Dielectric constants of multiwall carbon nanotubes from direct current to microwave frequencies.

A cylindrical rod constructed from a uniform mixture of multiwall carbon nanotubes and alumina powders dissolved in paraffin was inserted in the center of a radio frequency cavity. The real and imaginary dielectric constants of carbon tubes at various frequencies were measured, respectively, from the resonant frequencies and the quality factors, by a resistance-inductance-cacitance (RLC) meter and a microwave network analyzer. The dielectric rod benefits the protection of the sample from adsorbing moisture and preventing the rod from filling with air, thus making accurate measurments. A tunable probe specifically designed for the field pattern of a TM010 mode is delineated to improve the microwave coupling of the dielectric microwave resonator. This refined design is expected to facilitate the measurement yielding a significant manner. The real and imaginary parts of the dielectric constant of carbon nanotubes increase and decrease, respectively as frequencies increase satisfactorily in complying with the description from the free electron Drude model.

High molecular weight polyethylene nanospheres: synthesis, physical and mechanical properties--second harmonic generation.

The weak second harmonic light generating from carbon nanotubes are detected. The signal intensity closely related to the density of pi-bonds attributed to the defects in the rolled graphene sheets, which is stimulated to have anharmonic oscillation as strongly affected by the environment. The intensities of SHG are diminished in order of well-aligned multi-wall carbon nanotubes (MWCNTs), randomly-aligned MWCNTs, and then to single-wall CNTs.

Surface modification by electric discharge implemented with electrodes composed of carbon nanotubes.

In this work the electric discharge machining (EDM) implementing with multi-wall carbon nanotubes (MWCNT) as a miniscule electrode for pursuing precise surface modification was studied. The excellent upright growth of carbon nanotubes on copper based alloy substrates by a radio frequency (RF) assisted hot filament chemical vapor deposition (HFCVD) method suggests us to exploit MWCNTs as the miniature electrodes for discharge machining. The results reveal that the electrodes are much endurable to be distorted even when the spoiling rates for the polishing of n-type Si wafer (of 10 to approximately 100 omega-cm) are up to 30 nm/min with. It is expected that MWCNTs can be applied to non-conventional material processing especially in miniature discharge machining.

Ultraviolet narrow-band rejection filters composed of multiple metal and dielectric layers.

Band rejection filters with a bandwidth as narrow as <5% that operate in the UV region can be constructed from multiple thin metal films and insulating layers. A physical model is derived to illustrate the dependence of the wavelength of maximum reflectance and rejection bandwidth on the optical constants of metal and dielectrics, on the thickness, and on the number of repetitive layers. This design prevails over conventional dielectric-dielectric coatings because of its development and simplicity in the fabricating process and its applicability to large spectral ranges.

Design criteria for band rejection filters made from multilayers of dielectric and ultrathin metal films.

Narrowband rejection filters can be constructed from multilayers of dielectric and ultrathin metal films operating in the anomalous skin effect region constrained by the optical size effect. The wavelength of the main reflecting spectrum is wholly determined by the dielectric thickness, and the bandwidth can be reduced by increasing the total number of layers and selecting the dielectric film with high refractive index while diminishing the thickness of the metal film.

Annealing effect on the optical properties of gold films deposited on silicon substrates.

The refractive indices of gold films deposited on (111) silicon wafers are measured by a polychromatic ellipsometer at various annealing temperatures below 300 degrees C. The reflectivity increases slightly during the initial 260 degrees C annealing stage and then decreases drastically by 40% near 2.06 eV as the annealing temperature rises to 293.5 degrees C. Etch pits are found on the surface as the temperature rises further.