Affordable Access

On the impedance of the silicon dioxide/electrolyte interface

Elsevier Sequoia
Publication Date


The small-signal impedance of electrolyte/insulator/silicon structures is partly determined by the properties of the insulator/electrolyte interface. A theoretical model for this interfacial impedance is derived. Two parallel contributions are involved: the double-layer capacitance, for which a Gouy-Chapman-Stern model is adopted, and a branch containing the capacitance related to the surface reactions with H+ and OH− ions from the electrolyte. These surface reactions cause the total interfacial impedance to be very low for insulators with a high surface reactivity such as, for instance, Al2O3 or Ta2O5. For SiO2 surfaces, the reactivity is much lower, implying a larger interfacial impedance. Measurements of the interfacial impedance were carried out at low frequencies on 12 nm SiO2 layers in NaCl electrolytes at ionic strengths of 10−4, 10−3and 10−2 M. The results agreed with the theoretical predictions which were based on parameter values obtained from independent measurements of ψ0/pH characteristics. The agreement confirms the model for the formation of the surface charge through reactions of fixed silanol groups in the SiO2 surface.

There are no comments yet on this publication. Be the first to share your thoughts.


Seen <100 times