Determination of band offsets, chemical bonding, and microstructure of the $(TbxSc1−x)2O3/Si$ system

The energy band gap, the band alignment with Si, and the chemical bonding of 4–5 nm thick $(TbxSc1−x)2O3$ dielectric films were investigated as a function of composition. Films with $x=0$⁠, 0.5, and 1 were prepared by a molecular beam deposition technique on silicon substrates. The structure of the dielectric films was characterized by high resolution transmission electron microscopy. We found that upon deposition, a silicate and a silicon oxide layer were formed at the dielectric/silicon interface for all compositions. X-ray photoelectron spectroscopy was used to determine the band gap, as well as the energy band alignment with Si and the chemical structure of the films. Energy gap values of $6.0±0.2$ and $7.5±0.2eV$ were obtained for pure $Sc2O3$ and $Tb2O3$⁠, respectively, while for the mixed layer $(x=0.5)$ a value of $6.8±0.2eV$ was extracted. It was found that the valence band offset does not change with Sc addition to $Tb2O3$⁠, while the conduction band offset increases with x, from a value of $2.9±0.2eV$ for the $x=0$ (pure $Sc2O3$⁠) to a value of $5.7±0.2eV$ for $x=1$ (pure $Tb2O3$⁠).