Chemistry and band offsets of HfO2 thin films on Si revealed by photoelectron spectroscopy and x-ray absorption spectroscopy

X-ray photoemission and X-ray absorption studies of Hf-silicate dielectric layers

“…Sayan et al [26] report a similar valence band offset to the current work, however, their conduction band offset calculation gives a value of 1.5 eV. The XAS spectra, in this study, are similar to those reported by Toyoda et al [9] for the HfO 2 layers on silicon.…”

“…This value is significantly lower than the 7.7-8.0 eV band gap determination by Punchaipetch et al [23] for nitrided HfSi x O y dielectric layers and is more in line with the values reported by Kato et al [24] which were less than 6.0 eV for silicates containing more than 50% HfO 2 . Different values have also been reported for the HfO 2 band gap with Toyoda et al [9] reporting a value of close to 5 eV while Afanas'ev et al [25] obtained a value of 5.6 eV. Since, the valence band offset measurements are relatively consistent at approximately 3.0 eV, differences in the dielectric band gap calculation leads to significant variations in the conduction band offset.…”

“…Information on the valence band offsets are extracted from the synchrotron radiation photoemission spectra acquired at 30 eV photon energy. X-ray absorption measurements at the O 1s absorption edge are used to provide information on the conduction band electronic structure as the states which contribute to the conduction band minimum (CBM) are the O 2p * mixed with the Hf 5d * and the 6s * orbitals [9,10].…”

Energy-band alignment of HfO2∕SiO2∕SiC gate dielectric stack

“…Similar behavior has also been reported in HfO 2 / IL/ Si system. 9,10 The smaller band offset of 1.5 eV corresponds to the HfO 2 / SiC band offset while the larger band offset of 2.2 eV is due to the interfacial SiO 2 / SiC band offset. It should be mentioned here that the interfacial SiO 2 / SiC band offset of 2.2 eV in HfO 2 / SiO 2 / SiC structure is smaller than the bulk SiO 2 / SiC band offset of 2.7 eV.…”

Epitaxial growth and band alignment of (GdxLa1−x)2O3 films on n-GaAs (001)

“…Energy band gaps were determined by combining photoemission and absorption in reference to E F . In XAS data, the first derivative maximum was defined as the lowest unoccupied conduction band energy (conduction band minimum, E CBM ) and the E F was determined from the binding energy of O 1s core level Park, 2005, 2004;Toyoda et al, 2004). The same value of $5.8 eV was obtained for (Gd x La 1Àx ) 2 O 3 (x = 1 and 0.97), in a different way from Al x Ga 1Àx As of which band gap depends on the composition (Graf et al, 2005).…”