A common observation in metal-based ͑specifically, those with AlO x tunnel junctions͒ single-electron tunneling ͑SET͒ devices is a time-dependent instability known as the long-term charge offset drift. This drift is not seen in Si-based devices. Our aim is to understand the difference between these, and ultimately to overcome the drift in the metal-based devices. A comprehensive set of measurements shows that ͑1͒ brief measurements over short periods of time can mask the underlying drift, ͑2͒ we have not found any reproducible technique to eliminate the drift, and ͑3͒ two-level fluctuators ͑TLFs͒ in the metal-based devices are not stable. In contrast, in the Si-based devices the charge offset drifts by less than 0.01e over many days, and the TLFs are stable. We also show charge noise measurements in a SET device over four decades of temperature. We present a model for the charge offset drift based on the observation of nonequilibrium heat evolution in glassy materials, and obtain a numerical estimate in good agreement with our charge offset drift observations. We conclude that, while the Si devices are not perfect and defect-free, the defects are stable and noninteracting; in contrast, the interacting, unstable glasslike defects in the metal-based devices are what lead to the charge offset drift. We end by suggesting some particular directions for the improvement in fabrication, and in particular, fabrication with crystalline metal-oxide barriers, that may lead to charge offset drift-free behavior.

Indium oxide (InOx) films with a thickness of 10–1100 nm were deposited onto Corning 7059 glass and silica substrates at various substrate temperatures. An unusual decrease of the lateral grain size with increasing substrate temperature during deposition was found. The changes in the conductivity of the films after exposure to ultraviolet light in vacuum and subsequent oxidation in ozone atmosphere were analyzed and related to their structural and morphological properties. It is suggested that the photoreduction and oxidation treatments affect only a thin layer less than 10 nm at the surface of the film, while the minimum bulk conductivity is mainly determined by the structural and morphological properties.

We have developed a new method for measuring the value of breakdown voltage in air for electrode separations from 400 nm to 45 m. The electrodes used were thin film Au lines evaporated on sapphire. The resulting capacitors had an area of 80ϫ 80 m 2 . We demonstrate the ability to deduce the value of the separation of the plates by the value of the capacitance. The data acquired with this method do not agree with Paschen's law for electrode separations below 10 m, as expected from previous experiments. Amongst the improvements of our method are the measurement of plate separation and the very small surface roughness ͑average of 6 nm͒.

The room temperature ozone sensing properties of polycrystalline indium oxide (InO x ) thin films have been investigated. Films with thicknesses of 10 to 1100 nm were sputtered in a dc-magnetron system onto Corning 7059 glass at various substrate temperatures and sputtering atmospheres. Initially, as-grown films were brought to a high conducting state through a photoreduction process by UV light exposure and subsequently they were exposed to a controlled ozone atmosphere. By this treatment the sensitivity of the films could be monitored. The films exhibit resistivity changes of more than five orders of magnitude. The sensitivity was studied for different ozone concentrations and at different temperatures. The response of the films increased linearly with the ozone concentration and the highest sensitivity was achieved when the measurements were carried out at room temperature. Best results were achieved with very thin InO x films (< 100 nm) deposited at room temperature in a pure oxygen atmosphere.

Dielectric permittivity of porous Si (PSi) layers formed on a low-resistivity p-type Si (0.001-0.005 .cm) is thoroughly investigated using analytical expressions within the frame of broadband transmission line characterization method in the frequency range 1-40 GHz. It is demonstrated that the value of Si resistivity is critical for the resulting PSi layer permittivity even within the above limited resistivity range. The real part of PSi dielectric permittivity changes monotonically between 1.8 and 4 by changing the Si resistivity between 0.001 and 0.005 .cm. The above study was made for porosities between 70% and 84%. The quality factor and attenuation loss of the investigated coplanar waveguide transmission lines were found to be Q = 26 and a = 0.19 dB/mm, respectively, at 40 GHz. These values are competitive to those obtained on quartz, which is one of the off-chip RF substrates with the lowest losses. This confirms the superiority of the PSi material, mentioned above, for use as a local substrate for the on-chip RF device integration.