Electronic Excitations in Some Transition Metals and Their Oxides. Characteristic Energy Loss Measurements up to 50 eV

Abstract

The characteristic energy losses suffered b y a 20 keV electron beam through thin films of some transition metals (Sc, Y, Zr, Hf) and of their oxides are measured using a magnetic spectrograph u p t o 50 eV. The energy loss function -1m 1/& and the complex diclectric constant are calculated. It is shown that the electron excitation spectra of metals contain two main contributions in this energy range: one due t o collective excitations of the conduction electrons, the other t o the excitation of inner p-electrons. In the case of oxides the spectra display three strong structures: there are probably two collective excitations of valence electrons followed by the excitation of inner p-electrons of the metal.Les pertes caractkristiques d'6nergie subies par u n faisceau d'6lectrons de 20 keV B la traverske de films minces de quelques m6taux de transitions placks en dkbut de s6rie (Sc, Y, Zr, Hf) e t de leurs oxydes ont 6t6 mesur6es avec un spectrographe magnetique jusqu'i 50 eV. La fonction -1m lie e t la eonstante dielectrique complexe sont calcul6es. On montre que le spectre des excitations 6lectroniques des mbtaux contient deux contributions principales dans le domaine d'6nergie considkrk : l'une due i l'excitation collective du gaz d'klectrons de conduction, l'autre B l'excitation des 6lectrons p. Dans le cas des oxydes, les spectres mettent en kvidence trois structures importantes: deux excitations collectives des 6lectrons de valence e t l'excitation des Blectrons p dn mktal.

Crystal structure and band gap determination of HfO2 thin films

“…These literature values are added to Table II. Because of the lack of experimental data in the literature for the orthorhombic HfO 2 phase, we restrict the comparison of our results to the data obtained for the monoclinic phase. In this case we find good agreement between our band gap value ͑5.3± 0.5 eV͒ and the experimental EELS band gap values determined by Yu et al 30 ͑E g = 5.25 eV͒ and by Frandon et al 29 ͑5.5± 0.2 eV͒. On the contrary, in comparison to the UV spectroscopy result ͑E g = 5.68 eV͒ of Balog et al, 31 our band gap is about 0.4 eV smaller.…”

Role of electronic excitations in the energy loss ofH2+projectiles in high-κmaterials

“…38 In the present study, up to 7 Mermin-type ELFs were necessary in order to fit the excitation spectrum for HfO 2 . 39,40 The experimental ELF for LaScO 3 was obtained from optical experiments of reflectivity 41 using a Kramers-Kronig analysis, and up to 10 Mermin-type ELFs were used in the fitting. The wake forces between fragments, which are the main responsible for the vicinage effects in the energy loss, are also implemented in the code using the dielectric formalism and the same method to account for the ELF.…”

Scanning transmission electron microscopy of gate stacks with HfO2 dielectrics and TiN electrodes

“…Low-loss energy loss features (< 30 eV) have been investigated by several authors for the chemically and structurally similar ZrO 2 [14][15][16][17][18]. Peak A corresponded to the energy of the optical band gap (~ 5.6 -5.8 eV [19,20]), whereas feature at higher energy losses (peaks E-H)…”