Electronic excitations in monoclinic hafnia as studied by spatially and momentum-resolved electron energy-loss spectroscopy and ab initio density functional theory calculations

Analysis of Plasmon Loss Peaks of Oxides and Semiconductors with the Energy Loss Function

“…The loss peaks at 13.5 eV and 16 eV were interpreted as surface plasmons and volume plasmons by other DFT calculations [52]. The other features of the computed ELF near 28 eV and 33-37 eV were associated with "collective excitations" and single excitations of Hf 5d electrons, respectively, but not to true plasmons [51,52]. These computed loss peaks are close to the experimental ELF data of hω 4 = 27.7 eV, hω 5 = 35.7, and hω 6 = 38.2 eV (Table 3).…”

“…The loss peak at 13.5 eV (near the mode for hω 2 = 15.6 eV) was the only one to be assigned to a bulk valence band plasmon of mixed O 2p, Hf 5d, and 6s electrons corresponding to a zero value of Re ( (q, ω)). The loss peaks at 13.5 eV and 16 eV were interpreted as surface plasmons and volume plasmons by other DFT calculations [52]. The other features of the computed ELF near 28 eV and 33-37 eV were associated with "collective excitations" and single excitations of Hf 5d electrons, respectively, but not to true plasmons [51,52].…”

“…These computed loss peaks are close to the experimental ELF data of hω 4 = 27.7 eV, hω 5 = 35.7, and hω 6 = 38.2 eV (Table 3). The loss peak at 41 eV (near the weak peak at hω 7 = 42.5 eV) was interpreted as the total main plasmon of all electrons in HfO 2 [51], whereas the most prominent peak near 48 eV (near hω 7 = 47.3 eV) was analyzed as an Hf 5p plasmon [52]. There is also an overall agreement with the older analysis by Frandon et al for the peaks at 15.6 eV (j = 2) and 27.7 eV (j = 4) [49].…”