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.

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Si-based single-electron tunneling (SET) devices have of late become an important alternative to the metal-based ones, both for ultralarge scale integration (ULSI) electronics and for electrical metrology. We have very recently been designing, fabricating, and measuring SET turnstiles, pumps, and charge-coupled devices using tunable barriers in silicon. Having shown the potential of these devices, we wish to understand the error mechanisms which may manifest themselves, and to predict the level of these errors, in order to decide how feasible these devices will be. In this paper, we devote a substantial amount of analysis to the consideration of the "dynamical" error mechanism. This particular error considers how electrons split up as the barrier is raised, or alternatively how the Coulomb blockade is formed. We then consider a wide variety of other errors, including thermal, frequency, leakage, and heating errors. We show the dependence of the error rate on each of those mechanisms, and predict maxima or minima for the corresponding parameters. In the conclusion, we discuss the various advantages Si-based turnstiles or pumps would offer with respect to the metal-based ones.

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One of the challenges that single-electron transistors (SETs) face before they can be considered technologically useful is the charge offset drift. Recently, two different types of Si SETs were shown to have a drift of only 0.01e (the fundamental charge) over several days. Those devices came from one fabrication source. Here, we present the results for Si SETs fabricated by our group (a different source) demonstrating their operation as SETs. We confirm that the charge offset drift is less than 0.01e, demonstrating the lack of charge offset drift is generic to Si devices and not dependent on the fabrication source.