Excited-state spectroscopy of single Pt atoms in Si

Resonant peaks superimposed on the direct tunneling current in the low-temperature transport of Schottky barrier metal-oxide-semiconductor field-effect transistor inversion layers are investigated. The resonances are attributed to single Pt atoms that have diffused from the metallic contacts into the depletion width near the metal/semiconductor interface. Excited-state spectroscopy and magnetic fields are used to identify different levels. A double donor level in a singlet state and another level that is attributed to a triple donor state are observed.