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, ultra-thin 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.