Abstract
Unlike the complete solid solution of silicon–germanium, the temperature–composition phase diagram of neighbouring germanium–tin is characterised by virtually no bulk mutual solubility at ambient pressure. High pressures and temperatures, however, drastically change the electronic and structural characteristics of the liquid and solid states of these elements. This has recently been exploited to remove the ambient constraints leading to a novel tetragonal germanium–tin solid solution near 10 GPa. Scanning and field emission gun scanning electron microscopy as well as focused ion beam methods targeting specific regions of analysis of recovered products are employed, documenting here, crystallisation of germanium in a tin matrix below this pressure, reaction of germanium with tin near 10 GPa and formation of germanium–tin agglomerates above this pressure. We use these methodologies to prepare new silicon–germanium alloys as well.
Acknowledgements
Multianvil high-pressure experiments were performed at the Bayerisches Geoinstitut under the EU ‘Research Infrastructures: Transnational Access’ Programme (Contract No. 505320 (RITA) – High Pressure). A multianvil experiment was also performed in the Earth Science Department at the University of Bristol, and we warmly thank Alexandre Corgne and Bernard Wood for their generous assistance. We also thank Nicola Cayzer for much assistance with SEM measurements and Mike Hall for demanding solids processing. We also thank David Troadec, Niall Russell and Andrew McGaff for many discussions. We also acknowledge the use of the EPSRC Chemical Database Service at Daresbury.