Miki Egami

Pore interconnectivity of nanoclustering silica porous films as studied by positronium time-of-flight spectroscopy

Positronium time-of-flight spectroscopy with improved stability and signal-to-noise ratio, achieved by a developed off-line digital data analysis, was applied to the characterization of three types of nanoclustering silica porous films with different relative dielectric constants and refractive indices. The emission of triplet ortho-positronium (o‐Ps) from the film surface was examined as a function of incident positron energy (Ein). It was found that the o‐Ps emission peak energies from two highly porous films with similar total porosities decrease similarly to each other with increasing Ein up to 1.50keV. On the other hand, o‐Ps emission intensities from the two films differed considerably in the range between 0.5keV<Ein<4keV, which reflects a difference in pore interconnectivity between the two films with different mean secondary particle sizes. Some interconnected pores are expected to be closed by the necking at the particle contacts as calcination proceeds, possibly leading to more necks in the pore...

Film Properties of Low-Density and Ultra-Low-Dielectric-Constant Material

We studied the effect of pore diameter on the film properties of low-density porous material with special interest in the pore diameter range below 5nm. A novel low-density material, Interpenetrated SOG (IPS), was designed to realize such porous character. It is composed of a pyrolic template, which is an organic olygomer, and framework, made from SOG polymer and silica sol, forming an interpenetrated structure. Thermal decomposition of the organic component successfully resulted in films with pore diameter range below 5nm. It is found that the dielectric constant and the pore diameter depended on the density and the film strength was affected by the average pore diameter. Practically, films with the average pore size below 5nm possessed dielectric constants as low as 2.2–2.0 and sufficient strength.