Dear Efi,

The oxidation rate is controlled by the mass transport of the oxidizing species to the interface between the oxide layer and the underlying silicon substrate and by the surface reaction rate of the oxidizing species with silicon. At high temperature the oxidation rate is controlled by the mass transport across the oxide layer resulting in almost flat homogeneous interface. At low temperature the oxidation rate is dependent on the surface reaction rate which in turn is exponentially dependent on temperature and orientation. Therefore, the interface will no longer flat but fluctuates due to orientation dependence of the surface reaction process.

As the surface area increases and its orientation varies, the surface states also increases proportionally.There is may be other additional effects resulting from reaction mechanism of oxidizing species that may lead to the formation of active interface states.

Best wishes