Electric switching in sol-gel derived SiO2 films

We have investigated electrical switching behavior of sol-gel derived SiO2 films in c-Si(p)/SiO2/metal structures. The SiO2 film is fabricated from silicafilm (a soluble Si polymer in dissolved in denatured alcohol) using spin-coating technique. The thickness of the film is in the range of 300 similar to 2000 Angstrom which depends on both spinning speed and the degree of dilution. We find that, with Ag as the top contact, when the applied voltage reaches a critical value of 1.5 similar to 2.5 V, current increases rapidly many orders of magnitude higher, and an irreversible switching occurs. The switching is also found to be polarity-dependent. The switching occurs only when the top contact (Ag) is biased positively, indicating the switching involves diffusion or electromigration of Ag. Both switching voltage and current are found to scale with the top contact area of the device. The switching dynamics is studied using voltage-pulse over a duration of 300 ns to 500 ms and amplitude of 2 to 20 V. We find that the switching electrical field is strongly dependent of the delay time prior to switching, and not related to the film thickness.