Homogeneous silica formed by the oxidation of Si(100) in hyperthermal atomic oxygen

We review and summarize all of our microstructural comparisons of the silica and Si/SiOx interface created by the oxidation of Si(100) in atomic oxygen and molecular oxygen, using primarily electron microscopy techniques. A laser detonation source was used to produce atomic oxygen with kinetic energy 5.1 eV, whereas a conventional furnace was used to expose Si single crystal to thermal molecular oxygen. The silica formed on Si(100) by atomic oxygen is thicker, more homogeneous, and less amorphous (similar to alpha-quartz), as compared to the oxide layer created by molecular oxygen. High-angle annular dark field imaging and high-spatial-resolution electron energy loss spectroscopy confirmed that the Si/SiOx interface created by atomic oxygen is abrupt, containing no suboxides, as opposed to the broad interface with transitional states formed by molecular oxygen. Preliminary fluctuation electron microscopy results confirmed increased medium-range ordering in SiOx formed by atomic oxygen compared to the nonregular arrangement present in the amorphous oxide formed by the oxidation of Si(100) in molecular oxygen. Differences in the oxide films grown by exposure to atomic and molecular oxygen are discussed in the context of the thermionic emission model of silicon oxidation.