(201s) Dissolution Behavior of Thermally Grown SiO2

A critical obstacle of flexible electronics for chronic implants is the absence of thin-film barriers to biofluids with multi decade lifetimes. Recently, ultra thin layers of silicon dioxide (SiO₂), thermally grown on device-grade silicon wafers, have been shown to allow device isolation from biofluids with their abilities to be integrated onto flexible electronics. In the device platform, defect-free material perfection of the SiO₂ layer ensures zero level water permeation through the material even with tens to hundreds nanometer thicknesses. With this material property, the failure mode of the water barrier is the thinning of the layer by dissolution of SiO₂ through hydrolysis. Here, we studied dissolution behavior of the thermally grown SiO₂ with various ion types present in biofluids at near neutral solutions. The results show cation and anion specificity as well as high pH dependency, consistent with previous studies on quartz dissolution kinetics. The observation can be understood by deprotonation of Si-OH groups on the SiO₂ surface with cations and high pH, and ensuing high dissolution rates of the deprotonated site.