Oxidation of Si and GaAs in air at room temperature

The oxidation of Si and GaAs single-crystals, both cleaved and etched, has been studied at room temperature in air. We found experimentally that the oxidation of GaAs follows the direct exponential law at least within a 2 years time interval. The same also holds for both cleaved and etched Si single-crystals until the oxide film reaches a thickness of about 35–40 Å: beyond this thickness the cubic law starts to dominate the oxidation rate. An interpretation of the observed experimental results is given.