1,721,084 research outputs found
Growth of epitaxial Yb silicide on Si(100) studied by metastable atom deexcitation spectroscopy and photemission
Full text linkFilms of different Yb thickness are deposited on Si(100) 2x1 and are annealed at increasing high temperature. The evolution of the valence-band electronic properties is followed with metastable deexcitation spectroscopy and photoemission. Different surface-structure phases are observed at progressively high annealing temperature. A 3x1 ordered phase is observed by low-energy electron diffraction (LEED) after annealing of the films at about 640 degreesC and it is associated to the formation of a stable silicide. Correspondingly, electronic states assigned to the Yb 6s-5d hybridized band and to Si 3s and 3p bands in the compound are observed. A further increase of the annealing temperature causes the system to evolve rapidly. At T>650 degreesC the LEED pattern shows a 3x2 periodicity. Above 700 degreesC, the films present a character similar to that of the Si substrate.Films of different Yb thickness are deposited on (formula presented) and are annealed at increasing high temperature. The evolution of the valence-band electronic properties is followed with metastable deexcitation spectroscopy and photoemission. Different surface-structure phases are observed at progressively high annealing temperature. A (formula presented) ordered phase is observed by low-energy electron diffraction (LEED) after annealing of the films at about 640 °C and it is associated to the formation of a stable silicide. Correspondingly, electronic states assigned to the Yb (formula presented) hybridized band and to Si (formula presented) and (formula presented) bands in the compound are observed. A further increase of the annealing temperature causes the system to evolve rapidly. At (formula presented) the LEED pattern shows a (formula presented) periodicity. Above 700 °C, the films present a character similar to that of the Si substrate. © 2002 The American Physical Society
Evolution of Auger peaks in GaP(110) with hydrogen chemisorption
No full textAuger spectroscopy flanked by energy loss spectroscopy was used to investigate the evolution of GaP(110) surface electronic structure upon hydrogen exposure. The paper is focussed on the modification of PL(2,3)VV Auger line shape as a function of hydrogen exposure in the exposure range between zero and Ga3d surface exciton quenching. The discussion is concentrated on the Auger emission region about 9 eV below the emission from valence band top. The line shape change can be explained on the basis of present knowledge of electronic structure of H:GaP(110) surface and ascribed to the birth of a hydrogen-induced state (H-4) at similar to 4.4 eV below valence band top. Moreover the surface stoichiometry was monitored by Auger spectroscopy through the PL(2,3)VV to GaM(2,3)M(4,5)M(4,5) peak-to-peak ratio which was found to be extremely affected at high hydrogen exposures
Revisiting the Probing Depths of Soft X-ray Absorption Techniques by Constant Initial State Photoemission Experiments
No full textWe have recently performed accurate constant initial state (CIS) Al 2p photoemission experiments on Al films covered with layers of amorphous Ge of variable thickness, using synchrotron radiation in a variable photon energy range 100–1100 eV at the BEAR beamline at Elettra. Experiments were performed within the framework of a larger research effort aimed to obtain accurate and reliable measurements of the photoelectron mean free path (MFP) at variable kinetic energy and ultimately of the probing depth of the total electron yield and total fluorescence yield (TEY, TFY) techniques. Present MFP results are compared with previous experiments and simulations, improving our present knowledge of the MFP curve in amorphous germanium and opening new experimental possibilities for accurate measurements of the probing depth. © 2021, Springer Nature Switzerland AG
Scattering mechanism of electrons interacting with surfaces in specular reflection geometry: Graphite RID G-7348-2011
No full textWe have studied the scattering mechanism of electron-energy-loss process in specular reflection geometry highlighting the presence of an elastic collision that always accompanies the inelastic one. It implies that two independent channels contribute to the inelastic cross section depending on whether the inelastic event precedes or follows the elastic one. Our results indicate that neither one of the channels is favored by propensity rules. Nevertheless, suitable experimental conditions permit to enhance contribution to the cross section of one channel with respect to the other. The possibility to single out the contribution of a given channel allows to determine without ambiguity the momentum exchanged in the inelastic collision. This is of fundamental relevance for several electron impact spectroscopies, such as electron-energy-loss spectroscopy and (e,2e), in specular reflection geometry. These results are derived from measuring the current of elastically and inelastically specularly reflected electrons as a function of the primary electron beam kinetic energy (IV curve). The incident beam energy was varied between 150 and 450 eV, the target was an highly oriented pyrolitic graphite and the range of losses investigated was 6-35 eV. A simple kinematics model that accounts for refractive effects due to the surface potential barrier, gives good agreement with the observed diffraction pattern of the elastically reflected electrons. [S0163-1829(99)01519-2]
Refinement and revalidation of the Equine Ophthalmic Pain Scale: R-EOPS a new scale for ocular pain assessment in horses
Full text linkThis study addresses the refinement and revalidation of a composite pain scale that focuses on equine facial expressions and behavioural indicators as exhibitions of ophthalmic pain. This scale included only Behavioural and Facial and Ocular expression indicators and, compared to the first version of Equine Ophthalmic Pain Scale (EOPS), item descriptors and related ratings were changed. Thirteen horses with ocular diseases that required medical or surgical treatment were enroled (group P). In each animal, the refined EOPS (R-EOPS) was applied prior to any treatment (T0) and one week later (T7). The R-EOPS was applied twice, 7 days apart, to 16 healthy control horses (group C). Two 30-second videos were recorded each time to allow the retrospective analysis by eight observers. Inter-observer reliability of items was moderate or substantial (Krippendorff's alpha, Kα>0.40) while their intra-observer reliability was substantial or almost perfect for most items (Kα ≥0.61). Both inter- and intra-observer reliability of Total Score (TS) were however excellent (Intraclass Correlation Coefficients, ICC>0.75). The TS also showed good reproducibility (Kendall coefficient=0.786, ICC=0.684) and high consistency of its items (Cronbach's α=0.847). The comparison between groups as well as the sensitivity and specificity values supported the validity of the R-EOPS. In particular, for each extra point added to the TS, the risk of the horse having pain increased by more than two times (Odds Ratio=2.079, 95%CI=1.542–2.804; P<0.001). The Receiver Operating Characteristic analysis identified 6 as the threshold value of R-EOPS for discriminating horses with ocular pathology (sensitivity=83%, specificity=100%). This scale may be an effective tool for reliably assessing the pain level in horses with ophthalmic diseases and potentially guiding pain management although it still requires large-scale application and external validation
Scattering mechanism of electrons interacting with surfaces in specular reflection geometry: Graphite
No full textWe have studied the scattering mechanism of electron-energy-loss process in specular reflection geometry highlighting the presence of an elastic collision that always accompanies the inelastic one. It implies that two independent channels contribute to the inelastic cross section depending on whether the inelastic event precedes or follows the elastic one. Our results indicate that neither one of the channels is favored by propensity rules. Nevertheless, suitable experimental conditions permit to enhance contribution to the cross section of one channel with respect to the other. The possibility to single out the contribution of a given channel allows to determine without ambiguity the momentum exchanged in the inelastic collision. This is of fundamental relevance for several electron impact spectroscopies, such as electron-energy-loss spectroscopy and (e,2e), in specular reflection geometry. These results are derived from measuring the current of elastically and inelastically specularly reflected electrons as a function of the primary electron beam kinetic energy (IV curve). The incident beam energy was varied between 150 and 450 eV, the target was an highly oriented pyrolitic graphite and the range of losses investigated was 6-35 eV. A simple kinematics model that accounts for refractive effects due to the surface potential barrier, gives good agreement with the observed diffraction pattern of the elastically reflected electrons. [S0163-1829(99)01519-2]
Refinement and revalidation of the Equine Ophthalmic Pain Scale: R-EOPS a new scale for ocular pain assessment in horses
Full text linkThis study addresses the refinement and revalidation of a composite pain scale that focuses on equine facial expressions and behavioural indicators as exhibitions of ophthalmic pain. This scale included only Behavioural and Facial and Ocular expression indicators and, compared to the first version of Equine Ophthalmic Pain Scale (EOPS), item descriptors and related ratings were changed. Thirteen horses with ocular diseases that required medical or surgical treatment were enroled (group P). In each animal, the refined EOPS (R-EOPS) was applied prior to any treatment (T0) and one week later (T7). The R-EOPS was applied twice, 7 days apart, to 16 healthy control horses (group C). Two 30-second videos were recorded each time to allow the retrospective analysis by eight observers. Inter-observer reliability of items was moderate or substantial (Krippendorff's alpha, Ka>0.40) while their intra-observer reliability was substantial or almost perfect for most items (Ka ≥0.61). Both inter- and intra-observer reliability of Total Score (TS) were however excellent (Intraclass Correlation Coefficients, ICC>0.75). The TS also showed good reproducibility (Kendall coefficient=0.786, ICC=0.684) and high consistency of its items (Cronbach's a=0.847). The comparison between groups as well as the sensitivity and specificity values supported the validity of the R-EOPS. In particular, for each extra point added to the TS, the risk of the horse having pain increased by more than two times (Odds Ratio=2.079, 95%CI=1.542-2.804; P<0.001). The Receiver Operating Characteristic analysis identified 6 as the threshold value of R-EOPS for discriminating horses with ocular pathology (sensitivity=83%, specificity=100%). This scale may be an effective tool for reliably assessing the pain level in horses with ophthalmic diseases and potentially guiding pain management although it still requires large-scale application and external validation
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