Self-Limitation of Native Oxides Explained

Silicon is one of many materials whose surface will oxidize in ambient conditions. However it is one of few materials whose native oxide will self-limit its growth in a matter of hours at a thickness of similar to 2 nm. In this work, we show through the theory of repulsive van der Waals forces that this self-limitation is due, at least in part, to the interaction between the inherent material properties of a native silicon oxide film on silicon and oxidizing molecules. These molecules are not just hindered from even entering the system at all, but those that do enter the native oxide film are repelled away from the silicon - silicon oxide interface, preventing additional growth by oxidation. We also show how this repulsion is overcome by increasing ambient temperatures to subsequently increase the kinetic energy of the oxidizing molecules, calculated by the Boltzmann-Maxwell distribution, and allow oxidation to continue.