The laser induced pressure wave propagation method is often used to measure the space charge distribution in solid insulators. This method gives rise to many advantages, so it is widely used both in industrial and in research laboratories. However, it is necessary to take some precautions before treating induced signals in order to minimize calculation errors. Here, some quantitative information about the effects of approximations and the technical problems arising from this method used to study cable insulators are presented. Data from semiconductor/polyethylene samples have been obtained. Some recommendations defining an appropriate experimental protocol of space charge measurement in high voltage cable insulators are given.

Multifilamentary superconducting Nb 3 Sn wires are widely used for industrial applications. Wires processed by the Bronze Route technique are characterized by a large number of filaments Nb 1−x Sn x , with 0.18 x 0.25, corresponding to a distribution of T c between <10 and 18 K. This distribution is a critical property of the wires and is important for the optimization of the conductors. However, it is not accessible to conventional techniques, due to percolation and/or magnetic shielding effects. In order to determine the T c distribution in the sample, we have carried out specific heat measurements of various Nb 3 Sn multifilamentary wires (including the bronze matrix) in zero field and at 14 T. A deconvolution of the calorimetric data at the superconducting transition by means of a thermodynamical model was used for obtaining the distribution of T c in the whole wire volume. The measurements were extended to Nb 3 Sn wires containing Ti additions, and the results were compared. The present calorimetric method is of primary importance for the complete characterization of Nb 3 Sn wires.

Vertical processing of 0.05-µm-class SiO2 holes with an aspect ratio around 20 was realized using a dipole-ring-type magnetron reactive-ion-etching system in a mixture of C4F8/O2/Ar gas. Secondary ion mass spectrometric study of the F and C concentration profiles of the polymer deposited inside the holes in the depth direction revealed that a very small amount of polymer deposition occurred in this system. This indicates that energetic species reached the hole bottoms with excellent verticality, even in an extremely fine feature. In contrast, the CHF3/CO process (tapered shape) resulted in an extremely thick polymer and carbonized region on the sidewalls, suggesting the presence of energetic species sticking to the sidewalls. The effects of energetic species impinging onto the sidewalls and the protection resulting from polymer deposition have been discussed in terms of the etched shape and F/C depth profile. Vertical incidence of the energetic species into the holes is concluded to be a significant factor in realizing a vertical profile.

Surface structure of plasma-polymerized fluorocarbon thin film on Si and gas desorption were concurrently studied as a function of temperature between 20 and 700° C using temperature-programmed X-ray photoelectron spectroscopy with a residual gas analyzer. The films, consisting of CF3, CF2, CF and C-CF x bonds, with the F/C ratio of 1.7 were found to be stable up to 200° C and to thermally decompose above 200° C. SiF4 desorption, following gradual pyrolysis with decrease in CF3, CF2 and CF bonds due to desorption of fluorocarbon gases, was observed for F/C ratios ranging from 1 to 0.1. The pyrolytic process of the film and the thermal reaction with Si substrates were further discussed based on results of additional desorption and ion-induced reaction experiments.

Ion bombardment-induced thermal reaction between a fluorocarbon adlayer and a SiO2 surface in a reactive-ion-etching (RIE) environment which was simulated in an ultrahigh-vacuum thermal desorption mass spectroscopy (TDS) apparatus has been studied. The RIE-induced fluorocarbon chemisorbed layer, covering the SiO2 surface, was observed to be thermally stimulated to react chemically with the SiO2 in the TDS apparatus with an activation energy of approximately 1.9 eV. A terminal group, chemisorbed at the adlayer/SiO2 interface, could be an active participant in the thermal reaction. This observation indicates the possibility that chemical sputtering could occur in the actual RIE through a thermal excitation step, induced by ion bombardment. A significant difference in the RIE-induced mixing of fluorine atoms between SiO2 and Si also appeared in their TDS spectra.