Relating wetting and reduction processes in the Si-liquid/SiO2-solid interface

Abstract

A reactive wetting model is presented which includes a gradual reduction of a silicon dioxide substrate lowering the interface tensions and promotes spreading. The gradual reduction is described in terms of a reaction diffusion layer that extends over multiple atomic layers. The formation of silicon-suboxides generated by the reduction leads to time dependent values for the surface tensions, which in turn change the apparent contact angle Θ(t). This model describes the reactive wetting process and its instabilities, provides simple expressions for the oxygen flow, and explains anisotropic wetting patterns observed on crystalline quartz substrates. The latter is achieved by a simple coupling of wetting and an ongoing solid state reaction in the substrate that reflects the symmetry of the crystal.