Crystal structures and band offsets of ultrathin HfO2–Y2O3 composite films studied by photoemission and x-ray absorption spectroscopies

Abstract

The authors have investigated ultrathin HfO2–Y2O3 composite films by photoemission spectroscopy and x-ray absorption spectroscopy (XAS) to elucidate the Y2O3 composition dependence of crystallization and band offsets. The authors have found that the crystal structure of ultrathin films can be predicted by the detailed spectral structure between 540 and 550eV in XAS. Photoemission spectroscopy and XAS reveal that the films of x=0 and 0.05 are mainly in a monoclinic phase, while those of x=0.10 and 0.20 are in a cubic phase. Regardless of the crystal structure changes by adding Y2O3 to HfO2, the band gap and band offsets remain almost unchanged.