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Articles de revues sur le sujet « Overlayer »

Auteur : Grafiati
Publié le 9 mars 2023
Mis à jour le 10 mars 2023

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1

SINGH, RANBER. « MAGNETIC COUPLING IN PSEUDOMORPHIC 2ML OVERLAYERS AND SANDWICH SUPERLATTICE STRUCTURES OF Cr, Mn, Fe, Co AND Ni ON FCC Cu(001) ». International Journal of Modern Physics B 24, no 04 (10 février 2010) : 405–12. http://dx.doi.org/10.1142/s0217979210055007.

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The magnetic coupling in pseudomorphic overlayer and sandwich structures of 2ML magnetic ultrathin films on Cu (001) substrate is investigated by using spin-polarized density functional theory. The 2ML magnetic overlayers have significant magnetic moment except CrNi overlayer for which magnetic moment is very small (0.004 μB/ atom ). The overlayers having one layer of Cr turn out to be antiferromagnetically coupled except CrNi/Cu overlayer which has ferromagnetic coupling. All other overlayers have ferromagnetic coupling. In contrast to ferromagnetic MnMn/Cu overlayer, the Cu/MnMn/Cu sandwich has antiferromagnetic coupling. Similar to CrFe/Cu overlayer, the Cu/CrFe/Cu sandwich has antiferromagnetic coupling, while all other sandwiches have ferromagnetic coupling. The sandwiched structures have reduced magnetic moment as compared to their overlayer counterparts. The MnMn , MnFe , and MnCo sandwiches have highly reduced magnetic moment as compared to their overlayer counterparts.
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2

Pick, Štěpán. « Tailoring the Surface Reactivity : Comparison of Pd/Nb(110) and Rh/Nb(110) ». Collection of Czechoslovak Chemical Communications 73, no 6-7 (2008) : 745–54. http://dx.doi.org/10.1135/cccc20080745.

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Ni, Pd and Pt overlayers deposited on many metallic surfaces show properties resembling those of noble metals. We pose the question whether a similar trend might occur also for other transition-metal overlayers. To this goal, we perform first-principles density-functional theory calculations for Pd(111), Rh(111) surfaces, Pd and Rh epitaxial monolayers deposited on Nb(110), and for CO chemisorption on these systems. Density functional calculations indicate that the behavior of the two overlayers is quite different. Whereas the Rh overlayer on Nb(110) resembles the Rh(111) surface, for the Pd overlayer the electronic structure around the Fermi level is strongly affected by hybridization with Nb electrons, which accounts for unique properties of the overlayer. We expect that the latter mechanism may be of importance just for Pd, Pt, Ni and not for other transition metals with lower d-electron occupation.
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3

WANG, Y. R., J. A. KUBBY et W. J. GREENE. « THIN FILM ELECTRON INTERFEROMETRY ». Modern Physics Letters B 05, no 21 (10 septembre 1991) : 1387–405. http://dx.doi.org/10.1142/s0217984991001696.

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Electron transport through thin overlayers of tin grown on a silicon substrate, and stacking-fault contrast in topographic and conductivity images of Si (111) – 7 × 7 are investigated. Resonances that depend on structural integrity of the overlayer are observed in the conductivity images, and are interpreted as consequences of electron standing-wave formation within the overlayer. The experimental spectra are analyzed using a one-dimensional model which has scattering potentials located at the sample surface and at the overlayer-substrate interface. The agreement between experiment and theory demonstrates that electron-standing wave spectra, in conjunction with bias-dependent topographic and conductivity images, are useful for probing details of buried interfaces formed by surface reconstruction and in heteroepitaxial growth.
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4

Cordill, M. J., N. R. Moody et D. F. Bahr. « Quantifying improvements in adhesion of platinum films on brittle substrates ». Journal of Materials Research 19, no 6 (juin 2004) : 1818–25. http://dx.doi.org/10.1557/jmr.2004.0232.

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This study used nanoindentation coupled with stressed overlayers to evaluate the effect of titanium interlayers on the interfacial fracture energy of platinum films on SiO2 substrates. Interfacial fracture energy was calculated three ways: from platinum buckles that formed spontaneously upon deposition of the film, from buckles that formed upon deposition of a stressed tungsten overlayer, and from blisters triggered by indentation of a platinum film with a tungsten stressed overlayer. The calculated values for the interfacial fracture energy of the Pt-SiO2 interface were 0.2 and 0.5 J/m2 for indentation blisters and spontaneous buckles, respectively. The effect of a titanium interlayer on adhesion was examined using a tungsten stressed overlayer coupled with nanoindentation. The addition of a titanium layer improved the adhesion of the platinum film on SiO2 from 0.2 to 1.0 J/m2.
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5

Song, Jaewon, Hye Ryeong Kim, Jaehoo Park, Seehwa Jeong et Cheol Seong Hwang. « Oxidation Behavior of TiAlN Barrier Layers with and without Thin Metal Overlayers for Memory Capacitor Applications ». Journal of Materials Research 17, no 7 (juillet 2002) : 1789–94. http://dx.doi.org/10.1557/jmr.2002.0265.

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The oxidation behavior of sputtered TiAlN thin-film barrier layers was studied by cross-section transmission electron microscopy. Bare 100-nm-thick TiAlN films on SiO2/Si began to oxidize from the surface after annealing in air for 10 min from about 550 °C. Annealing at 700 °C oxidized half of the layer thickness. A 100-nm-thick Pt overlayer on the barrier layer retarded macroscopic oxidation at 650 °C. However, a 10-nm-thick Pt overlayer accelerated oxidation as a result of the catalytic dissociation of O2 molecules to form O atoms, which oxidized the barrier layer at 550 °C to the same extent as without the thin Pt overlayer at 650 °C. The effects of other thin metal overlayers, such as Ru and Ir, were also investigated. Ru and Ir did not accelerate TiAlN oxidation due to the absence of catalytic activity.
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6

Lindgren, S. Å., et L. Walldén. « Overlayer states ». Surface Science 211-212 (avril 1989) : 394–403. http://dx.doi.org/10.1016/0039-6028(89)90795-4.

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Lindgren, S. Å., et L. Walldén. « Overlayer states ». Surface Science Letters 211-212 (avril 1989) : A124. http://dx.doi.org/10.1016/0167-2584(89)90343-5.

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8

Kerdja, T., F. Dahmani et D. Ghobrini. « Simple evidence of radiation transport in coated plastic targets ». Laser and Particle Beams 9, no 2 (juin 1991) : 563–68. http://dx.doi.org/10.1017/s0263034600003578.

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Planar coated targets of Aluminum and Gold overlayers were irradiated with 1.06-μm laser light at intensities 1011–5 × 1013 W/cm2. The energy penetration depth, the ablated plasma, and the X-ray emission were characterized. Results show significant energy transport through the overlayer.
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9

DE COSS, R. « ELECTRONIC STRUCTURE OF STRAINED VANADIUM OVERLAYERS ON W(100) AND Ta(100) ». Surface Review and Letters 03, no 04 (août 1996) : 1505–9. http://dx.doi.org/10.1142/s0218625x96002503.

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We study the role of hybridization and overlayer–substrate lattice mismatch in determining the surface electronic structure of strained V monolayers and bilayers on W(100) and Ta(100). The local density of states is calculated in the tight-binding approximation within the surface-Green-function-matching formalism. For one monolayer of V on W(100) and Ta(100), the strong monolayer–substrate 3d–5d hybridization determines the features of the surface local density of states, with essentially no differences between 1V/W(100) and 1V/Ta(100). For the bilayer we find that the electronic structure of the topmost layer depends strongly on the lattice mismatch between overlayer and substrate. In particular, we find that the surface local density of states at the Fermi level in 2V/Ta(100) is 69% higher than in 1V/Ta(100); the lattice mismatch between bulk constants of V and Ta is 9.0%. These results indicate that strain induces strong band narrowing in vanadium overlayers on transition metals, despite the large overlayer–substrate hybridization, but depends critically on the film thickness.
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10

Li, Haobo, Jianping Xiao, Qiang Fu et Xinhe Bao. « Confined catalysis under two-dimensional materials ». Proceedings of the National Academy of Sciences 114, no 23 (22 mai 2017) : 5930–34. http://dx.doi.org/10.1073/pnas.1701280114.

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Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface. A similar result has been found on Pt(110) and Pt(100) surfaces covered with graphene. The microenvironment created by coating a catalyst surface with 2D material overlayer can be used to modulate surface reactivity, which has been illustrated by optimizing oxygen reduction reaction activity on Pt(111) covered by various 2D materials. We demonstrate a concept of confined catalysis under 2D cover based on a weak van der Waals interaction between 2D material overlayers and underlying catalyst surfaces.
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11

Davidson, Alisha L., Paul B. Webb, Stewart F. Parker et David Lennon. « An Inelastic Neutron Scattering Investigation of the Temporal Behaviour of the Hydrocarbonaceous Overlayer of a Prototype Fischer-Tropsch to Olefins Catalyst ». Topics in Catalysis 64, no 9-12 (17 mars 2021) : 631–37. http://dx.doi.org/10.1007/s11244-021-01419-y.

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AbstractA dual sodium and sulfur promoted haematite, representative of a candidate Fischer-Tropsch to olefins (FTO) catalyst, is prepared and contrasted with the performance of an unpromoted hematite sample in the ambient pressure CO hydrogenation reaction at 623 K as a function of time-on-stream (0–24 h). In-situ post-reaction temperature-programmed oxidation measurements show the carbon evolutionary phase of the catalyst conditioning process to be retarded for the FTO catalyst. Ex-situ inelastic neutron scattering measurements show the promoters perturb the formation of a previously described hydrocarbonaceous overlayer. Specifically, whilst the sp3 hybridised C–H modes of the hydrocarbonaceous overlayer are almost unaffected by the additives, the formation of the overlayer’s sp2 hybridised C–H modes are noticeably impeded. The results are discussed in terms of the Na/S promoters disturbing the formation of an ordered hydrocarbonaceous overlayer that is thought to constrain the supply of adsorbed hydrogen atoms, which favours the formation of unsaturated hydrocarbons associated with the FTO process.
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12

Chai, Herzl, et Brian Lawn. « Role of Adhesive Interlayer in Transverse Fracture of Brittle Layer Structures ». Journal of Materials Research 15, no 4 (avril 2000) : 1017–24. http://dx.doi.org/10.1557/jmr.2000.0145.

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The role of a soft adhesive interlayer in determining critical conditions for fracture in brittle layer structures from indentation with hard spheres is investigated. A model transparent trilayer system consisting of a glass plate overlayer (thickness range 80 μm to 2 mm) joined to a glass plate underlayer (thickness 5.6 mm) by an epoxy adhesive (thickness range 5 μm to 8 mm), loaded at its top surface with a hard tungsten carbide sphere (radius 3.96 mm), facilitatesin situobservations of the crack initiation and propagation. Whereas in bulk glass fracture occurs by inner Hertzian cone cracking immediately outside the contact circle, the soft adhesive allows the overlayer glass plate to flex, initiating additional transverse fracture modes within the overlayer: downward-extending outer ring cracks at the top glass surface well outside the contact, and upward-extending radial cracks at the bottom glass surface (i.e., at the glass/adhesive interface) on median planes containing the contact axis. The top and bottom surfaces of the glass overlayers are given selective prebonding abrasion treatments to ensure uniform flaw states, so as to enable accurate comparisons between crack initiation conditions. The adhesive bonding is strong enough to preclude delamination in our layer system. Of the three transverse crack systems, the subsurface radials generates most easily in systems with large adhesive thicknesses (and smaller overlayer thicknesses). Semi-empirical relations are specified for the dependence of the critical loads for radial and ring cracking on adhesive as well as overlayer thickness, based on the assumption that crack initiation occurs when the maximum tensile stresses in the flexing glass plate exceed the bulk strength of the (abraded) glass. Coupled with the traditional “Auerbach's law” for cone crack initiation, these relations afford a basis for the construction of simple design diagrams for brittle layer systems joined by adhesives.
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13

Dias, Luís P., Filipe C. Correia, Joana M. Ribeiro et Carlos J. Tavares. « Photocatalytic Bi2O3/TiO2:N Thin Films with Enhanced Surface Area and Visible Light Activity ». Coatings 10, no 5 (1 mai 2020) : 445. http://dx.doi.org/10.3390/coatings10050445.

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Bi2O3 nanocone films functionalized with an overlayer of TiO2 were deposited by d.c. reactive magnetron sputtering. The aforementioned nanocone structures were formed via a vapour-liquid-solid (VLS) growth, starting from a catalytic bismuth seed layer. The resultant nanocones exhibit an improved surface area, measured by atomic force microscopy, when compared to non-VLS deposition of the same metal oxide. X-ray diffraction texture analysis enabled the determination of the crystallographic β-phase of Bi2O3. A very thin TiO2 overlayer (6 nm thick), undoped and doped with nitrogen, was deposited onto the nanocones template, in order to functionalize these structures with a photocatalytic, self-cleaning, cap material. N-doped TiO2 overlayers increased the selective absorption of visible light due to nitrogen doping in the anatase cell, thus, resulting in a concomitant increase in the overall photocatalytic efficiency.
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14

McKenzie, M. T., et J. L. Koenig. « Further Developments in the Methodology of Surface Analysis by FT-IR : Quantitative Aspects of Diffuse Reflectance Methods ». Applied Spectroscopy 39, no 3 (mai 1985) : 408–12. http://dx.doi.org/10.1366/0003702854248755.

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The quantitative aspects of diffuse reflectance FT-IR are explored for standard E-glass/AAPS ( N-2-aminoethyl-3-aminopropyltrimethoxysilane) treated samples. Nondestructive sample preparation procedures are used. One generates calibration curves by plotting the normalized integrated intensity of the coupling agent bands in the 2990–2800 and 1700–1500 cm−1 regions vs. the concentration of the treatment solution. The data are derived by DRIFT spectroscopy, and the above results are plotted for the overlayer technique as well as for no overlayer. The scatter in the quantitative data due to fiber orientation effects has been measured and is found to be significant (20–30%). However, averaging over several orientations of the fibers results in a linear dependence of the integrated intensities of the coupling agent bands on solution concentration. The well-known breakpoint that has been observed for other coupling agent systems does not appear in the curve derived from the averaged spectra. The above-mentioned scatter is eliminated by the use of KBr overlayers on the samples. Linear calibration curves relating band intensity to concentration can be constructed. When the overlayer procedure is used, breakpoints do occur in the calibration curves. The position of these breakpoints agrees well with observations for the similar coupling agent γ-APS.
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15

MANNSFELD, STEFAN C. B., et TORSTEN FRITZ. « ADVANCED MODELLING OF EPITAXIAL ORDERING OF ORGANIC LAYERS ON CRYSTALLINE SURFACES ». Modern Physics Letters B 20, no 11 (10 mai 2006) : 585–605. http://dx.doi.org/10.1142/s0217984906011189.

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A fine balance between weak molecule-molecule interactions and usually only weakly laterally varying molecule-substrate interactions governs the physical structure of organic-inorganic and organic-organic heteroepitaxial thin films. Therefore, it is important to investigate the energetics of realistically large overlayer domains. So far, Potential calculations for large domains of organic overlayers on crystalline substrates were computationally demanding due to the vast number of atoms to be considered. Here, we present a technique which for the first time enables the calculation of both the molecule-substrate interaction potential and the molecule-molecule interaction potential for large molecular domains (up to several thousands of rather large molecules) by utilizing potential energy grid files. This technique does not only allow the investigation of the substrate influence but also full Monte-Carlo based structural optimizations, if applied to 2D crystalline overlayers. Furthermore, it provides an estimate for the energetic gain combined with the differently aligned overlayer domains. In several examples we will discuss the usefulness of this method. As a general result, we will provide evidence that energetically favorable lattice structures in OMBE systems are not restricted to commensurate unit cells or coincident super cells.
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16

Okuhara, T., et J. M. White. « Selective electron-induced decomposition of CVD SiO2 overlayers on oxides ». Journal of Materials Research 2, no 5 (octobre 1987) : 610–13. http://dx.doi.org/10.1557/jmr.1987.0610.

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The electron-induced decomposition (EID) of SiO2 overlayers on various high surface area oxide substrates was studied using Auger electron analysis (AES). Bulk SiO2 was stable upon electron bombardment, but bulk Al2O3 decomposed readily to elemental Al when the primary electron beam energy was 2 keV and the beam current was 6–16 μA. On the other hand, SiO2 overlayers having an average thickness of about 10 Å on Al2O3 decomposed selectively under the same conditions. In contrast to Al2O3 substrates, SiO2 overlayers on TiO2, ZrO2, and MgO were quite stable to the same electron bombardment. Therefore it is concluded that Al2O3 accelerates the EID of SiO2 overlayers and the SiO2 overlayer suppresses EID of Al2O3 substrates.
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17

ANDERSEN, JESPER N. « HIGH-RESOLUTION CORE-LEVEL PHOTOEMISSION INVESTIGATIONS OF ALKALI ON ALUMINUM ADSORPTION SYSTEMS ». Surface Review and Letters 02, no 03 (juin 1995) : 345–57. http://dx.doi.org/10.1142/s0218625x95000340.

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The use of high-resolution core-level photoemission spectroscopy for investigating the geometrical aspects of alkali adsorption on aluminum surfaces is reviewed. Examples are given of the use of the technique for studies of the submonolayer growth modes of alkali overlayers, of the geometry of the strongly reconstructed ordered overlayer structures, and of temperature-induced phase transformations between metastable and stable alkali-induced structures.
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18

Lee, Hak Hyeon, Dong Su Kim, Ji Hoon Choi, Young Been Kim, Sung Hyeon Jung, Swagotom Sarker, Nishad G. Deshpande, Hee Won Suh et Hyung Koun Cho. « Optimal n-Type Al-Doped ZnO Overlayers for Charge Transport Enhancement in p-Type Cu2O Photocathodes ». Micromachines 12, no 3 (22 mars 2021) : 338. http://dx.doi.org/10.3390/mi12030338.

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An effective strategy for improving the charge transport efficiency of p-type Cu2O photocathodes is the use of counter n-type semiconductors with a proper band alignment, preferably using Al-doped ZnO (AZO). Atomic layer deposition (ALD)-prepared AZO films show an increase in the built-in potential at the Cu2O/AZO interface as well as an excellent conformal coating with a thin thickness on irregular Cu2O. Considering the thin thickness of the AZO overlayers, it is expected that the composition of the Al and the layer stacking sequence in the ALD process will significantly influence the charge transport behavior and the photoelectrochemical (PEC) performance. We designed various stacking orders of AZO overlayers where the stacking layers consisted of Al2O3 (or Al) and ZnO using the atomically controlled ALD process. Al doping in ZnO results in a wide bandgap and does not degrade the absorption efficiency of Cu2O. The best PEC performance was obtained for the sample with an AZO overlayer containing conductive Al layers in the bottom and top regions. The Cu2O/AZO/TiO2/Pt photoelectrode with this overlayer exhibits an open circuit potential of 0.63 V and maintains a high cathodic photocurrent value of approximately −3.2 mA cm−2 at 0 VRHE for over 100 min.
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19

Wang, Zumin, Lars P. H. Jeurgens, Jiang Y. Wang, Fritz Phillipp et E. J. Mittemeijer. « High-resolution transmission-electron-microscopy study of ultrathin Al-induced crystallization of amorphous Si ». Journal of Materials Research 24, no 11 (novembre 2009) : 3294–99. http://dx.doi.org/10.1557/jmr.2009.0404.

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The process of ultrathin Al-induced crystallization of amorphous Si (a-Si) has been investigated by using high-resolution transmission electron microscopy and Auger electron spectroscopic depth profiling. Ultrathin Al overlayers, with thicknesses of 2.0 and 4.5 nm, have been shown to be capable of inducing full crystallization of an a-Si bottom layer as thick as 40 nm at temperatures as low as 320 °C. After full crystallization of a-Si, the Al of the original 2.0-nm Al overlayer completely moved through the Si layer, leaving a high-purity, large-grained crystalline Si layer above it. Such movement of Al also occurs for the originally 4.5-nm Al overlayer, but in this case the crystallized Si layer is relatively fine-grained and contains ∼5.0 at.% of residual Al nanocrystals distributed throughout the layer. The observations have been interpreted on the basis of sites available for nucleation of crystalline Si in the microstructure of the Al/Si layer system upon annealing.
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Capdevila-Cortada, Marçal. « The overlayer trade-off ». Nature Catalysis 4, no 4 (avril 2021) : 261. http://dx.doi.org/10.1038/s41929-021-00614-0.

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21

Zalm, P. C. « Overlayer corrections in XPS ». Surface and Interface Analysis 26, no 5 (1 mai 1998) : 352–58. http://dx.doi.org/10.1002/(sici)1096-9918(19980501)26:5<352 ::aid-sia378>3.0.co;2-l.

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22

Martinez, Miranda, et Anil R. Chourasia. « Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy ». Nanomaterials 12, no 2 (8 janvier 2022) : 202. http://dx.doi.org/10.3390/nano12020202.

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The Ti/SnO2 interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO2 substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO2 and the titanium overlayer at the interface. The SnO2 was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO2 to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO2, elemental titanium, TiO2, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO2 upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.
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Davis, G. D. « Overlayer interactions with (HgCd)Te ». Journal of Vacuum Science & ; Technology A : Vacuum, Surfaces, and Films 6, no 3 (mai 1988) : 1939–45. http://dx.doi.org/10.1116/1.575210.

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Lu, Wen-Chang, Tao Zhang et Kai-Ming Zhang. « Impurity Effects on Overlayer Structures ». Communications in Theoretical Physics 18, no 4 (décembre 1992) : 395–98. http://dx.doi.org/10.1088/0253-6102/18/4/395.

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25

Aytug, T., A. Goyal, N. Rutter, M. Paranthaman, J. R. Thompson, H. Y. Zhai et D. K. Christen. « High critical current density YBa2Cu3O7–δ coatings on LaMnO3-buffered biaxially textured Cu tapes for coated conductor applications ». Journal of Materials Research 18, no 4 (avril 2003) : 872–77. http://dx.doi.org/10.1557/jmr.2003.0120.

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High critical current density (high-Jc) YBa2Cu3O7–δ (YBCO) films were obtained by pulsed laser ablation on biaxially textured Cu substrates. To achieve epitaxy of LaMnO3 (LMO) on Cu, thin epitaxial Ni overlayers were deposited on Cu tapes. The structure comprises the layer sequence of YBCO/LMO/Ni/Cu. For 200-nm-thick YBCO, self-field Jc values exceeding 1 × 106 A/cm2 at 77 K were achieved. Characterization of these short prototype conductors revealed good structural and morphological properties. Magnetic analysis suggested that hysteretic loss due to the ferromagnetic Ni overlayer is minimal.
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Griffiths, Lee, et Les Bradley. « Calculation of Carbonaceous Overlayer Thickness in XPS to Yield Substrate Stoichiometries ». Applied Spectroscopy 46, no 9 (septembre 1992) : 1426–30. http://dx.doi.org/10.1366/0003702924123809.

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A method has been developed which calculates the thickness of the hydrocarbon overlayer from x-ray photoemission spectroscopy (XPS) spectra. The method is specific to each sample and utilizes the relative intensity of the C 1 s peak and all other peaks. Attenuations calculated with this overlayer thickness yield more accurate substrate stoichiometries. A rough-sample model is also developed which not only explains previous anomalies in the thickness of hydrocarbon overlayer calculated but is capable of yielding further accuracy in substrate stoichiometries.
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Sudagar, Alcina Johnson, Neha Venkatesh Rangam, Artur Ruszczak, Paweł Borowicz, József Tóth, László Kövér, Dorota Michałowska, Marek Ł. Roszko, Krzysztof R. Noworyta et Beata Lesiak. « Valorization of Brewery Wastes for the Synthesis of Silver Nanocomposites Containing Orthophosphate ». Nanomaterials 11, no 10 (10 octobre 2021) : 2659. http://dx.doi.org/10.3390/nano11102659.

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Brewery wastes from stage 5 (Wort precipitate: BW5) and stage 7 (Brewer’s spent yeast: BW7) were valorized for the synthesis of silver phosphate nanocomposites. Nanoparticles were synthesized by converting silver salt in the presence of brewery wastes at different temperatures (25, 50, and 80 °C) and times (10, 30, and 120 min). Unexpectedly, BW7 yielded Ag3PO4 nanoparticles with minor contents of AgCl and Ag metal (Agmet). Contrastingly, BW5 produced AgCl nanoparticles with minor amounts of Ag3PO4 and Agmet. Nanocomposites with different component ratios were obtained by simply varying the synthesis temperature and time. The morphology of the nanocomposites contained ball-like structures representative of Ag3PO4 and stacked layers and fused particles representing AgCl and Agmet. The capping on the nanoparticles contained organic groups from the brewery by-products, and the surface overlayer had a rich chemical composition. The organic overlayers on BW7 nanocomposites were thinner than those on BW5 nanocomposites. Notably, the nanocomposites exhibited high antibacterial activity against Escherichia coli ATCC 25922. The antibacterial activity was higher for BW7 nanocomposites due to a larger silver phosphate content in the composition and a thin organic overlayer. The growth of Agmet in the structure adversely affected the antimicrobial property of the nanocomposites.
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Secchi, Valeria, Stefano Franchi, Monica Dettin, Annj Zamuner, Klára Beranová, Alina Vladescu, Chiara Battocchio, Valerio Graziani, Luca Tortora et Giovanna Iucci. « Hydroxyapatite Surfaces Functionalized with a Self-Assembling Peptide : XPS, RAIRS and NEXAFS Study ». Nanomaterials 10, no 6 (12 juin 2020) : 1151. http://dx.doi.org/10.3390/nano10061151.

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Hydroxyapatite (HAP) coatings can improve the biocompatibility and bioactivity of titanium alloys, such as Ti6Al4V, commonly used as material for orthopedic prostheses. In this framework, we have studied the surface of HAP coatings enriched with Mg and either Si or Ti deposited by RF magnetron sputtering on Ti6Al4V. HAP coatings have been furtherly functionalized by adsorption of a self-assembling peptide (SAP) on the HAP surface, with the aim of increasing the material bioactivity. The selected SAP (peptide sequence AbuEAbuEAbuKAbuKAbuEAbuEAbuKAbuK) is a self-complementary oligopeptide able to generate extended ordered structures by self-assembling in watery solutions. Samples were prepared by incubation of the HAP coatings in SAP solutions and subsequently analyzed by X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopies, in order to determine the amount of adsorbed peptide, the peptide stability and the structure of the peptide overlayer on the HAP coatings as a function of the HAP substrate and of the pH of the mother SAP solution. Experimental data yielded evidence of SAP adsorption on the HAP surface, and peptide overlayers showed ordered structure and molecular orientation. The thickness of the SAP overlayer depends on the composition of the HAP coating.
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Jenkins, S. J., et G. P. Srivastava. « Atomic Structure of a Monolayer of Ge on Si(001)(2 × 1) ». Surface Review and Letters 05, no 01 (février 1998) : 97–100. http://dx.doi.org/10.1142/s0218625x98000207.

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We present results of first-principles pseudopotential calculations for an ordered monolayer growth of Ge on Si(001)(2 × 1). Our results strongly support the asymmetric Ge–Ge dimer model. We also provide a detailed discussion on the nature of the bonding within the overlayer and between the overlayer and the substrate.
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30

Whitman, L. J., Joseph A. Stroscio, R. A. Dragoset et R. J. Celotta. « Insulating Cs overlayer on InSb(110) ». Physical Review B 44, no 11 (15 septembre 1991) : 5951–54. http://dx.doi.org/10.1103/physrevb.44.5951.

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Richter, Roy, J. G. Gay et John R. Smith. « Spin Separation in a Metal Overlayer ». Physical Review Letters 54, no 25 (24 juin 1985) : 2704–7. http://dx.doi.org/10.1103/physrevlett.54.2704.

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Pimbley, J. M., T. ‐M Lu et G. ‐C Wang. « Island coalescence in a chemisorbed overlayer ». Journal of Vacuum Science & ; Technology A : Vacuum, Surfaces, and Films 4, no 3 (mai 1986) : 1357–61. http://dx.doi.org/10.1116/1.573570.

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Kwei, C. M., S. Y. Chiou et Y. C. Li. « Electron inelastic interactions with overlayer systems ». Journal of Applied Physics 85, no 12 (15 juin 1999) : 8247–54. http://dx.doi.org/10.1063/1.370666.

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34

Mueller, D., T. N. Rhodin et P. A. Dowben. « Halogen Overlayer Structures on Fe(110) ». Berichte der Bunsengesellschaft für physikalische Chemie 90, no 3 (mars 1986) : 281–84. http://dx.doi.org/10.1002/bbpc.19860900325.

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Yao, M. H., David J. Smith et I. E. Wachs. « TEM study of supported catalyst clusters ». Proceedings, annual meeting, Electron Microscopy Society of America 49 (août 1991) : 1030–31. http://dx.doi.org/10.1017/s0424820100089469.

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In the present work we have studied two-dimensional metal oxide overlayers (Re2O7, WO3, etc) deposited on a second high-surface-area metal oxide substrate (TiO2, Al2O3, etc). The molecular structure of these surface metal oxide species has been extensively studied in the past decade by Raman spectroscopy and EXAFS because of their importance in catalytic applications. However, direct observations of these overlayers are still needed in order to better understand the basic properties of the overlayer species. High resolution electron microscopy(HREM) is one of the most commonly used methods for direct characterization of small catalyst particles. It can provide particle size distributions and information about particle disposition over the support materials. But it is generally believed that bright field imaging is only well suited for particles sizes larger than about 10 Å. For smaller metal particles on typical supports, HAADF in STEM has been proposed as a better choice.
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36

Alibabaei, Leila, Benjamin D. Sherman, Michael R. Norris, M. Kyle Brennaman et Thomas J. Meyer. « Visible photoelectrochemical water splitting into H2 and O2 in a dye-sensitized photoelectrosynthesis cell ». Proceedings of the National Academy of Sciences 112, no 19 (27 avril 2015) : 5899–902. http://dx.doi.org/10.1073/pnas.1506111112.

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A hybrid strategy for solar water splitting is exploited here based on a dye-sensitized photoelectrosynthesis cell (DSPEC) with a mesoporous SnO2/TiO2 core/shell nanostructured electrode derivatized with a surface-bound Ru(II) polypyridyl-based chromophore–catalyst assembly. The assembly, [(4,4’-(PO3H2)2bpy)2Ru(4-Mebpy-4’-bimpy)Ru(tpy)(OH2)]4+ ([RuaII-RubII-OH2]4+, combines both a light absorber and a water oxidation catalyst in a single molecule. It was attached to the TiO2 shell by phosphonate-surface oxide binding. The oxide-bound assembly was further stabilized on the surface by atomic layer deposition (ALD) of either Al2O3 or TiO2 overlayers. Illumination of the resulting fluorine-doped tin oxide (FTO)|SnO2/TiO2|-[RuaII-RubII-OH2]4+(Al2O3 or TiO2) photoanodes in photoelectrochemical cells with a Pt cathode and a small applied bias resulted in visible-light water splitting as shown by direct measurements of both evolved H2 and O2. The performance of the resulting DSPECs varies with shell thickness and the nature and extent of the oxide overlayer. Use of the SnO2/TiO2 core/shell compared with nanoITO/TiO2 with the same assembly results in photocurrent enhancements of ∼5. Systematic variations in shell thickness and ALD overlayer lead to photocurrent densities as high as 1.97 mA/cm2 with 445-nm, ∼90-mW/cm2 illumination in a phosphate buffer at pH 7.
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Koin, P. J., A. Kilislioglu, M. Zhou, J. L. Drummond et L. Hanley. « Analysis of the Degradation of a Model Dental Composite ». Journal of Dental Research 87, no 7 (juillet 2008) : 661–65. http://dx.doi.org/10.1177/154405910808700712.

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Dental composites undergo material property changes during exposure to the oral environment and may release compounds of potential toxicity, such as bisphenol A. Degradation of dental composites was studied in a simplified overlayer model in which bisphenol A diglycidyl methacrylate (BisGMA) was covalently bound to a porous silicon oxide surface. It was hypothesized that the chemical structure of this overlayer would allow release of bisphenol A, BisGMA, and the decomposition products thereof, upon exposure to water for an extended period. Liquid chromatography mass spectrometry found leaching of intact BisGMA and several degradation products that contained the bisphenol A moiety from the overlayer into distilled water after 2 wks of aging. The absence of bisphenol A release from the overlayer reduces concerns regarding its potential health risk in dental composites. Nevertheless, health concerns might arise with respect to BisGMA and the leached degradation products, since they all contain the bisphenol A moiety. Abbreviations: BisGMA, bisphenol A diglycidyl methacrylate; HPLC, high-performance liquid chromatography; LCMS, liquid chromatography mass spectrometry; MA, methacrylic acid; MPS, 3-(trimethoxysilyl) propyl methacrylate; m/z, mass-to-charge ratio; and TIC, total ion chromatogram.
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38

Chourasia, A. R., J. L. Hickman, R. L. Miller, G. A. Nixon et M. A. Seabolt. « X-Ray Photoemission Study of the Oxidation of Hafnium ». International Journal of Spectroscopy 2009 (25 décembre 2009) : 1–6. http://dx.doi.org/10.1155/2009/439065.

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About 20 Å of hafnium were deposited on silicon substrates using the electron beam evaporation technique. Two types of samples were investigated. In one type, the substrate was kept at the ambient temperature. After the deposition, the substrate temperature was increased to 100, 200, and 300∘C. In the other type, the substrate temperature was held fixed at some value during the deposition. For this type, the substrate temperatures used were 100, 200, 300, 400, 500, 550, and 600∘C. The samples were characterized in situ by the technique of X-ray photoelectron spectroscopy. No trace of elemental hafnium is observed in the deposited overlayer. Also, there is no evidence of any chemical reactivity between the overlayer and the silicon substrate over the temperature range used. The hafnium overlayer shows a mixture of the dioxide and the suboxide. The ratio of the suboxide to dioxide is observed to be more in the first type of samples. The spectral data indicate that hafnium has a strong affinity for oxygen. The overlayer gets completely oxidized to form HfO2 at substrate temperature around 300∘C for the first type of samples and at substrate temperature greater than 550∘C for the second type.
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39

GÖTHELID, M., B. AUFRAY, H. GIORDANO, J. M. Gay, G. LE LAY, R. Belkhou, N. Marsot et C. Guillot. « Sb/Cu(111) : GROWTH, DISSOLUTION AND SEGREGATION STUDIED BY AES, LEED and PES ». Surface Review and Letters 04, no 06 (décembre 1997) : 1203–7. http://dx.doi.org/10.1142/s0218625x97001541.

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The room temperature deposition of Sb on to Cu (111) gives rise to two different Sb states as seen from the Sb 4d shallow core level: an adstate similar to the [Formula: see text] structure formed after annealing at 400°C, and an overlayer of unreacted Sb . The unreacted Sb overlayer is rapidly dissolved into a subsurface position in the crystal during annealing, where it forms a quasistable structure which is dissolved very slowly.
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40

Beatty, Marissa, Alexis T. Haley, Nicole Llewelyn et Daniel V. Esposito. « Enhancing Alcohol Oxidation Activity Using Carbon-Modified Silicon Oxide Encapsulated Pt Electrodes ». ECS Meeting Abstracts MA2022-01, no 45 (7 juillet 2022) : 1901. http://dx.doi.org/10.1149/ma2022-01451901mtgabs.

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The performance of direct alcohol fuel cells (DAFCs) is frequently constrained by the efficiencies of the electrocatalysts used for the necessary alcohol oxidation reactions (AORs), which require high overpotentials to remove poisoning CO intermediates from the catalyst surface. Silicon Oxide (SiOx) encapsulated Pt electrodes have previously been shown to reduce the potential required to remove CO, and greatly enhance the activity of Pt-based catalysts for alcohol oxidation. To better understand the mechanism of this enhancement, silicon oxide layers with varying concentrations of residual carbon were employed to probe the compositional effects of overlayer composition on AORs. Overall, it was found that carbon-free, SiOx encapsulated samples exhibited the largest reduction in CO oxidation potential, with carbon rich samples still demonstrating a slight decrease in required potential compared to unencapsulated, bare Pt. Surprisingly, samples that demonstrated the largest reductions in CO oxidation potentials did not show the highest activity enhancement for alcohol oxidation. Instead, samples that had the highest concentration of carbon showed the highest degree of current enhancement for formic acid, methanol, and ethanol oxidation. For larger alcohols like propanol and butanol, the measured activity for alcohol oxidation on encapsulated samples began to diminish, credited to the additional mass transport resistance that the overlayer introduces. These observations offer insights into how the composition and properties of SiOx overlayers can affect the reactivity and transport of species in an electrochemical system, and offer an additional level of design for the development of future electrocatalyst architectures.
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41

Pašti, Igor A., Nemanja M. Gavrilov et Slavko V. Mentus. « Hydrogen Adsorption on Palladium and Platinum Overlayers : DFT Study ». Advances in Physical Chemistry 2011 (10 juillet 2011) : 1–8. http://dx.doi.org/10.1155/2011/305634.

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Hydrogen adsorption on twenty different palladium and platinum overlayer surfaces with (111) crystallographic orientation was studied by means of periodic DFT calculations on the GGA-PBE level. Palladium and platinum overlayers here denote either the Pd and Pt mono- and bilayers deposited over (111) crystallographic plane of Pd, Pt, Cu, and Au monocrystals or the (111) crystallographic plane of Pd and Pt monocrystals with inserted one-atom-thick surface underlayer of Pd, Pt, Cu, and Au. The attention was focused on the bond lengths, hydrogen adsorption energetics, mobility of adsorbed hydrogen, and surface reactivity toward hydrogen electrode reactions. Both the ligand and strain effects were considered, found to lead to a significant modification of the electronic structure of Pd and Pt overlayers, described through the position of the d-band center, and tuning of the hydrogen adsorption energy in the range that covers approximately 120 kJmol−1. Mobility of hydrogen adsorbed on studied overlayers was found to be determined by hydrogen-metal binding energy. Obtained results regarding Pd layers on Pt(111) and Au(111) surfaces, in conjunction with some of the recent experimental data, were used to explain its electrocatalytic activity towards hydrogen evolution reaction.
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42

Fechtchenko, R. M., et A. V. Vinogradov. « Reflection from surfaces with a thin overlayer ». Optics Letters 25, no 14 (15 juillet 2000) : 998. http://dx.doi.org/10.1364/ol.25.000998.

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43

AOKI, Junichi, et Hitoshi YASUNAGA. « Surface electromigration of Cu overlayer on Si. » Hyomen Kagaku 10, no 5 (1989) : 364–68. http://dx.doi.org/10.1380/jsssj.10.364.

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44

Chang, S., A. Rizzi, C. Caprile, P. Philip, A. Wall et A. Franciosi. « Overlayer‐induced enhanced oxidation of GaAs surfaces ». Journal of Vacuum Science & ; Technology A : Vacuum, Surfaces, and Films 4, no 3 (mai 1986) : 799–805. http://dx.doi.org/10.1116/1.573818.

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Ishino, Yuichi, et Hatsuo Ishida. « Grazing Angle Metal-Overlayer Infrared ATR Spectroscopy ». Applied Spectroscopy 42, no 7 (septembre 1988) : 1296–302. http://dx.doi.org/10.1366/0003702884429959.

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The most sensitive reflection spectroscopic technique has been developed for studying the structure of thin films between a semiconductor and a metallic film. In this study, a metal-overlayer ATR technique was applied to measure the infrared spectra of interfacial layers. According to optical theory, this technique requires a high angle of incidence near the grazing angle in order to obtain optimum sensitivity. On the basis of the theoretical prediction, an optimized prism was designed. Our prism/thin film/ metal configuration yields an S/N ratio 5 times better than that achieved by the conventional reflection-absorption spectroscopy. This enhancement is not due to the so-called metal island effect, but is due instead to the high refractive index of the semiconductor prism.
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Chan, C. T., J. G. Che et T. C. Leung. « First principles studies of overlayer-induced faceting ». Progress in Surface Science 59, no 1-4 (septembre 1998) : 1–11. http://dx.doi.org/10.1016/s0079-6816(98)00032-x.

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Zinke-Allmang, M., et L. C. Feldman. « Overlayer energetics from thermal desorption on Si ». Surface Science 191, no 1-2 (janvier 1987) : L749—L755. http://dx.doi.org/10.1016/s0039-6028(87)81034-8.

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Lu-Jun, Chen, Wang Ning et Luo Enze. « Jellium sphere model in overlayer-substrate systems ». Journal de Physique I 3, no 4 (avril 1993) : 1053–58. http://dx.doi.org/10.1051/jp1:1993176.

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49

Kroll, G. H., T. R. Ohno et J. H. Weaver. « Nondisruptive oxide overlayer growth on GaAs(110) ». Applied Physics Letters 58, no 20 (20 mai 1991) : 2249–51. http://dx.doi.org/10.1063/1.104941.

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Sachtler, Wolfgang M. H., et Yin-Yan Huang. « Metal/overlayer and encaged carbonyl cluster catalysis ». Applied Catalysis A : General 191, no 1-2 (janvier 2000) : 35–44. http://dx.doi.org/10.1016/s0926-860x(99)00303-8.

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