Metastable precursor for oxygen dissociation on Si(0 0 1) 2 × 1 resolved by high lateral resolution work function measurements

The development of contact potential difference (CPD) inhomogeneities on oxide-covered silicon samples was investigated by monitoring the CPD of a clean Si(0 0 1) 2 × 1 surface during exposure to molecular oxygen with Kelvin Probe Force Microscopy. A steady fluctuation level is reached within the completion of a monolayer of oxide. Non-continuous oxygen exposure at room temperature and at lower temperatures unequivocally demonstrates the coexistence of two oxidation processes. One of these processes involves a metastable precursor to oxygen dissociation.