Single‐domain cobalt dot arrayswith high magnetic particle density, patterned over large areas (e.g., 10 cm diameter wafers) are fabricated by self‐assembled block copolymer lithography, using a polystyrene–poly(ferrocenyldimethylsilane) copolymer as a template. By varying the copolymer type and etching conditions the magnetic properties can be tuned. The Figure shows a typical array of Co dots with tungsten caps obtained via this procedure.

We have developed a simple, fast, and flexible technique to measure optical scattering spectra of individual metallic nanoparticles. The particles are placed in an evanescent field produced by total internal reflection of light from a halogen lamp in a glass prism. The light scattered by individual particles is collected using a conventional microscope and is spectrally analyzed by a nitrogen-cooled charge-coupled-device array coupled to a spectrometer. This technique is employed to measure the effect of particle diameter on the dephasing time of the particle plasmon resonance in gold nanoparticles. We also demonstrate the use of this technique for measurements in liquids, which is important for the potential application of particle plasmons in chemical or biological nanosensors

Three-dimensional ceramic nanostructured films were produced from silicon-containing triblock copolymer films exhibiting the double gyroid and inverse double gyroid morphologies (space group Ia3d). A one-step room-temperature oxidation process that used ozonolysis and ultraviolet irradiation effected both the selective removal of the hydrocarbon block and the conversion of the silicon-containing block to a silicon oxycarbide ceramic stable to 400 degrees C. Depending on the relative volume fraction of the hydrocarbon block to the silicon- containing block, either nanoporous or nanorelief structures were fabricated with calculated interfacial areas of approximately 40 square meters per gram and pore or strut sizes of approximately 20 nanometers.

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The behavior of poly(ferrocenyldimethylsilane) (PFS) under reactive ion etching conditions was investigated. Due to the presence of iron and silicon in the main chain, the polymer was found to be relatively stable toward oxygen plasma etching compared to common organic polymers. Depending on the conditions employed, the etching rate ratio for poly(isoprene) vs poly(ferrocenyldimethylsilane) ranged from 20:1 to 50:1. During etching, a thin iron- and silicon-containing oxide layer was formed at the surface of the organometallic polymer. The oxide layer was characterized by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) using depth profiling. Iron was found to be more resistant toward removal by oxygen plasma compared to silicon. Iron in the polymer also makes it resistive to CF4/O2 etching. A regular pattern consisting of parallel lines of PFS on a solid substrate was obtained by micromolding in capillaries (MIMIC) (a microcontact printing technique), which could be transferred into the underlying substrate. Under the conditions employed, silicon and silicon nitride substrates were etched at approximately 20 nm/min, whereas no thickness decrease was observed for the poly(ferrocenyldimethylsilane) film, even after etching times exceeding 10 min.

structure of such materials varies from spherical, interconnected pores, to a bicontinuous type arrangement of silica, to an assembly of spherical particle aggregates loosely bonded together. We are currently investigating quantitatively the evaporation kinetics of both solvents alongside the temporal changes in structure during the process of formation of these porous solids. ExperimentalMaterials: Water was passed through a reverse osmosis unit and then a Milli-Q reagent water system. Toluene (Fisher, > 99.9 %), hexane (Sigma, > 99 %) and decane (Sigma > 99 %) were passed twice through a chromatographic alumina column before use. The fumed silica powders were from Wacker-Chemie (Munich), with primary particle diameters of between 10 and 30 nm, and surface areas of 200±250 m 2 g ±1 . The silanol content of the different particles is 100 % (N20), 76 % (SLM 079) and 50 % (H30), with the coating reagent being dichlorodimethylsilane.Methods: Dispersions of hydrophilic silica-in-water, or of hydrophobic silicain-oil, were prepared by dispersing a known mass of powder into the liquid using a high intensity ultrasonic vibracell processor (Sonics & Materials) of tip diameter 0.3 cm, operating at 20 kHz and up to 10 W for 2 min. In some experiments, both hydrophilic and hydrophobic particles were dispersed simultaneously in oil initially. Emulsions were made in glass vessels by mixing the appropriate particle dispersion with the second liquid phase using a Janke & Kunkel Ultra Turrax homogenizer (rotor-stator), with a 1.8 cm head operating at 13 500 rpm for 2 min. Their type was assessed using conductivity and droptest measurements. Drop-size distributions were determined using a Malvern MasterSizer MS20 particle sizer and checked with optical microscopy (Nikon Labophot). Emulsions of different particle concentrations, oil/water volume ratios, and oil and particle hydrophobicities were prepared. They were left in air at room temperature to allow evaporation of oil and water. Such systems dry first to a gel and subsequently to the solid phase. In many cases, a tablet-like material forms that retains the shape of the container. In other cases, small angular solid fragments result. After drying to constant weight, the solid samples were mounted on aluminum studs using epoxy resin, and gently scraped with paper to expose a fresh fracture surface. This was coated with a thin (20 nm) layer of carbon and examined using a Cambridge Instruments S360 scanning electron microscope. The details of the freeze fracture field emission SEM method of liquid emulsion samples were given previously [16].

A room-temperature synthesis route for thin films of amorphous silica (a-SiO2) based on irradiation of a silicon-containing polymer by UV light in pure O2 atmosphere has been developed. The chemical conversion of spin-coated films of poly(pentamethyldisilylstyrene) (pPMDSS) to silicon oxycarbide and finally to amorphous silica is achieved by UV-assisted ozonolysis. The conversion process has been followed by Fourier transform infrared spectroscopy (FTIR), ellipsometry, and X-ray photoelectron (XPS) and Auger electron spectroscopies (AES). The control of the irradiation time allows for control of the chemical composition of the converted films ranging from that of a silicon oxycarbide for short exposure times to that of a-SiO2 after 18 h of exposure. The surface composition of the fully converted films obtained by XPS is characterized by an atomic ratio O/Si = 2.00 ± 0.07. Auger electron depth profiles reveal a uniform chemical composition of the a-SiO2 films with a residual carbon content in the bulk of the films below 1%. Converted a-SiO2 films of thicknesses up to 150 nm were achieved. Ellipsometry shows that the conversion of the films in a-SiO2 is accompanied by a progressive decrease of the film thickness and evolution of the refractive index to an asymptotic value of 1.44. The film surface of the converted films probed by optical microscopy over large areas and by atomic force microscopy (AFM) does not show any cracks and is atomically flat with a RMS roughness below 0.4 nm.