ESCA is used to characterize silicon nitride surface oxidation. Si 2p, N 1s, and O 1s binding energies and photoelectron line intensities of oxidized nitride films are compared with the corresponding lines from thick reference films of silicon, silicon nitride, silcon dioxide, and a series of oxynitrides. Rapid initial oxidation of silicon nitride surfaces occurs at room temperature on exposure of nitride films to air. A graded oxidized nitride film forms between the film surface and the nitride. Similarly, oxynitride films with gradations in composition are obtained upon oxidation of nitride films at high temperatures.

Oxide growth on etched silicon wafers at room temperature was studied as a function of etching procedure, wafer orientation, dopant concentration, and exposure to ultraviolet light. An impurity film was rapidly deposited on the silicon surface after etching with hydrofluoric acid. Impurity adsorption was distinguished from oxide growth by x-ray photoelectron spectroscopy (E'SCA). The impurity film greatly reduced the initial oxide growth rate when compared with oxide, growth on a cleaved silicon surface. The thickness of oxide films formed on etched surfaces was determined and compared using ESCA and ellipsometry.* Electrochemical Society Active Member.

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We demonstrate that the low-frequency noise in our edge junction dc superconducting quantum interference devices, with a basic 1/f flux noise of 2×10−12 Φ20/Hz at 1 Hz, can all be accounted for in terms of junction critical current fluctuations. A novel modulation readout scheme is able to cancel the effect of junction critical current fluctuations and reduce our total noise to 1×10−12 Φ20/Hz at 0.1 Hz, a level that is three times lower than the lowest flux noise ever previously reported at this frequency.

We have studied in detail the current-voltage (1-V) curves of dc SQUIDs in the presence of rf fields in the frequency range 2-18 GHz. Strong voltage locking at half-integral as well as the usual integral Shapiro step spacing is observed when the applied dc-magnetic flux is close to half-integral numbers afflux quanta. Numerical simulations are in excellent agreement with the experimental 1-V curves. The half-integral steps are found to be associated with the flipflop between two adjacent fl.uxoid states of the SQUID synchronized to the rf field.