The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Giuliano Moretti - One of the best experts on this subject based on the ideXlab platform.
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Auger Parameters and Wagner plots
Journal of Electron Spectroscopy and Related Phenomena, 2020Co-Authors: Mauro Satta, Giuliano MorettiAbstract:A brief review on the use of Auger Parameters and Wagner plots (chemical-state plots) in the characterization of surfaces by XPS is presented with particular reference on their applications to barium compounds. Computational (Tinker) and computer graphic (Molden) programs, available free of charge from the web permit, respectively, the calculation of Auger Parameter Shifts at the electrostatical level of theory and the graphical display of the atomic structures involved. An application of these methods is reported for a BaCl(2) crystal, considering the Auger Parameter Shift of Ba(2+) ions in different localizations. The effects of distant cations and anions from the ion with the core hole may be easily investigated together with the effect of decreasing the coordination number of an ion because of its localization at the surface of the material. For such an ion, the effect of adsorbed molecules (e.g. water and hydrogen sulfide molecules) on the Auger Parameter Shift can also be calculated. The initial- and final-state effects determine the localization of a barium compound in the Wagner plot which is a very useful tool in the chemical-state analysis. (C) 2009 Elsevier B.V. All rights reserved
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Auger Parameters and Wagner plots
Journal of Electron Spectroscopy and Related Phenomena, 2010Co-Authors: Mauro Satta, Giuliano MorettiAbstract:Abstract A brief review on the use of Auger Parameters and Wagner plots (chemical-state plots) in the characterization of surfaces by XPS is presented with particular reference on their applications to barium compounds. Computational (Tinker) and computer graphic (Molden) programs, available free of charge from the web permit, respectively, the calculation of Auger Parameter Shifts at the electrostatical level of theory and the graphical display of the atomic structures involved. An application of these methods is reported for a BaCl 2 crystal, considering the Auger Parameter Shift of Ba 2+ ions in different localizations. The effects of distant cations and anions from the ion with the core hole may be easily investigated together with the effect of decreasing the coordination number of an ion because of its localization at the surface of the material. For such an ion, the effect of adsorbed molecules (e.g. water and hydrogen sulfide molecules) on the Auger Parameter Shift can also be calculated. The initial- and final-state effects determine the localization of a barium compound in the Wagner plot which is a very useful tool in the chemical-state analysis.
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Long range and surface effects on the Auger Parameter : electrostatic self-consistent polarization energy model
Surface and Interface Analysis, 2008Co-Authors: Mauro Satta, Simone Morpurgo, Giuliano MorettiAbstract:Computational (Tinker) and computer graphic (Molden) programs, available free of charge from the web, respectively, permit the calculation of Auger Parameter Shifts at the electrostatical level of theory and the graphical display of the involved atomic structures. The effects of distant cations and anions from the ion with the added positive charge may be easily investigated together with the effect of decreasing its coordination number because of its localization at the surface of the material. For such an ion, the effect of adsorbed molecules (e.g. water molecules) on the Auger Parameter Shift can also be calculated. An application of this method is reported for a BaCl 2 crystal considering the Auger Parameter Shift of Ba cations in different localizations.
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Auger Parameter and Wagner plot in the characterization of chemical states by X-ray photoelectron spectroscopy: a review
Journal of Electron Spectroscopy and Related Phenomena, 1998Co-Authors: Giuliano MorettiAbstract:Abstract In this review we describe the Auger Parameter concept and its relation to the final state relaxation energy. After a historical introduction we illustrate the several models proposed to calculate relaxation energies and Auger Parameter Shifts. It is stressed how the initial empirical approach of the Auger Parameter concept developed by Wagner in the early 1970s is now changed thanks to the elaboration of theoretical models based on classical electrostatic and quantum chemistry. The Auger Parameter permits to obtain information on the local chemical environment of core-ionized atoms. Even more information can be obtained arranging photoemission and Auger lines in the format of the so called Wagner plots (chemical state plots). These plots contain information on the initial state effects, i.e. the Madelung potential and the ground state valence atomic charge at the core-ionized atom, and on the final state relaxation energy. By means of the point–charge potential approximation, the Auger Parameter and the Wagner plot, we describe a simple semiquantitative model useful to rationalize the dependence of the local electronic structure on the atomic environment. The Auger Parameter is useful to study the screening mechanism in the final state of the photoemission process. In the case of the non-local screening mechanism (polarization of the charge from the nearest-neighbour ligands towards extended empty orbitals of the core-ionized atom) a simple electrostatic model permits the estimation of the Auger Parameter Shifts. It is shown that the Auger Parameter Shift is a function of the number, distance, electronic polarizability and local geometry of the nearest-neighbour ligands around the core-ionized atom. The electrostatic model has been applied successfully for interpreting Auger Parameter Shifts of core-ionized atoms in insulators and semiconductors compounds. On the other hand, when the electrostatic model cannot be applied, as in the case of the local screening mechanism (complete tranfer of one electron towards empty and localized orbitals of the core-ionized atom), the extended potential model of the Auger Parameter is able to relate the potential in an atomic core to the atomic valence charge. According to this model the Auger Parameter Shift depends on atomic properties of the core-ionized atom, obtained from atomic structure calculations, on the valence charge in the initial state and on the screening charge in the final state. It has been applied successfully for interpreting metal-free atom and alloy–pure metal Auger Parameter Shifts. Other models of the Auger Parameter based on electrostatics, quantum chemistry and thermochemistry are also reviewed.
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Auger Parameter and Wagner plot in the characterization of chemical states by X-ray photoelectron spectroscopy: a review
Journal of Electron Spectroscopy and Related Phenomena, 1998Co-Authors: Giuliano MorettiAbstract:In this review we describe the Auger Parameter concept and its relation to the final state relaxation energy. After a historical introduction we illustrate the several models proposed to calculate relaxation energies and Auger Parameter Shifts. It is stressed how the initial empirical approach of the Anger Parameter concept developed by Wagner in the early 1970s is now changed thanks to the elaboration of theoretical models based on classical electrostatic and quantum chemistry. The Auger Parameter permits to obtain information on the local chemical environment of core-ionized atoms. Even more information can be obtained arranging photoemission and Auger lines in the format of the so called Wagner plots (chemical state plots). These plots contain information an the initial state effects, i.e. the Madelung potential and the ground state valence atomic charge at the core-ionized atom, and on the final state relaxation energy. By means of the point-charge potential approximation, the Auger Parameter and the Wagner plot, we describe a simple semiquantitative model useful to rationalize the dependence of the local electronic structure on the atomic environment. The Auger Parameter is useful to study the screening mechanism in the final state of the photoemission process. In the case of the non-local screening mechanism (polarization of the charge from the nearest-neighbour ligands towards extended empty orbitals of the core-ionized atom) a simple electrostatic model permits the estimation of the Auger Parameter Shifts. It is shown that the Auger Parameter Shift is a function of the number, distance, electronic polarizability and local geometry of the nearest-neighbour ligands around the core-ionized atom. The electrostatic model has been applied successfully for interpreting Auger Parameter Shifts of core-ionized atoms in insulators and semiconductors compounds. On the other hand, when the electrostatic model cannot be applied, as in the case of the local screening mechanism (complete tranfer of one electron towards empty and localized orbitals of the core-ionized atom), the extended potential model of the Auger Parameter is able to relate the potential in an atomic core to the atomic valence charge. According to this model the Auger Parameter Shift depends on atomic properties of the core-ionized atom, obtained from atomic structure calculations, on the valence charge in the initial state and on the screening charge in the final state. It has been applied successfully for interpreting metal-free atom and alloy-pure metal Auger Parameter Shifts. Other models of the Auger Parameter based on electrostatics, quantum chemistry and thermochemistry are also reviewed. (C) 1998 Elsevier Science B.V. All rights reserved
S. Subbanna - One of the best experts on this subject based on the ideXlab platform.
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Wafer level forward current reliability analysis of 120GHz production SiGe HBTs under accelerated current stress
2002 IEEE International Reliability Physics Symposium. Proceedings. 40th Annual (Cat. No.02CH37320), 2002Co-Authors: J.-s. Rieh, K. Watson, F. Guarin, Z. Yang, P.-c. Wang, A. Joseph, G. Freeman, S. SubbannaAbstract:A wafer-level reliability (WLR) technique is presented to assess the forward current mode degradation of polysilicon emitter bipolar transistors. Using this technique, we show results for the first time on degradation properties of high-speed self-aligned SiGe HBTs featuring 120 GHz f/sub T/ and 100 GHz f/sub max/. Accelerated current stress up to as high as J/sub C/=34 mA//spl mu/m/sup 2/ was employed to assess the device degradation. It is shown that current accelerated stress may be used to effectively predict Shifts in device characteristics. No catastrophic failures were observed, and thus this technique is used principally to demonstrate parametric Shifts rather than end-of-life failures. Since the current stress also involves substantial self-heating of the device, we compare the degradation with temperature-only acceleration at both wafer and module level. It was found that the current acceleration is dominant over the temperature acceleration in the observable mechanisms. The mechanism for the parametric Shifts is believed to be related to interfacial properties between the polysilicon and single-crystal portions of the device emitter. Through these studies, it is shown that the device is highly robust to parametric Shifts for over 10/sup 6/ hours. The comparison with module level stress results verified their consistency with wafer level stressing, thus providing a viable WLR methodology for Parameter Shift projection in a relatively short stress time and moderate temperature.
Z.h Ma - One of the best experts on this subject based on the ideXlab platform.
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Auger Parameter Shift and extra-atomic-relaxation of ZnS1−xTex alloys
Journal of Crystal Growth, 2020Co-Authors: J.w.l Wong, Z.h MaAbstract:Auger Parameter Shifts of Zn and Te as a function of composition of 3 relatively unexplored semi-insulator ZnS1-xTex alloy system were studied using X-ray photoelectron spectroscopy (XPS). A model based on the concept of relaxation is used to explain the polarization change of this alloy system due to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS1-xTex alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement. (C) 2001 Elsevier Science B.V. All rights reserved
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XPS studies of Auger Parameter Shift of ZnS1–xTex alloys
Journal of Electron Spectroscopy and Related Phenomena, 2020Co-Authors: J.w.l Wong, Z.h MaAbstract:X-ray photoelectron spectroscopy (XPS) was used to study the photoelectron emission of a relatively unexplored semi-insulator ZnS1-xTex alloy system. The investigation was focused on the Auger Parameter Shifts of Zn and Te as a function of composition. Taking into account the alloy disordering and the semi-insulating characteristics of the ZnS1-xTex alloy system, a model based on the concept of relaxation is used to explain the polarization change of this alloy system dud to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS1-xTex alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement. (C) 2001 Elsevier Science B.V. All rights reserved
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XPS studies of Auger Parameter Shift of ZnS1–xTex alloys
Journal of Electron Spectroscopy and Related Phenomena, 2001Co-Authors: J.w.l Wong, Z.h MaAbstract:Abstract X-ray photoelectron spectroscopy (XPS) was used to study the photoelectron emission of a relatively unexplored semi-insulator ZnS 1– x Te x alloy system. The investigation was focused on the Auger Parameter Shifts of Zn and Te as a function of composition. Taking into account the alloy disordering and the semi-insulating characteristics of the ZnS 1– x Te x alloy system, a model based on the concept of relaxation is used to explain the polarization change of this alloy system due to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS 1– x Te x alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement.
J.w.l Wong - One of the best experts on this subject based on the ideXlab platform.
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XPS studies of Auger Parameter Shift of ZnS1–xTex alloys
Journal of Electron Spectroscopy and Related Phenomena, 2020Co-Authors: J.w.l Wong, Z.h MaAbstract:X-ray photoelectron spectroscopy (XPS) was used to study the photoelectron emission of a relatively unexplored semi-insulator ZnS1-xTex alloy system. The investigation was focused on the Auger Parameter Shifts of Zn and Te as a function of composition. Taking into account the alloy disordering and the semi-insulating characteristics of the ZnS1-xTex alloy system, a model based on the concept of relaxation is used to explain the polarization change of this alloy system dud to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS1-xTex alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement. (C) 2001 Elsevier Science B.V. All rights reserved
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Auger Parameter Shift and extra-atomic-relaxation of ZnS1−xTex alloys
Journal of Crystal Growth, 2020Co-Authors: J.w.l Wong, Z.h MaAbstract:Auger Parameter Shifts of Zn and Te as a function of composition of 3 relatively unexplored semi-insulator ZnS1-xTex alloy system were studied using X-ray photoelectron spectroscopy (XPS). A model based on the concept of relaxation is used to explain the polarization change of this alloy system due to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS1-xTex alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement. (C) 2001 Elsevier Science B.V. All rights reserved
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auger Parameter Shift and extra atomic relaxation of zns1 xtex alloys
Journal of Crystal Growth, 2001Co-Authors: J.w.l Wong, Z HAbstract:Abstract Auger Parameter Shifts of Zn and Te as a function of composition of a relatively unexplored semi-insulator ZnS 1− x Te x alloy system were studied using X-ray photoelectron spectroscopy (XPS). A model based on the concept of relaxation is used to explain the polarization change of this alloy system due to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS 1− x Te x alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement.
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Auger Parameter Shift and extra-atomic-relaxation of ZnS1−xTex alloys
Journal of Crystal Growth, 2001Co-Authors: J.w.l Wong, Z HAbstract:Abstract Auger Parameter Shifts of Zn and Te as a function of composition of a relatively unexplored semi-insulator ZnS 1− x Te x alloy system were studied using X-ray photoelectron spectroscopy (XPS). A model based on the concept of relaxation is used to explain the polarization change of this alloy system due to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS 1− x Te x alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement.
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XPS studies of Auger Parameter Shift of ZnS1–xTex alloys
Journal of Electron Spectroscopy and Related Phenomena, 2001Co-Authors: J.w.l Wong, Z.h MaAbstract:Abstract X-ray photoelectron spectroscopy (XPS) was used to study the photoelectron emission of a relatively unexplored semi-insulator ZnS 1– x Te x alloy system. The investigation was focused on the Auger Parameter Shifts of Zn and Te as a function of composition. Taking into account the alloy disordering and the semi-insulating characteristics of the ZnS 1– x Te x alloy system, a model based on the concept of relaxation is used to explain the polarization change of this alloy system due to the existence of the two core holes left in the Auger process. To complement this theoretical model, the dielectric constants of ZnS 1– x Te x alloys as a function of composition were measured using a structure similar to a parallel plate capacitor. The Auger Parameter Shifts calculated from this model are in good agreement with that obtained from the XPS measurement.
J.-s. Rieh - One of the best experts on this subject based on the ideXlab platform.
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Wafer level forward current reliability analysis of 120GHz production SiGe HBTs under accelerated current stress
2002 IEEE International Reliability Physics Symposium. Proceedings. 40th Annual (Cat. No.02CH37320), 2002Co-Authors: J.-s. Rieh, K. Watson, F. Guarin, Z. Yang, P.-c. Wang, A. Joseph, G. Freeman, S. SubbannaAbstract:A wafer-level reliability (WLR) technique is presented to assess the forward current mode degradation of polysilicon emitter bipolar transistors. Using this technique, we show results for the first time on degradation properties of high-speed self-aligned SiGe HBTs featuring 120 GHz f/sub T/ and 100 GHz f/sub max/. Accelerated current stress up to as high as J/sub C/=34 mA//spl mu/m/sup 2/ was employed to assess the device degradation. It is shown that current accelerated stress may be used to effectively predict Shifts in device characteristics. No catastrophic failures were observed, and thus this technique is used principally to demonstrate parametric Shifts rather than end-of-life failures. Since the current stress also involves substantial self-heating of the device, we compare the degradation with temperature-only acceleration at both wafer and module level. It was found that the current acceleration is dominant over the temperature acceleration in the observable mechanisms. The mechanism for the parametric Shifts is believed to be related to interfacial properties between the polysilicon and single-crystal portions of the device emitter. Through these studies, it is shown that the device is highly robust to parametric Shifts for over 10/sup 6/ hours. The comparison with module level stress results verified their consistency with wafer level stressing, thus providing a viable WLR methodology for Parameter Shift projection in a relatively short stress time and moderate temperature.