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1. LEED Holography applied to a complex superstructure: a direct view of the adatom cluster on SiC(111)-(3x3)

Author

Reuter, K., Schardt, J., Bernhardt, J., Wedler, H., Starke, U., and Heinz, K.

Subjects
Condensed Matter - Materials Science
Abstract

For the example of the SiC(111)-(3x3) reconstruction we show that a holographic interpretation of discrete Low Energy Electron Diffraction (LEED) spot intensities arising from ordered, large unit cell superstructures can give direct access to the local geometry of a cluster around an elevated atom, provided there is only one such prominent atom per surface unit cell. By comparing the holographic images obtained from experimental and calculated data we illuminate validity, current limits and possible shortcomings of the method. In particular, we show that periodic vacancies such as cornerholes may inhibit the correct detection of the atomic positions. By contrast, the extra diffraction intensity due to slight substrate reconstructions, as for example buckling, seems to have negligible influence on the images. Due to the spatial information depth of the method the stacking of the cluster can be imaged down to the fourth layer. Finally, it is demonstrated how this structural knowledge of the adcluster geometry can be used to guide the dynamical intensity analysis subsequent to the holographic reconstruction and necessary to retrieve the full unit cell structure., Comment: 11 pages RevTex, 6 figures, Phys. Rev. B in press

Published
1998
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3. Performance of Rooftop PV Systems in Selected European Countries from 2012 to 2019

Author

Schardt, J. and Te Heesen, H.

Subjects
Operation, Performance and Maintenance of PV Systems, PV Systems and Storage – Modelling, Design, Operation and Performance
Abstract

37th European Photovoltaic Solar Energy Conference and Exhibition; 1409-1412, The electrical energy generated by solar photovoltaic (PV) contributes significantly to the transition to green energy production. A comprehensive analysis of PV systems' yield data and performance is necessary to plan future energy production by solar photovoltaics. This publication evaluates publicly available yield data, configuration, and location of 32,744 rooftop PV systems in Europe. The analyzed period ranges from 2012 to 2019 and has a time resolution of one day. The considered PV systems are installed in the Netherlands, Belgium, Luxembourg, Germany, France, and Italy. The evaluation focuses on the long-term specific yield and performance ratio analysis. The specific yield over the whole area shows the expected south-north gradient. The long-term average specific yields and performance ratio of systems that ran continuously from 2015 to 2019 were 947 kWh/kWp and 0.73 in the Netherlands, 959 kWh/kWp and 0.73 in Belgium, 979 kWh/kWp and 0.73 in Luxembourg, 990 kWh/kWp and 0.74 in Germany, 1102 kWh/kWp and 0.73 in France, and 1195 kWh/kWp and 0.73 in Italy. The average performance ratio of PV systems operated for five consecutive years from 2015 to 2019 shows no correlation with system capacity. The performance trend of PV systems installed after 2008 does not increase.

Published
2020
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8. Differentialdiagnose des pulmonalen Infiltrates nach Pneumothorax-Drainage

Author

Hoksch, B., Weber, T., Beshay, M., Stein, R., Schardt, J., Schmid, R., Hoksch, B., Weber, T., Beshay, M., Stein, R., Schardt, J., and Schmid, R.

Abstract

Zusammenfassung: Das Reexpansionsödem der Lunge stellt insgesamt eine seltene Komplikation sowohl im Rahmen der Pneumothoraxtherapie als auch bei der Behandlung des ausgedehnten Pleuraergusses dar. Die Pathogenese ist nicht vollständig geklärt und scheint multifaktoriell zu sein. Bei Auftreten von Atembeschwerden nach Reexpansion einer zuvor kollabierten Lunge sollte unbedingt an ein Reexpansionsödem als mögliche Ursache gedacht werden

Published
2018

13. Novel Reconstruction Mechanism for Dangling-Bond Minimization: Combined Method Surface Structure Determination of SiC(111)-(3×3)

Author

Starke, U., Schardt, J., Bernhardt, J., Franke, M., Reuter, K., Wedler, H., Heinz, K., Furthmüller, J., Käckell, P., and Bechstedt, F.

Abstract

The SiC(111)−(3×3) phase was analyzed by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED) holography, density functional theory (DFT), and conventional LEED. A single adatom per unit cell found in STM acts as a beam splitter for the holographic inversion of discrete LEED spot intensities. The resulting 3D image guides the detailed analyses by LEED and DFT which find a Si tetramer on a twisted Si adlayer with cloverlike rings. This twist model with one dangling bond left per unit cell represents a novel (n×n)-reconstruction mechanism of group-IV (111) surfaces.

Published
1998

43. Structure of Epitaxial CoSi2 Films on Si(111) Studied with Low-Energy Electron Diffraction (LEED).

Author

Starke, U., Schardt, J., Weiß, W., Rangelov, G., Fauster, Th., and Heinz, K.

Abstract

Expitaxial films of 2 on Si(111) were investigated by low-energy electron diffraction. Films of approximately 12 Å thickness were prepared by simultaneous deposition of Co and Si and subsequent annealing. The films were found to crystallize in 2 structure in (111) orientation. Two (1×1) phases of different stoichiometry exist. The surface phase that contains more Co is found to be a 2(111) bulklike structure terminated by a Si-Co-Si trilayer. The Si-rich phase is terminated by an additional nonrotated silicon bilayer with the lower silicon atoms bound to cobalt in the first 2 layer. Consequently, these cobalt atoms have an eightfold coordination. Due to the lattice mismatch the silicide films are expanded by 0.5% in the lateral direction and contracted by 1.4% in the vertical direction. [ABSTRACT FROM AUTHOR]

Published
1998
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46. Differentialdiagnose des pulmonalen Infiltrates nach Pneumothorax-Drainage

Author

Hoksch, B., Weber, T., Beshay, M., Stein, R., Schardt, J., Schmid, R., Hoksch, B., Weber, T., Beshay, M., Stein, R., Schardt, J., and Schmid, R.

Abstract

Zusammenfassung: Das Reexpansionsödem der Lunge stellt insgesamt eine seltene Komplikation sowohl im Rahmen der Pneumothoraxtherapie als auch bei der Behandlung des ausgedehnten Pleuraergusses dar. Die Pathogenese ist nicht vollständig geklärt und scheint multifaktoriell zu sein. Bei Auftreten von Atembeschwerden nach Reexpansion einer zuvor kollabierten Lunge sollte unbedingt an ein Reexpansionsödem als mögliche Ursache gedacht werden

47. Interface structure of ultrathin CoSi[sub 2] films epitaxially grown on Si(111).

Author

Seubert, A., Schardt, J., Weiß, W., Starke, U., Heinz, K., and Fauster, Th.

Subjects
*INTERFACES (Physical sciences), *THIN films, *ELECTRON diffraction, *SILICON
Abstract

The interface structure of ultrathin CoSi[sub 2] films grown on Si(111) was investigated by quantitative low-energy electron diffraction. Codeposition of the elements leads to a film composed of domains with two and three Si-Co-Si trilayers in CaF[sub 2] structure. As within the film, Co atoms at the interface are eightfold coordinated. The lateral unit cells of the film and substrate are mutually rotated by 60° (B-type orientation). The interfacial trilayer is substantially distorted, its distance to the substrate expanded, and its sublayer spacings considerably modified from the bulk. Also, the substrate's top spacing is expanded. The results compare almost quantitatively with recent density-functional calculations. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2000
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