Cu-Li coatings of Si microstructures are a promising way to develop low-power emitters for next-g... more Cu-Li coatings of Si microstructures are a promising way to develop low-power emitters for next-generation flat-panel displays. However, understanding these structures requires a detailed view of the field-emission process in relation to the physical structure to characterize the source of emission. To accomplish this we have utilized the element-specific imaging capabilities of an x-ray photoemission microscope (XPEEM) to obtain chemical
We have applied x-ray magnetic circular dichroism to investigate the field-induced ferromagnetism... more We have applied x-ray magnetic circular dichroism to investigate the field-induced ferromagnetism in Pd 40 Ni 22.5 Fe 17.5 P 20 alloy. The experiment revealed that both Ni and Fe were in a divalent state and that the magnetic properties of the material were determined by the localized 3d electrons of the transition metals. No clear evidence of Ruderman-Kittel-Kasuya-Yosida-type interaction among magnetic clusters was observed. It is believed that the detailed balance of fundamental spin-orbit and exchange interactions as a function of temperature and applied magnetic field determine the different magnetic properties of the alloy.
Studies of angle-resolved photoemission from an As-rich GaAs͑111͒-2ϫ2 surface have been extended ... more Studies of angle-resolved photoemission from an As-rich GaAs͑111͒-2ϫ2 surface have been extended to off-normal emission. A detailed analysis has been given of spectra taken with photon energies of 20, 23, 25, and 28 eV. The experimentally observed peak dispersion is examined using structure plots by combining free-electron final states with initial states calculated on the basis of linear muffin-tin orbitals. The results are also compared with earlier angle-resolved photoemission studies on the same surface. This enabled us to identify emission features due mainly to surface states and features to which a combination of various transitions, including surface umklapp, may contribute.
Micro-SRIXE (synchrotron-radiation-induced X-ray emission) and micro-XAS (X-ray absorption spectr... more Micro-SRIXE (synchrotron-radiation-induced X-ray emission) and micro-XAS (X-ray absorption spectroscopy) were used to probe the uptake of exogenous metals by cells. The high flux and the sub-micron resolution of the hard X-ray microprobe, offer the experimenter the ability to obtain highly sensitive spatial and structural information of cellular elements. In this work the uptake of carcinogenic Cr(VI) was compared with that of a relatively non-toxic Cr(III) complex by micro-SRIXE mapping of whole cells. High intracellular Cr concentrations were observed in Cr(VI)-treated cells, while no significant Cr uptake was observed for Cr(III)treated cells, as is consistent with uptake studies performed by other techniques. Micro-XANES analysis of Cr(V)and Cr(VI)-treated cells showed that the predominant oxidation product following cellular metabolism was Cr(III). As shown by X-ray microscopic analysis of thin-sectioned cells, however, the reduction of Cr(VI) to Cr(III) did not occur at a fast enough rate to exclude Cr entry into the cell nucleus.
... 2. 10 P. Mijnarends, Phys. Rev. 178, 622 1969. 11 K. Fujiwara and O. Sueoka, J. Phys. Soc. Jp... more ... 2. 10 P. Mijnarends, Phys. Rev. 178, 622 1969. 11 K. Fujiwara and O. Sueoka, J. Phys. Soc. Jpn. 21, 1947 1966. 12 B. Perrin, G. Weisbuch, and A. Libchaber, Phys. Rev. B 1, 1501 1970. 13 G. Kamm, Phys. Rev. B 1, 554 1970. 14 HV Bohm and V. Easterling, Phys. Rev. ...
Results of resonant Auger spectroscopy experiments are presented for Cu, Co, and oxidized AI. Sub... more Results of resonant Auger spectroscopy experiments are presented for Cu, Co, and oxidized AI. Sub-lifetime narrowing of Auger spectra and generation of sub-lifetime narrowed absorption spectra constructed from Auger yield measurements, were observed.
... normal direction is (001 ). The relative position of the free electron final states and the i... more ... normal direction is (001 ). The relative position of the free electron final states and the initial states is determined by the zero of the free electron bands relative to the valence-band maxi-mum, the inner potential E0. The value of ...
... B.F. Usher Department of Electronics Engineering, La Trobe University, Bundoora 8088, Victori... more ... B.F. Usher Department of Electronics Engineering, La Trobe University, Bundoora 8088, Victoria, Australia B.A. Sexton Commonivealth ... head and an eddy current damped, stainless steel spring and viton suspension system. ...
... 1051/jp4 : 200300019 The 2-! DB intermediate-energy scanning X-ray microscope at the APS 1. M... more ... 1051/jp4 : 200300019 The 2-! DB intermediate-energy scanning X-ray microscope at the APS 1. McNulty, D. Paterson, J. Arko, M. Erdmann, SP Frigo\ K. Goetze, P. Ilinski, N. Krapf2, T. Mooney, CC Retch3, APJ Stampfl4, S. Vogt, Y. Wang5 and S. Xu ...
Formation of a common type of Fe-As local bonding in Fe thin films on GaAs surfaces of differing ... more Formation of a common type of Fe-As local bonding in Fe thin films on GaAs surfaces of differing orientation and preparation is evidenced through a common charge transfer at the interface. X-ray absorption studies of unoccupied 3d states for Fe thin films on sputtered GaAs͑100͒ and cleaved GaAs͑110͒ display a similar amount of 3d charge transfer into the GaAs substrate even though the mode of surface preparation leads to reduced intermixing in the ͑100͒ case. Implications of these results for the understanding of the role of the Fe-GaAs interface in both electronic and magnetic properties are discussed.
We present angle-resolved photoelectron spectra and surface state dispersions for the clean, 2ϫ1 ... more We present angle-resolved photoelectron spectra and surface state dispersions for the clean, 2ϫ1 reconstructed (111) and (100) surfaces of diamond. For the (100) surface a surface state is found in the gap of the projected bulk band structure around Ȳ, which has a binding energy of 2.7 eV at Ȳ ͑relative to the Fermi level͒ and a dispersion in the ⌫-Ȳ direction of 0.5 eV, consistent with theory. At ⌫ a surface resonance is observed at 1.4 eV binding energy. No surface states were observed above the valence-band maximum. Our results on the (111) surface show a strongly dispersing surface state that reaches its maximum 0.5 eV below the Fermi level at K. This result implies a gap of at least 0.5 eV in the surface electronic structure, which has consequences for the surface reconstruction in terms of a-bonded chain model. ͓S0163-1829͑97͒03416-4͔
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002
Current knowledge of fine-particle airborne pollution concentrations and constituents with diamet... more Current knowledge of fine-particle airborne pollution concentrations and constituents with diameters below 2.5 µm (PM2.5) is limited. Sources are both natural and man-made. Here we describe two types of experiments performed using the Advanced Light Source (APS) facility at Chicago, and compare the results with PIXE analysis on the same fine particle filters. Firstly, broad beam (2 mm) studies with tuned synchrotron beam energies to help resolve overlapping X-rays and secondly highly focused X-ray beam studies (0.2µm) of individual fine particles from airborne pollution combustion sources.
Cu-Li coatings of Si microstructures are a promising way to develop low-power emitters for next-g... more Cu-Li coatings of Si microstructures are a promising way to develop low-power emitters for next-generation flat-panel displays. However, understanding these structures requires a detailed view of the field-emission process in relation to the physical structure to characterize the source of emission. To accomplish this we have utilized the element-specific imaging capabilities of an x-ray photoemission microscope (XPEEM) to obtain chemical
We have applied x-ray magnetic circular dichroism to investigate the field-induced ferromagnetism... more We have applied x-ray magnetic circular dichroism to investigate the field-induced ferromagnetism in Pd 40 Ni 22.5 Fe 17.5 P 20 alloy. The experiment revealed that both Ni and Fe were in a divalent state and that the magnetic properties of the material were determined by the localized 3d electrons of the transition metals. No clear evidence of Ruderman-Kittel-Kasuya-Yosida-type interaction among magnetic clusters was observed. It is believed that the detailed balance of fundamental spin-orbit and exchange interactions as a function of temperature and applied magnetic field determine the different magnetic properties of the alloy.
Studies of angle-resolved photoemission from an As-rich GaAs͑111͒-2ϫ2 surface have been extended ... more Studies of angle-resolved photoemission from an As-rich GaAs͑111͒-2ϫ2 surface have been extended to off-normal emission. A detailed analysis has been given of spectra taken with photon energies of 20, 23, 25, and 28 eV. The experimentally observed peak dispersion is examined using structure plots by combining free-electron final states with initial states calculated on the basis of linear muffin-tin orbitals. The results are also compared with earlier angle-resolved photoemission studies on the same surface. This enabled us to identify emission features due mainly to surface states and features to which a combination of various transitions, including surface umklapp, may contribute.
Micro-SRIXE (synchrotron-radiation-induced X-ray emission) and micro-XAS (X-ray absorption spectr... more Micro-SRIXE (synchrotron-radiation-induced X-ray emission) and micro-XAS (X-ray absorption spectroscopy) were used to probe the uptake of exogenous metals by cells. The high flux and the sub-micron resolution of the hard X-ray microprobe, offer the experimenter the ability to obtain highly sensitive spatial and structural information of cellular elements. In this work the uptake of carcinogenic Cr(VI) was compared with that of a relatively non-toxic Cr(III) complex by micro-SRIXE mapping of whole cells. High intracellular Cr concentrations were observed in Cr(VI)-treated cells, while no significant Cr uptake was observed for Cr(III)treated cells, as is consistent with uptake studies performed by other techniques. Micro-XANES analysis of Cr(V)and Cr(VI)-treated cells showed that the predominant oxidation product following cellular metabolism was Cr(III). As shown by X-ray microscopic analysis of thin-sectioned cells, however, the reduction of Cr(VI) to Cr(III) did not occur at a fast enough rate to exclude Cr entry into the cell nucleus.
... 2. 10 P. Mijnarends, Phys. Rev. 178, 622 1969. 11 K. Fujiwara and O. Sueoka, J. Phys. Soc. Jp... more ... 2. 10 P. Mijnarends, Phys. Rev. 178, 622 1969. 11 K. Fujiwara and O. Sueoka, J. Phys. Soc. Jpn. 21, 1947 1966. 12 B. Perrin, G. Weisbuch, and A. Libchaber, Phys. Rev. B 1, 1501 1970. 13 G. Kamm, Phys. Rev. B 1, 554 1970. 14 HV Bohm and V. Easterling, Phys. Rev. ...
Results of resonant Auger spectroscopy experiments are presented for Cu, Co, and oxidized AI. Sub... more Results of resonant Auger spectroscopy experiments are presented for Cu, Co, and oxidized AI. Sub-lifetime narrowing of Auger spectra and generation of sub-lifetime narrowed absorption spectra constructed from Auger yield measurements, were observed.
... normal direction is (001 ). The relative position of the free electron final states and the i... more ... normal direction is (001 ). The relative position of the free electron final states and the initial states is determined by the zero of the free electron bands relative to the valence-band maxi-mum, the inner potential E0. The value of ...
... B.F. Usher Department of Electronics Engineering, La Trobe University, Bundoora 8088, Victori... more ... B.F. Usher Department of Electronics Engineering, La Trobe University, Bundoora 8088, Victoria, Australia B.A. Sexton Commonivealth ... head and an eddy current damped, stainless steel spring and viton suspension system. ...
... 1051/jp4 : 200300019 The 2-! DB intermediate-energy scanning X-ray microscope at the APS 1. M... more ... 1051/jp4 : 200300019 The 2-! DB intermediate-energy scanning X-ray microscope at the APS 1. McNulty, D. Paterson, J. Arko, M. Erdmann, SP Frigo\ K. Goetze, P. Ilinski, N. Krapf2, T. Mooney, CC Retch3, APJ Stampfl4, S. Vogt, Y. Wang5 and S. Xu ...
Formation of a common type of Fe-As local bonding in Fe thin films on GaAs surfaces of differing ... more Formation of a common type of Fe-As local bonding in Fe thin films on GaAs surfaces of differing orientation and preparation is evidenced through a common charge transfer at the interface. X-ray absorption studies of unoccupied 3d states for Fe thin films on sputtered GaAs͑100͒ and cleaved GaAs͑110͒ display a similar amount of 3d charge transfer into the GaAs substrate even though the mode of surface preparation leads to reduced intermixing in the ͑100͒ case. Implications of these results for the understanding of the role of the Fe-GaAs interface in both electronic and magnetic properties are discussed.
We present angle-resolved photoelectron spectra and surface state dispersions for the clean, 2ϫ1 ... more We present angle-resolved photoelectron spectra and surface state dispersions for the clean, 2ϫ1 reconstructed (111) and (100) surfaces of diamond. For the (100) surface a surface state is found in the gap of the projected bulk band structure around Ȳ, which has a binding energy of 2.7 eV at Ȳ ͑relative to the Fermi level͒ and a dispersion in the ⌫-Ȳ direction of 0.5 eV, consistent with theory. At ⌫ a surface resonance is observed at 1.4 eV binding energy. No surface states were observed above the valence-band maximum. Our results on the (111) surface show a strongly dispersing surface state that reaches its maximum 0.5 eV below the Fermi level at K. This result implies a gap of at least 0.5 eV in the surface electronic structure, which has consequences for the surface reconstruction in terms of a-bonded chain model. ͓S0163-1829͑97͒03416-4͔
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2002
Current knowledge of fine-particle airborne pollution concentrations and constituents with diamet... more Current knowledge of fine-particle airborne pollution concentrations and constituents with diameters below 2.5 µm (PM2.5) is limited. Sources are both natural and man-made. Here we describe two types of experiments performed using the Advanced Light Source (APS) facility at Chicago, and compare the results with PIXE analysis on the same fine particle filters. Firstly, broad beam (2 mm) studies with tuned synchrotron beam energies to help resolve overlapping X-rays and secondly highly focused X-ray beam studies (0.2µm) of individual fine particles from airborne pollution combustion sources.
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Papers by A. Stampfl