The Experts below are selected from a list of 50097 Experts worldwide ranked by ideXlab platform
Leonard C. Feldman - One of the best experts on this subject based on the ideXlab platform.
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Ion Scattering simulatIons of the Si(100)-SiO2 interface
Physical Review B, 2006Co-Authors: Angelo Bongiorno, Alfredo Pasquarello, Mark S. Hybertsen, Leonard C. FeldmanAbstract:We carry out Ion Scattering simulatIons to investigate the nature of the transitIon regIon at the Si(100)-SiO2 interface. Ion Scattering experiments performed in the channeling geometry provide us with a genuine interfacial property, the excess Si yield, resulting from distortIons in the Si substrate and from Si atoms in intermediate oxidatIon states. To interpret the Ion Scattering data, we first generate a series of model structures for the interface by applying sequentially classical molecular dynamics and density-functIonal relaxatIon methods. These models reproduce atomic-scale features consistent with a variety of available experimental data. Then, we design a classical scheme to perform Ion Scattering simulatIons on these model interfaces. In our study, we separate the excess Si yield obtained from experiments in two distinct contributIons. First, Si atoms in intermediate oxidatIon states account for similar to 25% of the excess Si yield, a contributIon that is fully determined by the populatIon of suboxide determined from photoemissIon data. The remaining similar to 75% of the excess Si yield characterizes the amount of lateral distortIon of the substrate Si layers in the vicinity of the Si(100)-SiO2 interface. The comparison between calculated and experimental excess Si yields indicates that the distortIons propagating from the interface into the Si substrate are consistent with interfacial transitIon structures extending over more than two Si layers, eventually including a disordered bonding pattern. Nearly abrupt interfaces induce distortIons in the upper layers of the Si substrate which are insufficient for reproducing the experimental excess Si yields.
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Silicon crystal distortIons at the Si(100)-SiO 2 interface from analysis of Ion-Scattering
Microelectronic Engineering, 2004Co-Authors: Angelo Bongiorno, Alfredo Pasquarello, Mark S. Hybertsen, Leonard C. FeldmanAbstract:The structure of the Si(100)-SiO2 interface is investigated at the atomic scale by combining Rutherford Ion Scattering measurements and theoretical modeling. Ion-Scattering experiments are performed in the channeling geometry using Ion energies between 0.4 and 2.0 MeV. These measurements are sensitive to Si displacements at the interface between 0.07 and 0.14 A. To interpret our experimental results, we perform Ion-Scattering simulatIons on two realistic model structures of the Si(100)-SiO2 interface. The comparison between experiment and simulatIon over the full range of considered Ion energies supports a Si(100)-SiO2 interface model presenting a disordered pattern of Si-Si dimers in the transitIon regIon.
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high resolutIon Ion Scattering study of silicon oxynitridatIon
Applied Physics Letters, 1996Co-Authors: E P Gusev, Leonard C. Feldman, Eric Garfunkel, Torgny Gustafsson, M L Green, D BrasenAbstract:High resolutIon medium energy Ion Scattering was used to characterize the nitrogen distributIon in ultrathin silicon oxynitrides with sub‐nm‐accuracy. We show that nitrogen does not incorporate into the subsurface regIon of the substrate after oxidatIon of Si(100) in NO. Core‐level photoemissIon experiments show two bonding configuratIons of nitrogen near the interface. OxynitridatIon in N2O results in a lower concentratIon and a broader distributIon of nitrogen than in the NO case.
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High energy Ion Scattering
Surface Science, 1994Co-Authors: Leonard C. FeldmanAbstract:Abstract High energy Ion Scattering has emerged as an important tool in the arsenal of surface science. This paper briefly reviews some of the underlying physics of the Ion Scattering/surface probe and describes the history and accomplishments of the technique.
T. C. Q. Noakes - One of the best experts on this subject based on the ideXlab platform.
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Optical and Ion-Scattering study of SiO2 layers thermally grown on 4H-SiC
Semiconductor Science and Technology, 2002Co-Authors: D J Hayton, Paul Bailey, T E Jenkins, T. C. Q. NoakesAbstract:Medium energy Ion Scattering, Fourier transform infrared spectroscopy and spectroscopic ellipsometry measurements have been performed on thermally grown SiO2 layers on 4H silicon carbide. The data suggest the presence of a layer at the oxide–SiC interface consisting of both disordered Si and C. The infrared data indicate that the oxide layer is denser than fused silica. The thickness of the oxide layers as measured by spectroscopic ellipsometry agrees well with the values obtained from Ion Scattering.
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Monolayer resolutIon in medium energy Ion Scattering
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2001Co-Authors: Paul Bailey, T. C. Q. Noakes, Christopher J. Baddeley, S. P. Tear, D.p. WoodruffAbstract:Although medium energy Ion Scattering (MEIS) could be considered to be a mature technique, it continues to find new applicatIons and new methodologies, especially in exploiting the monolayer resolutIon capabilities. In this paper we consider four applicatIons which provide informatIon with monolayer resolutIon and illustrate each with a practical example.
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Indium segregatIon in MOCVD InGaN layers studied by medium energy Ion Scattering
Diamond and Related Materials, 2000Co-Authors: Paul R. Chalker, Paul Bailey, T. C. Q. Noakes, D.e. Morrice, T.b. Joyce, L. ConsidineAbstract:The long term stability of InGaN based light emitting- and laser-diodes is potentially compromised by phase separatIon and indium interdiffusIon. Medium energy Ion Scattering has been used to investigate the diffusIon of indium within In0.25Ga0.75N/GaN structures at 950°C. Comparison of the aligned and random Ion Scattering data for the as-deposited InGaN layer show that ca. 15% of the indium atoms are interstitial. Annealing at 950°C causes decompositIon of the InGaN layer into InN and a range of lower indium content ternary phases.
Edmund Taglauer - One of the best experts on this subject based on the ideXlab platform.
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A low-energy Ion Scattering study of Al(110) surface melting
Surface Science, 2003Co-Authors: L. Pedemonte, Edmund Taglauer, Gianangelo Bracco, A. Robin, R. Beikler, W. HeilandAbstract:Abstract The thermal behaviour of the (1 1 0) surface of aluminum is investigated by low-energy Ion Scattering along the 〈1 1 0〉 and 〈0 0 1〉 azimuthal directIons in the temperature range between 300 and 910 K. Surface channeling mode and neutral impact collisIon Ion Scattering spectroscopy are used. Surface melting is observed and informatIon on the evolutIon of the surface structure is gained with the help of simulatIons performed with the MARLOWE code. Experimental evidence for residual short range order is obtained along both azimuths within the quasi-liquid layer which probably consists of groups of surface atoms in correlated motIon.
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Low-energy Ion Scattering at surfaces
Surface Science Reports, 1993Co-Authors: Horst Niehus, Werner Heiland, Edmund TaglauerAbstract:Abstract The field of low-energy Ion Scattering for surface interactIons at metals, alloys, catalysts and semiconductors is reviewed. The descriptIon of experimental set-up's for Ion and neutral detectIon has been included. One of the topics is Ion Scattering for elemental analysis of the topmost layer to be performed in the classical noble-gas Ion Scattering spectroscopy approach (ISS) as well as with direct recoil spectroscopy (DRS). Emphasis has also been put on surface structure analysis including Ion beam crystallography with low-energy Ion backScattering (ICISS) for single-crystal surfaces. The basic principles, classical Scattering theory, the effect of shadowing and blocking, and some of the computer simulatIon programs are briefly described. A discussIon for understanding the physics of Ion-surface interactIons, charge exchange of various projectiles during collisIons, molecule Scattering and bond breaking is also included.
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Surface CharacterizatIon: A User's Sourcebook - Ion Scattering Spectroscopy
ASTM special technical publications, 1991Co-Authors: Edmund Taglauer, Al W. Czanderna, David M HerculesAbstract:Surface characterizatIon by Ion Scattering spectroscopy means the determinatIon of the atomic masses and their geometric arrangement on a solid surface. A low-energy Ion beam is a well-suited probe for such investigatIons because of the strong interactIon between the Ions in the considered energy regime and the surface atoms. “Low-energy” here refers to a range from a few hundred electron volts up to several keV. There are some essential features of Ion Scattering spectroscopy (ISS) or low-energy Ion Scattering (LEIS) which define its usefulness as a surface analytical method.
Angelo Bongiorno - One of the best experts on this subject based on the ideXlab platform.
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Ion Scattering simulatIons of the Si(100)-SiO2 interface
Physical Review B, 2006Co-Authors: Angelo Bongiorno, Alfredo Pasquarello, Mark S. Hybertsen, Leonard C. FeldmanAbstract:We carry out Ion Scattering simulatIons to investigate the nature of the transitIon regIon at the Si(100)-SiO2 interface. Ion Scattering experiments performed in the channeling geometry provide us with a genuine interfacial property, the excess Si yield, resulting from distortIons in the Si substrate and from Si atoms in intermediate oxidatIon states. To interpret the Ion Scattering data, we first generate a series of model structures for the interface by applying sequentially classical molecular dynamics and density-functIonal relaxatIon methods. These models reproduce atomic-scale features consistent with a variety of available experimental data. Then, we design a classical scheme to perform Ion Scattering simulatIons on these model interfaces. In our study, we separate the excess Si yield obtained from experiments in two distinct contributIons. First, Si atoms in intermediate oxidatIon states account for similar to 25% of the excess Si yield, a contributIon that is fully determined by the populatIon of suboxide determined from photoemissIon data. The remaining similar to 75% of the excess Si yield characterizes the amount of lateral distortIon of the substrate Si layers in the vicinity of the Si(100)-SiO2 interface. The comparison between calculated and experimental excess Si yields indicates that the distortIons propagating from the interface into the Si substrate are consistent with interfacial transitIon structures extending over more than two Si layers, eventually including a disordered bonding pattern. Nearly abrupt interfaces induce distortIons in the upper layers of the Si substrate which are insufficient for reproducing the experimental excess Si yields.
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Silicon crystal distortIons at the Si(100)-SiO 2 interface from analysis of Ion-Scattering
Microelectronic Engineering, 2004Co-Authors: Angelo Bongiorno, Alfredo Pasquarello, Mark S. Hybertsen, Leonard C. FeldmanAbstract:The structure of the Si(100)-SiO2 interface is investigated at the atomic scale by combining Rutherford Ion Scattering measurements and theoretical modeling. Ion-Scattering experiments are performed in the channeling geometry using Ion energies between 0.4 and 2.0 MeV. These measurements are sensitive to Si displacements at the interface between 0.07 and 0.14 A. To interpret our experimental results, we perform Ion-Scattering simulatIons on two realistic model structures of the Si(100)-SiO2 interface. The comparison between experiment and simulatIon over the full range of considered Ion energies supports a Si(100)-SiO2 interface model presenting a disordered pattern of Si-Si dimers in the transitIon regIon.
Hh Hidde Brongersma - One of the best experts on this subject based on the ideXlab platform.
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CharacterizatIon of Materials - Low-energy Ion Scattering
Characterization of Materials, 2012Co-Authors: Hh Hidde Brongersma, S.n. Ermolov, V.g. GlebovskyAbstract:Low-energy Ion Scattering (LEIS), also called Ion Scattering spectroscopy (ISS), is a tool for the analysis of the atomic compositIon of the surface as well as for a nondestructive in-depth analysis of the near surface (0–10 nm). The analysis is based on backScattering of noble gas Ions (He+, Ne+, Ar+, or Kr+) in the range of a few hundred to 10,000 eV. The extreme surface sensitivity of LEIS enables the selective analysis of the outermost atomic layer. This is precisely the layer that is largely responsible for many chemical and physical properties of materials. In combinatIon with sputter depth profiling LEIS can also be used for the analysis of much deeper layers. Recent advances in the development of LEIS instruments now allow an essentially nondestructive (“static”) analysis, even of very sensitive materials like organic films. With the modern LEIS instruments one can analyze very rough amorphous insulating samples just as easily as conducting flat single crystals. The only restrictIon for samples being, that they can be put into vacuum for analysis. The applicatIons of LEIS are, therefore, very wide and include important processes like adhesIon, catalysis, diffusIon, film growth, and electron emissIon. Alternative techniques include surface science tools, in particular X-ray photoelectron spectroscopy (XPS), (TOF-) SIMS, the high-energy Ion Scattering techniques (HEIS), and medium-energy Ion Scattering, MEIS. Keywords: low-energy Ion Scattering; LEIS; ISS; surface; depth profile; atomic compositIon
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High-sensitivity and high-resolutIon low-energy Ion Scattering
Vacuum, 2010Co-Authors: Hh Hidde Brongersma, Thomas Grehl, Paul A. Van Hal, Niels C.w. Kuijpers, Simon G. J. Mathijssen, Emma R. Schofield, Richard A.p. Smith, Hendrik R. J. Ter VeenAbstract:Abstract Low-Energy Ion Scattering (LEIS or ISS) is used to selectively analyze the atomic compositIon of the outer atomic layer of surfaces. In additIon, the spectrum gives (non-destructively) the in-depth distributIon. Using a double toroidal energy analyzer with parallel energy detectIon and time-of-flight filtering a high sensitivity and mass resolutIon of LEIS is achieved. This is demonstrated for a highly dispersed catalyst of Pt/Au on γ-alumina. The improved depth resolutIon is illustrated for self-assembled monolayers of alkanethiols (12–20 carbon atoms) on gold. Even for these low Z carbon atoms a clear shift of 8 eV/carbon atom is observed (using 1.5 keV 4 He + Ion Scattering). This opens many new possibilities for studies of ultra-thin diffusIon barriers, high-k dielectrics and biosensors.
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Insight in the outside: New applicatIons of low-energy Ion Scattering
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2002Co-Authors: Hh Hidde Brongersma, Anja Gildenpfennig, Arnoud Denier Van Der Gon, Robert D. Van De Grampel, W.p.a. Jansen, Arie Knoester, Jozua Laven, M. M. ViitanenAbstract:Low energy Ion Scattering is used to selectively probe the outermost atomic layer of the surface. The development of double toroidal analyzers has improved the detectIon sensitivity of low energy Ion Scattering by orders of magnitude. The features of these analyzers are discussed. It is shown that the absence of matrix effects makes it possible to quantify the surface density of fluorine in polymers with a LiF(1 0 0) surface. The extreme surface sensitivity of LEIS also enables one to study intramolecular segregatIon processes. As an example the aging of a polypropylene surface that has been activated with atomic oxygen is described. As an example of the LEIS analysis of highly dispersed isolating surfaces, the formatIon of coke on a commercial three-way catalyst is discussed.
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Crystal-face dependence of low-energy Ion Scattering signals
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2001Co-Authors: R. Cortenraad, S.n. Ermolov, B. Moest, V.g. Glebovsky, Hh Hidde BrongersmaAbstract:Abstract Low-energy Ion Scattering (LEIS) on tungsten single crystals with different crystallographic orientatIons showed that only for the closest packed crystal face, the Ion Scattering signal originates completely from the outermost atomic plane. For various crystallographic orientatIons, we derived the contributIons from the deeper atomic planes to the Ion Scattering signal, and found that for more open surface structures the deeper planes contribute significantly to the signal. For example, for the W(1 1 1) face, only 50% of the Ion Scattering signal is due to Ions Scattering from the outermost atomic plane. The influence of Ion bombardment on the signal intensity of well-ordered crystalline surfaces was also studied, and it was found that Ion bombardment of close-packed high-melting materials (e.g. W) at room temperature leads to a signal decrease of approximately 30% due to the sputter-induced roughness and disorder. The mobility of low-melting materials (e.g. Ag) during Ion bombardment at room temperature results in a smaller sputter-induced roughness and disorder, and a small change in the Ion Scattering signal (5–10%). Surface cleaning by Ion bombardment is a widely applied method, but thus requires a correctIon for the signal loss due to roughness and disorder when a quantitative analysis is performed.
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ApplicatIon of low-energy Ion Scattering to studies of growth
Applied Surface Science, 1994Co-Authors: Hh Hidde Brongersma, J Jean-paul JacobsAbstract:Abstract The possibilities of low-energy Ion Scattering spectroscopy for surface analysis are discussed. By choosing the proper experimental conditIons the structure of single crystal surfaces can be determined very accurately. Furthermore, low-energy Ion Scattering (LEIS) can be used to determine the atomic compositIon of the outermost atomic layer of any (crystalline or not) surface. This extreme surface sensitivity makes LEIS an ideal tool to investigate growth mechanisms. The results for calcined powders of oxidic spinels suggest that only one or two principal planes occur at the surface. This greatly facilitates the interpretatIon and applicatIon of LEIS to growth on powders. Some applicatIons to study the growth mechanism of supported catalysts are presented.
