What is the energy of the Er 4f states?
Author(s): Leandro R. Tessler, Cnthia Piamonteze, Ana Carola Iiguez, Abner de Siervo, Richard Landers, and Jonder Morais One very important problem concerning erbium-doped silicon is the electronic structure of the Er3+ impurities. In particular, it is still not clear if the 4f levels can be treated as frozen core levels or their overlap with s and p states of their neighbors must be considered explicitly. For crystalline Si, the 4f levels have been supposed to be anywhere between 20 eV below the valence band and within the energy gap. In this paper we report on the first ultraviolet photoemission spectroscopy (UPS) measurements on Er-doped a-Si:H.
