvent. [13] Ordering over even larger areas is potentially achievable by prepatterning the substrate with the desired nanometer-scale pattern, [14,15] and then replicating this pattern in the block copolymer film; however, the aim of COMMUNICATIONS 1736

PECVD silicon nitride photonic wire waveguides have been fabricated in a CMOS pilot line. Both clad and unclad single mode wire waveguides were measured at ¼ 532, 780, and 900 nm, respectively. The dependence of loss on wire width, wavelength, and cladding is discussed in detail. Cladded multimode and singlemode waveguides show a loss well below 1 dB/cm in the 532-900 nm wavelength range. For singlemode unclad waveguides, losses G 1 dB/cm were achieved at ¼ 900 nm, whereas losses were measured in the range of 1-3 dB/cm for ¼ 780 and 532 nm, respectively.

Lithographically induced self-assembly of microstructures with a liquid-filled gap between the mask and polymer surface J.

A reflective polarizer consisting of two layers of 190 nm period metal gratings was fabricated using nanoimprint lithography. Measurements with a He–Ne laser (wavelength=632.8 nm) showed that at normal incidence, this polarizer reflects light polarized perpendicular to the grating lines (transverse magnetic polarization) with a reflectance of 54%, but strongly absorbs parallel-polarized light (transverse electric polarization) with a reflectance of only 0.25%. The enhanced polarization extinction ratio of over 200 at this wavelength is possibly related to the resonance between the two layers of metal gratings. This polarizer is thin, compact, and is suited for integrated optical systems.

In this paper we report a technique that allows a fast replication of sub-100 nm scale patterns in a thin polymer film on a substrate from a patterned mask. Using the new pattern transfer technique, we fabricated 100 nm period polymer gratings with a 50 nm linewidth above a Si substrate as an example to demonstrate its capability of producing sub-100 nm nanostructures with direct industrial applications. In our technique, a mask with protruding patterns is used to induce similar pattern formation in the molten polymer film through an electrohydrodynamic instability process. A solid positive replica of the mask is obtained by cooling the polymer below its glass transition temperature. The mask is removed afterwards for the next fabrication procedure. The polymer structures formed can be used either directly as functional devices or as etching masks for further lithography processes. The mechanism that leads to the instability and subsequent pattern formation in the polymer layer is explained. Several important physical parameters that control the whole instability process are also identified. Our theory and experiments show that the pattern transfer technique developed here is well suited for the fabrication of sub-100 nm surface patterns in thin polymer films.