Energy band alignments of Al2O3–HfO2/Al2O3 nanolaminates–SiO2–p-type Si structures

The energy band alignments of Al2O3–HfO2/Al2O3 nanolaminates–SiO2–p-type Si structures were constructed based on the measurement of the band parameters by reflection electron energy-loss spectroscopy and x-ray photoelectron spectroscopy. The valence band offset at HfO2/Al2O3 interface was obtained to be 0.17 ± 0.05 eV, while the valence band offset of 0.98 ± 0.05 eV was observed at HfO2/SiO2 interface. The binding energy shifts in the structures indicate that band bending occurs due to Fermi level alignment built by charge transfer across heterojunctions. From the schematic band diagrams of the structures, it is suggested that more negative charges are present on HfO2-side, which also means there are more negative charges in HfO2/Al2O3 nanolaminates, causing upward band bending in the middle part of the structures.