Oxidation of room temperature silicon (001) surfaces in a hyperthermal atomic oxygen beam

This paper describes the oxidation of Si (001) surfaces at room temperature in a hyperthermal atomic oxygen beam. The laser-detonation-type atomic oxygen beam source, originally designed by Physical Sciences Inc., was used in this study. An intense 5 eV atomic oxygen beam with a fluence of 10¹⁹ atoms/cm² oxidized Si surfaces to a depth of 4.5 nm. X-ray photoelectron spectra and Fourier transform infrared spectra indicate that the amount of suboxide is large and intrinsic stress is incorporated at the silicon/oxide interface. This intrinsic stress restricts the diffusivity of atomic oxygen in the oxide film. These results suggest that a silicon dioxide overlayer for protecting materials from atomic oxygen degradation in low Earth orbit must be at least 4.5 nm thick. However, a 3.5-nm-thick film protected the underlying substrate on samples flown on the EOIM-3 flight experiment. This discrepancy can be explained by the emission of Si atoms at the Si/SiO₂ interface to the SiO₂ film under the extremely high compressive stresses.