The energy loss spectra and auger spectra of palladium hydride and palladium glasses
Abstract
We have measured the Auger and energy loss spectra of Pd hydrides and Pd glasses. An unusually sharp electronic transition was observed at 32.4 eV for pure Pd hydrides. The surface compositions of Pd glasses were found to be in good agreement with their bulk compositions.
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Cited by (11)
Electron energy-loss spectroscopy of the metals Pd, Cu and the ordered Cu<inf>75</inf>Pd<inf>25</inf>(1 0 0) alloy
2007, Journal of Electron Spectroscopy and Related PhenomenaElectron energy-loss spectroscopy has been employed for investigation of the electronic structure of the metals Pd, Cu and the ordered Cu75Pd25(1 0 0) alloy surfaces. Electron energy losses have been collected using primary electron beam energies ranging from 150 to 800 eV. All of the energy losses observed in these samples can be explained in terms of three types of loss mechanisms, namely, electronic transitions involving excited states, excitation of plasma oscillations and ionization of core levels. An essential deviation of the plasmon losses from the theoretical value as calculated on the basis of the free-electron gas model was found for Pd, Cu and the Cu75Pd25(1 0 0) alloy. Using analysis of the intensity of surface and bulk plasmons we can define the interval of primary electron energy Е0, where the electron beam scans only the near surface region. Experimental data are compared with optical data obtained by LMTO–ASA calculations.
Electron energy loss spectroscopic investigation of Ni metal and NiO before and after surface reduction by Ar<sup>+</sup> bombardment
2004, Journal of Electron Spectroscopy and Related PhenomenaElectron energy loss spectra (ELS) have been obtained from Ni metal, NiO and NiO after surface reduction by 2 keV Ar+ bombardment. Two predominant loss features in the ELS spectra obtained from Ni metal are assigned as the surface and bulk plasmon excitations, and numerous other features arising from single electron transitions from both the bulk and surface Ni 3d bands to higher-lying conduction bands are also present. The surface and bulk ELS features have been unambiguously identified in this study by varying the primary beam energy. The peak assignments are based on a multitude of reported data on the electronic structure of Ni and NiO obtained using several different techniques, ranging from theoretical calculations to optical measurements and previous experimental ELS data. The ELS spectra obtained from NiO are markedly different than the Ni metal spectra as expected. The fact that the NiO spectral features do not vary appreciably with primary beam energy Ep indicates that the surface electronic structure is similar to that of the bulk solid. Although most of the loss features from NiO can be attributed to interband transitions originating from the O 2p and Ni 3d states, the major peak centered at a loss energy of about 22.0 eV may be due to a collective excitation of the valence electrons. As expected, the ELS spectra obtained from the sputtered NiO surface exhibit characteristic features from both metallic Ni and NiO, with the metallic features becoming more prominent with increasing sputtering time. The most distinct change in the ELS spectra following reduction is the growth of the surface plasmon peak at 6.0 eV due to the presence of metallic Ni in the near-surface region. The loss features characteristic of bulk Ni metal are not as pronounced in the spectra obtained from the reduced NiO. These observations indicate that the metallic Ni formed during Ar+ bombardment is confined to the very near-surface region, and they also demonstrate that ELS is sensitive to differences in the properties of thin metallic films or clusters and bulk Ni metal. The present results demonstrate that ELS can be used to distinguish between metallic nickel and NiO on the sputtered NiO surface.
Electron energy loss spectroscopic investigation of palladium metal and palladium(II) oxide
2002, Journal of Electron Spectroscopy and Related PhenomenaElectron energy loss spectra (ELS) obtained from polycrystalline Pd metal and PdO powder using primary electron energies ranging from 100 to 1150 eV have been obtained and examined in an attempt to gain a better understanding of the origins of the loss features and to assess the utility of ELS in investigations of Pd catalysts. The two sets of ELS spectra differ significantly. The ELS spectra from Pd metal exhibit a predominant peak at 6.5 eV, shown to arise from a surface plasmon excitation, and two broad features at 25.1 and 31.9 eV, which originate from bulk loss processes. The broad features consist of several overlapping losses due mainly to interband transitions from the d-band, though a bulk plasmon excitation is believed to produce a feature near 24 eV. Two distinct peaks are present at 3.7 and 7.6 eV in the ELS spectra obtained from PdO, while a broad region of intensity appears over the range from 20 to 40 eV. The peak at 3.7 eV is attributed to a transition between the top of the valence band and the bottom of the conduction band. The feature at 7.6 eV is broad and arises from several overlapping features that are most likely caused by interband transitions rather than collective excitations. Furthermore, the ELS spectra obtained from PdO and oxidized Pd are also quite different indicating that ELS can provide useful information for determining the bonding states of oxygen on Pd-containing catalysts.
Characterization of palladium hydride films by electron energy loss spectroscopy and electron diffraction
1988, Acta MetallurgicaElectrolytic charging is used to hydrogenate Pd films to full stoichiometry PdH, which is checked by making use of the relation between the lattice constant of the Pd-H system and its hydrogen content. The role of the surface barrier in preventing hydrogen escape from fully charged specimens is studied with EELS technique. Electron energy loss spectra collected at different collector aperture deviation angles in a STEM are used to separate the volume loss component from the surface loss component. The results are compared with those of Pd metal and results of PdH obtained with other techniques.
On utilise le chargement électrolytique pour hydrogéner des films de palladium jusqu'à la stoechiométrie totale PdH, ce que l'on vérifie grâce à la relation qui existe entre la constante réticulaire du système Pd-H et sa concentration en hydrogène. Le rôle de la surface en tant que barrière qui empêche l'hydrogène de s'échapper des échantillons complètement chargés est étudiée par EELS. On utilise les spectres de pertes d'énergie des électrons recueillis pour différents angles de déviation du diaphragme collecteur dans un microscope électronique à balayage en transmission pour séparer les composantes deperte volumique et de perte superficielle. Les résultats sont comparés aux résultats pour le métal palladium comme aux résultats sur PdH obtenus par des techniques différentes.
Pd-Filme werden elektrolytisch bis zur zollständigen Stöchiometrie des PdH mit Waserstoff beladen; die Stöchiometrie wird über den Zusammenhang zwischen Gitterparameter und H-Gehalt nachgeprüft. Mit EELS wird die Rolle der Oberflächenbarriere untersucht, den Wasserstoff vom Austritt aus den vollständig beladenen Proben zu hindern. Mit Elektronenenergieverlust-Spektren, die unter verschiedenen Ablenkungswinkeln in einem STEM aufgenommen worden sind, werden die Verlustkomponenten im Volumen und an der Oberfläche getreent. Die Ergebnisse werden mit denen, die an reinem Pd-Metall und an PdH mit anderen Methoden erhalten wurden, verglichen.
Electron energy loss spectra of a Pd(110) clean surface
1986, Solid State CommunicationsElectron energy loss spectra of a Pd(110) clean surface have been measured at primary energies of 40–100 eV. The observed peaks are at the loss energies of ∼ 3, 4.3, 7.5, 11.5, 16, 21.3, 26.5 and 33.8 eV. The 7.5, 26.5, and 33.8 eV peaks are attributed mainly to the bulk plasmon excitations associated with 5s electrons, coupled 5s and a limited number of 4d electrons, and total (4d+5s) electrons, respectively. The rest of the peaks are ascribed mainly to one-electron excitations.
Characterisation of niobium and vanadium hydrides by electron energy loss spectroscopy and by STEM
1985, Acta MetallurgicaThe transmission electron energy loss spectra from hydrogen-containing vanadium and niobium are compared with those from the pure metals. The hydrogen induces an additional small energy loss peak at very low energies, well below that due to the plasmon loss. This peak can be interpreted as due to a band of states induced by the hydrogen several eV below the conduction bands of the metal. Because these experiments are performed in a STEM, it is possible to verify the structure of the hydride by electron microscopy and diffraction and to be certain that the energy-loss spectra come from well characterised material.
Nous comparons les spectres de pertes d'énergie des électrons par transmission dans du vanadium et du niobium contenant de l'hydrogène avec les spectres dans ces métaux purs. L'hydrogène induit un petit pic supplémentaire de perte d'énergie, nettement au-dessous du pic de perte des plasmons. On peut interpréter ce pic comme étant dû à une bande d'états induits par l'hydrogène, plusieurs eV au-dessous de la bande de conduction de ces métaux. Ces expériences étant effectuées dans un MEBT, il est possible de vérifier la structure de l'hydrure par diffraction et microscopic électroniques et de s'assurer que les spectres de pertes d'énergie proviennent de matériaux bien caractérisés.
Die Energieverlustspektren wurden in elektronenmikroskopischer Durchstrahlung an Wasserstoff-beladenen Vanadium und Niob aufgenommen und mit denen der reinen Metalle verglichen. Wasserstoff führt zu einem zusätzlichen Maximum bei sehr kleinen Energieverlusten beträchtlich unterhalb dem Plasmonmaximum. Dieses Maximum kann einem Band von Zuständen zugeschrieben werden, welches im Metall vom Wasserstoff einige eV unterhalb den Leitungsbändern hervorgerufen wird. Da diese Experimente in einem Rasterdurchstrahlungselektronenmikroskop durchgeführt wurden, konnte auβerdem die Struktur des Hydrids in Abbildung und mit Beugung bestimmt werden, d.h. die Energieverlustspektren stammen von ausführlich untersuchten Materialstellen.
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Present address: Varian Associates, Palo Alto, Calif., U.S.A.