High Pressure in situ Micro-Raman Spectroscopy of Ge-Sn System Synthesized in a Laser Heated Diamond Anvil Cell.

GexSn1-x has been predicted to be a direct band-gap semiconductor, but attempts to synthesize this in bulk form by conventional synthesis methods have not been successful on account of the poor solubility of Sn in Ge. In this work, laser heated diamond anvil cell (LHDAC) technique has been employed to explore formation of bulk GexSn1-x (x = 0.7) at varying pressures and temperatures. At ∼8 GPa, in situ micro-Raman spectroscopy done on several regions of temperature quenched samples laser heated up to ∼2000 K reveals vanishing of the intense Ge TO(Γ) phonon at ∼326 cm-1 and appearance of a softer mode, concurrent with appearance of a new high intensity Raman mode at ∼660 cm-1. These indicate dilation of the Ge-Ge bond by virtue of significant miscibility of βSn at these high P-T conditions and hints at formation of new stiff Ge-Sn bonds. [ABSTRACT FROM AUTHOR]