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Université de Neuchâtel

X-ray absorption fine structure studies of buried Ge-Si interfaces

Aebi, Philipp ; Tyliszczak, T. ; Hitchcock, A. P. ; Jackman, T. E. ; Baribeau, J.-M.

In: Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 1991, vol. 9, no. 3, p. 907-911

We have used Ge A-edge x-ray absorption fine structure (EXAFS) and a gas ionization detector with sample rotation to study the local environment of nominally pure Qe layers buried in single crystal Si. The samples were grown by molecular-beam epitaxy on Si( 100). The dependence on thickness, number of Ge layers and growth temperature is explored. Considerable sensitivity to the quality of the...

Université de Neuchâtel

k-Space Mapping of Majority and Minority Bands on the Fermi Surface of Nickel below and above the Curie Temperature

Aebi, Philipp ; Kreutz, T. J. ; Osterwalder, J. ; Fasel, R. ; Schwaller, P. ; Schlapbach, Louis

In: Physical Review Letters, 1996, vol. 76, no. 7, p. 1150-1153

A section through the three-dimensional Fermi surface of Ni has been mapped perpendicular to the [110] direction using angle-scanned photoemission. Regions of minority and majority spin bands, well separated in k space, can clearly be identified through comparison with a band structure calculation. The behavior of the different bands is observed for temperatures below and above the Curie...

Université de Neuchâtel

Aebi et al. Reply

Aebi, Philipp ; Osterwalder, Jürg ; Schwaller, P. ; Schlapbach, Louis ; Shimoda, M. ; Mochiku, T. ; Kadowaki, K.

In: Physical Review Letters, 1995, vol. 74, no. 10, p. 1886

A Reply to the Comment by Sudip Chakravarty.

Université de Neuchâtel

Complete Fermi surface mapping of Bi2Sr2CaCu2O8+x(001): Coexistence of short range antiferromagnetic correlations and metallicity in the same phase

Aebi, Philipp ; Osterwalder, Jürg ; Schwaller, P. ; Schlapbach, Louis ; Shimoda, M. ; Mochiku, T. ; Kadowaki, K.

In: Physical Review Letters, 1994, vol. 72, no. 17, p. 2757-2760

The Fermi surface of Bi2Sr2CaCu2O8+x(001) has been mapped at nearly 6000 points in k space using angle-resolved photoemission at 300 K. We observe both features that are in good agreement with the local density calculation of Massidda, Yu, and Freeman [Physica (Amsterdam) 158C, 251 (1988)] and others that are missing in the calculation....

Université de Neuchâtel

Simultaneous analysis of multiple extended x-ray-absorption fine-structure spectra: Application to studies of buried Ge-Si interfaces

Aebi, Philipp ; Tyliszczak, T. ; Hitchcock, A. P. ; Baines, K. M. ; Sham, T. K. ; Jackman, T. E. ; Baribeau, J.-M. ; Lockwood, D. J.

In: Physical Review B, 1992, vol. 45, no. 23, p. 13579-13590

Ge K-edge extended x-ray-absorption fine-structure (EXAFS) spectra of a series of strained-layer [(Si)m/(Ge)n]p superlattices grown by molecular-beam epitaxy on the〈100〉face of single-crystal Si have provided a determination of the degree of intermixing and the extent of relaxation as a function of the thickness of the Ge layer. The...

Université de Neuchâtel

Nondipole channels in the electron-energy-loss structure near the 3s edge of copper

Aebi, Philipp ; Erbudak, M. ; Vanini, F. ; Vvedensky, D. D. ; Kostorz, G.

In: Physical Review B, 1992, vol. 42, no. 8, p. 5369-5372

Electronic transitions near the 3s edge of copper are investigated with electron-energy-loss spectroscopy and compared with real-space multiple-scattering calculations. Calculating the generalized oscillator strength illustrates the importance of dipole-forbidden transitions in the near-edge region and shows for the first time the feasibility of making detailed comparisons between theory...

Université de Neuchâtel

L and M edges of copper: Theory and experiment

Aebi, Philipp ; Erbudak, M. ; Vanini, F. ; Vvedensky, D. D. ; Kostorz, G.

In: Physical Review B, 1990, vol. 41, no. 17, p. 11760-11769

Characteristic electronic transitions and the associated fine structure in the near-edge region are investigated with electron-energy-loss spectroscopy for the copper L and M edges. In a single-particle scattering picture this fine structure represents the unoccupied density of states selected by the matrix elements. However, electronic processes can often complicate this simple...

Université de Neuchâtel

L2,3 edge of silicon: Theory and experiment

Aebi, Philipp ; Keller, J. ; Erbudak, M. ; Vanini, F.

In: Physical Review B, 1988, vol. 38, no. 8, p. 5392-5396

Structures in the electron-energy-loss spectrum up to 30 eV above the L2,3 edge of clean silicon, excited with high- and low-energy electrons, are found to be in good agreement with a multiple-scattering calculation of the empty density of states of a tetrahedral cluster of 17 silicon atoms. The relaxation of the excited atom is investigated by means of the emission...

Université de Neuchâtel

Angle-scanned photoemission: Fermi surface mapping and structural determination

Aebi, Philipp ; Fasel, Roman ; Naumovic, D. ; Hayoz, J. ; Pillo, Th. ; Bovet, M ; Agostino, R. G. ; Patthey, L. ; Schlapbach, Louis ; Gil, F. P. ; Berger, Helmuth ; Kreutz, T. J. ; Osterwalder, Jürg

In: Surface Science, 1998, vol. 402-404, p. 614-622

A brief survey of the angle-scanned photoemission technique is given. It incorporates two complementary methods in one: 1. Mapping of X-ray excited photoelectron intensities over virtually the complete hemisphere above the sample surface results in extended data sets where important surface-geometrical structure information is extracted and even “fingerprinting” is possible. This...

Université de Neuchâtel

On the search for Fermi surface nesting in quasi-2D materials

Aebi, Philipp ; Pillo, Th. ; Berger, Helmuth ; Lévy, F.

In: Journal of Electron Spectroscopy and Related Phenomena, 2001, vol. 117-118, p. 433-449

We investigate a number of isostructural, quasi-two dimensional transition metal dichalcogenides with respect to Fermi surface nesting. Using angle-resolved photoemission we find no clear evidence for Fermi surface nesting as a key scenario for charge density wave formation in these materials. However, interesting and unusual behavior has been discovered. For 1T-TaS2 in the...