O2 can make sure the film is fully oxidized.
Too much O2 cause the tooling factor changes, film packing density decreases, refractive index decreases. The adhesion might also get worse.
Not enough O2 can't fully oxidize the film, so you can't get a reliable film if the film is exposed in air for a long time.
Too much O2 increases the chamber pressure, if your crystal is not located at the same height of the substrate, the tooling factor changes.
Too much O2 increases the voids inside the SiO2 film, let's say, you want N_SiO2=1.45, now you can get 90% SiO2, the left 10% is void, which is Air, so the final film's refractive index decreases (0.9*1.45+0.1*1=1.405).
Less O2 causes the film not fully oxidized, after a long time expose in the air, the O2 in the air may gradually oxidize the film and change the refractive index.
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发表于 2009-4-13 12:56:27
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