Abstract
Amorphous germanium (a-Ge) structure is known to show a complex behavior upon pressurization. Here an XAS experiment on a-Ge at high pressure and temperature is presented, which is aimed to investigate such behavior and verify the presence of polyamorphism. High quality a-Ge EXAFS spectra (Ge K-edge) have been collected up to 8.3 GPa. The data analysis, realized using the GNXAS package, gives precise values of the first neighbor bond lengths at various pressures. Two well defined behaviors of the a-Ge local atomic structure have been observed, depending on the sample temperature. At 475 K a-Ge starts to crystallize above 8 GPa. On the other hand, at room temperature, the data seem to indicate the occurrence of a transition toward a different amorphous structure, well before the start of the process of crystallization.
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