Effet de l'oxydation en surface et en volume sur les spectres de pertes caractéristiques d'énergie d'électrons dans les couches minces de titane

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

“…I n titanium, which was extensively studied, our spectrum exhibits a 17.3 eV plasmon peak [19], in good agreement with Wehenkel's data (17.65 eV) [ZO], but significantly different from the result (13.7 eV) given in [6]. I n a previous study of Ti thin films [21] by means of Auger spectroscopy and of 1500 eV electron energy loss measurements we have shown that the surface (but not the volume) of the samples is primarily contaminated by oxygen. The spectra presented here were .ZO examination of the results in [ Z Z ] we find that the 12 eV predominant 10;s peak cannot he associated with the bulk plasmon in titanium, as proposed in [22], but with an electronic excitation in the thin oxide layer which probably grows onto the specimen : when the surface of the Ti sample is exposed to oxygen, only the 12 and 25 eV peaks remain in the energy loss spectrum; these two values are close to those we determined for rutile TiO, [14].…”

Excitations électroniques dans TiO2 rutile et TiO mesure des pertes d'énergie des électrons entre 3 et 60 eV

“…Cette direction de q importe peu dans le cas d'échantillons optiquement isotropes (comme TiO, de symétrie cubique). Au contraire, dans les solides anisotropes (uniaxes, comme Ti02), la définition précise de l'orientation relative de q et de l'axe c est importante pour séparer les excitations de vecteur d'onde perpendiculaire ou parallèle à l'axe c. [24].…”