Structural and chemical ordering of Heusler CoxMnyGez epitaxial films on Ge (111): Quantitative study using traditional and anomalous x-ray diffraction techniques
| Autor: | Yong S. Chu, Daniel Haskel, Liang He, Brian Collins, Frank Tsui |
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| Rok vydání: | 2015 |
| Předmět: | |
| Zdroj: | Physical Review B. 92 |
| ISSN: | 1550-235X 1098-0121 |
| Popis: | We found that epitaxial films of CoxMnyGez grown on Ge (111) substrates by molecular-beam-epitaxy techniques have been investigated as a continuous function of composition using combinatorial synchrotron x-ray diffraction (XRD) and x-ray fluorescence (XRF) spectroscopy techniques. A high-resolution ternary epitaxial phase diagram is obtained, revealing a small number of structural phases stabilized over large compositional regions. Ordering of the constituent elements in the compositional region near the full Heusler alloy Co2MnGe has been examined in detail using both traditional XRD and a new multiple-edge anomalous diffraction (MEAD) technique. Multiple-edge anomalous diffraction involves analyzing the energy dependence of multiple reflections across each constituent absorption edge in order to detect and quantify the elemental distribution of occupation in specific lattice sites. Results of this paper show that structural and chemical ordering are very sensitive to the Co : Mn atomic ratio, such that the ordering is the highest at an atomic ratio of 2 but significantly reduced even a few percent off this ratio. The in-plane lattice is nearly coherent with that of the Ge substrate, while the approximately 2% lattice mismatch is accommodated by the out-of-plane tetragonal strain. Furthermore, the quantitative MEAD analysis reveals no detectable amount ( |
| Databáze: | OpenAIRE |
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