In Situ Monitoring of Electrochemical Oscillations during the Transition between Dense and Porous Anodic Silica Formation

Abstract

This study investigates the mechanism responsible for the electrochemical oscillations during silicon galvanostatic anodizing. Two oscillatory regimes of anodic silica formation in dilute fluoride electrolyte are monitored by combined in-situ curvature measurement and ellipsometry. At lower applied current density, a dense silica film is formed and the oscillations features are similar to those observed in fluoride-free electrolytes. At higher applied current density, a porous silica film is formed and the oscillations progressively reappear after a transition regime without oscillations. The disappearance and the reappearance of the oscillations are associated to variations of the degree of synchronization between the self-oscillating domains. In addition, the similarities between the oscillatory regimes and the persistence of sustained oscillations during the formation of thicker silica indicate that all oscillations arise from a same mechanism that survives the oxide accumulation at the silicon surface.

Bichaoticity induced by inherent birhythmicity during the oscillatory electrodissolution of silicon

“…The frequency of the respective oscillations varies depending on the system parameters. Owing to different electrochemical fingerprints, it had origi- nally been suggested that they involve inherently different electrochemical processes 16 , though later the interpretation was favoured that they emerge from the same mechanism 17,26 . In the following we demonstrate that LA oscillations and HA oscillations indeed live on different branches, and that the transition between both states occurs through complex oscillatory behaviour.…”

Probing the oscillating Belousov-Zhabotinskii reaction with micrometer-sized electrodes: the effect of C, Pt, and Au

“…where the parameters are defined above, eq. (6)(7)(8)(9)(10)(11)(12)(13)(14). The lines in Figure 9 represent the solutions for Q = 0 (eq.15), with the regions under the curve corresponding to the oscillatory region.…”

“…Consider, for instance, life organisms periodical phenomena, seasonal changes in leaf color, heartbeat rhythm, menstrual periods, and pattern formation in biological and geological systems [9][10]. Oscillations are also associated with metal dissolution processes [11]. Because of their broadly ranging implications, there has been a renewed interest in the long-time stability [12] of these systems and the details of the diffusion layer in the micrometer scale [13].…”