Electronics of the SiO2/HfO2 interface by soft X-ray photoemission spectroscopy

We presents the results of valence band studies by soft X-ray photoemission spectroscopy on ex situ prepared, ultrathin Hf-oxide layers on 0.7 nm SiO2/Si. We find that the broadening of the O2p band in the case of 0.6 nm HfO2, as compared to SiO2/Si, is due the distribution of the average O-O separation, and probably two different bond angles, Hf-O-Hf in the film, and Hf-O-Si at the interface. We determine the valence band maximum of HfO2 as 3.92 eV below the Fermi level. Valence-band offsets between SiO2 (in 0.7 nm SiO2/Si) and HfO2 (in 0.6 nm HfO2/SiO2/Si) is found to be -1.1 eV. Between HfO2 and Si, the valence- and conduction-band offset are determined as 2.94 and 1.66 eV respectively. (C) 2004 Elsevier B.V. All rights reserved.