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Your search keyword '"Crozier, E. D."' showing total 131 results
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131 results on '"Crozier, E. D."'

1. Instability of the topological surface state in Bi$_2$Se$_3$ upon deposition of gold

Author

Polyakov, A., Tusche, C., Ellguth, M., Crozier, E. D., Mohseni, K., Otrokov, M. M., Zubizarreta, X., Vergniory, M. G., Geilhufe, M., Chulkov, E. V., Ernst, A., Meyerheim, H. L., and Parkin, S. S. P.

Subjects
Condensed Matter - Materials Science
Abstract

Momentum resolved photoemission spectroscopy indicates the instability of the Dirac surface state upon deposition of gold on the (0001) surface of the topological insulator Bi$_2$Se$_3$. Based on the structure model derived from extended x-ray absorption fine structure experiments showing that gold atoms substitute bismuth atoms, first principles calculations provide evidence that a gap appears due to hybridization of the surface state with gold d-states near the Fermi level. Our findings provide new insights into the mechanisms affecting the stability of the surface state., Comment: 6 pages, 4 figures

Published
2018
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2. Surfactant mediated growth of ferromagnetic Mn {\delta}-doped Si

Author

Kahwaji, S., Gordon, R. A., Crozier, E. D., Roorda, S., Robertson, M. D., Zhu, J., and Monchesky, T. L.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We present an investigation of Mn {\delta}-doped layers in Si(001) grown by molecular beam epitaxy. We discovered that a Pb surfactant has significant effect on the structural and magnetic properties of the submonolayer of Mn, which depends on the Si capping layer growth temperature, T_Si, and the Mn coverage, {\theta}_Mn. The results presented in this paper identify three regions in the growth-phase-diagram characterized by distinct magnetic behaviors and crystal structures. In one region, X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM) experiments indicate that MnSi nanocrystallites form with B2-like crystal type structures. At the optimal growth conditions, T_Si = 200 C and {\theta}_Mn = 0.26 monolayer, a ferromagnetic phase develops with a Curie temperature T_C > 400 K and a saturation moment m_sat = 1.56 {\mu}_B/Mn, whereas T_C drops to zero for a control sample prepared without Pb. For T_Si > 200 C, MnSi-B20 type precipitates form with a T_C ~ 170 K. Rutherford backscattering spectroscopy shows that the increase in the remanent magnetization in these two phases is possibly correlated with an increase in the Mn substitutional fraction, which suggests that a Si_{1-x}Mn_x dilute magnetic semiconductor may be forming in the matrix between the precipitates. Density functional calculations show that Pb changes the pathway by which the Mn atoms access the Si substitutional sites, Mn_Si. While the Pb increases the formation energy of Mn_Si at the Si surface, it enables substitutional incorporation by lowering the formation energy of Si vacancies by 0.92 eV., Comment: 10 pages, 8 figures

Published
2013
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3. Local environment of Nitrogen in GaN{y}As{1-y} epilayers on GaAs (001) studied using X-ray absorption near edge spectroscopy

Author

Gupta, J. A., Dharma-wardana, M. W. C., Jürgensen, A., Crozier, E. D., Rehr, J. J., and Prange, M.

Subjects
Condensed Matter - Materials Science
Abstract

X-ray absorption near-edge spectroscopy (XANES) is used to study the N environment in bulk GaN and in GaN{y}As{1-y} epilayers on GaAs (001), for y \~5%. Density-functional optimized structures were used to predict XANES via multiple-scattering theory. We obtain striking agreement for pure GaN. An alloy model with nitrogen pairs on Ga accurately predicts the threshold energy, the width of the XANES ``white line'', and features above threshold, for the given X-ray polarization. The presence of N-pairs may point to a role for molecular N_2 in epitaxial growth kinetics., Comment: Four pages (PRL style) with two figures

Published
2004
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4. Reply to “Comment on ‘Instability of the topological surface state in Bi2Se3 upon deposition of gold' ”

Author

Polyakov, A., primary, Tusche, C., additional, Ellguth, M., additional, Crozier, E. D., additional, Mohseni, K., additional, Otrokov, M. M., additional, Zubizarreta, X., additional, Vergniory, M. G., additional, Geilhufe, M., additional, Chulkov, E. V., additional, Ernst, A., additional, Meyerheim, H. L., additional, and Parkin, S. S. P., additional

Published
2018
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9. Instability of the topological surface state in Bi2Se3 upon deposition of gold

Author

Polyakov, A., primary, Tusche, C., additional, Ellguth, M., additional, Crozier, E. D., additional, Mohseni, K., additional, Otrokov, M. M., additional, Zubizarreta, X., additional, Vergniory, M. G., additional, Geilhufe, M., additional, Chulkov, E. V., additional, Ernst, A., additional, Meyerheim, H. L., additional, and Parkin, S. S. P., additional

Published
2017
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12. XANES at High-Pressure Phase Transitions

Author

Ingalls, R., Tranquada, J. M., Whitmore, J. E., Crozier, E. D., Goldanskii, Vitalii I., editor, Gomer, Robert, editor, Schäfer, Fritz Peter, editor, Toennies, J. Peter, editor, Bianconi, Antonio, editor, Incoccia, Lucia, editor, and Stipcich, Stanislao, editor

Published
1983
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16. Surfactant mediated growth of ferromagnetic Mn ��-doped Si

Author

Kahwaji, S., Gordon, R. A., Crozier, E. D., Roorda, S., Robertson, M. D., Zhu, J., and Monchesky, T. L.

Subjects
Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences
Abstract

We present an investigation of Mn ��-doped layers in Si(001) grown by molecular beam epitaxy. We discovered that a Pb surfactant has significant effect on the structural and magnetic properties of the submonolayer of Mn, which depends on the Si capping layer growth temperature, T_Si, and the Mn coverage, ��_Mn. The results presented in this paper identify three regions in the growth-phase-diagram characterized by distinct magnetic behaviors and crystal structures. In one region, X-ray absorption fine structure (XAFS) and transmission electron microscopy (TEM) experiments indicate that MnSi nanocrystallites form with B2-like crystal type structures. At the optimal growth conditions, T_Si = 200 C and ��_Mn = 0.26 monolayer, a ferromagnetic phase develops with a Curie temperature T_C > 400 K and a saturation moment m_sat = 1.56 ��_B/Mn, whereas T_C drops to zero for a control sample prepared without Pb. For T_Si > 200 C, MnSi-B20 type precipitates form with a T_C ~ 170 K. Rutherford backscattering spectroscopy shows that the increase in the remanent magnetization in these two phases is possibly correlated with an increase in the Mn substitutional fraction, which suggests that a Si_{1-x}Mn_x dilute magnetic semiconductor may be forming in the matrix between the precipitates. Density functional calculations show that Pb changes the pathway by which the Mn atoms access the Si substitutional sites, Mn_Si. While the Pb increases the formation energy of Mn_Si at the Si surface, it enables substitutional incorporation by lowering the formation energy of Si vacancies by 0.92 eV., 10 pages, 8 figures

Published
2013
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22. Coordination of Fe, Ga and Ge in high pressure glasses by Moessbauer, Raman and X-ray absorption spectroscopy, and geological implications

Author

Fleet, M. E, Henderson, G. S, Herzberg, C. T, Crozier, E. D, Osborne, M. D, and Scarfe, C. M

Subjects
Geophysics
Abstract

For some time, it has been recognized that the structure of silicate liquids has a great bearing on such magma properties as viscosity, diffusivity, and thermal expansion and on the extrapolation of thermodynamic quantities outside of the experimentally measurable range. In this connection it is vital to know if pressure imposes changes in melt structure similar to the pressure-induced reconstructive transformations in crystals. In the present study on 1 bar and high pressure glasses, an investigation is conducted regarding the coordination of Fe(3+) in Fe silicate glasses by Moessbauer spectroscopy. Raman spectroscopy is employed to explore the coordinations of Ge(4+) in GeO2 glasses and of Ga(3+) in NaGa silicate glasses, while the coordination of Ga(3+) in NaGaSiO4 glasses is studied with the aid of methods of X-ray absorption spectroscopy.

Published
1984
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34. XAFS and micro-XAFS at the PNC-CAT beamlines

Author

Heald, S. M., primary, Brewe, D. L., additional, Stern, E. A., additional, Kim, K. H., additional, Brown, F. C., additional, Jiang, D. T., additional, Crozier, E. D., additional, and Gordon, R. A., additional

Published
1999
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40. Prospects for using high-power x rays as a volumetric heat source

Author

Rosenberg, Richard A., primary, Farrell, William, additional, Ma, Qing, additional, Mancini, Derrick C., additional, Khounsary, Ali M., additional, Sheng, I. C. A., additional, Crozier, E. D., additional, Soerensen, Georg J., additional, Gordon, Robert A., additional, and Jiang, De-Tong, additional

Published
1997
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