Semiconductive dielectric SrTiO3 thin films are promising candidates for the in situ monitoring of trace levels of oxygen in semiconductor manufacturing processes. Highly sensitive oxygen sensors were prepared by atomic-layer deposition (ALD) or pulsed-laser deposition (PLD) of SrTiO3; however, there was a problem with ALD-SrTiO3 that surface defects, such as SrO surface segregation with a minor contribution from SrO2, affected the detection below an oxygen concentration [PO2/(PO2+PHe)] of 1.1×10-12, causing the reversion of ALD-SrTiO3 to a slightly high-resistance state. The coverage of the segregated surface of SrO and SrO2 on the ALD-SrTiO3 was considerably higher than that observed on the PLD-SrTiO3 surface, however, the reversion could be markedly suppressed by the additional thermal treatment, probably owing to gathering small SrO-based surface islands (building-up of bigger islands), resulting in the exposure of clean surfaces.
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