Structure of crystalline and amorphous Ge probed by X-ray absorption and diffraction techniques

Results of experiments dedicated to the study of the structure under high pressure of amorphous Ge (a-Ge) and crystalline Ge (c-Ge) are reported. Energy-dispersive X-ray diffraction measurements of c-Ge have been collected at the DW11A beamline (DCI, LURE) using a heatable diamond anvil cell as pressure device up to 500 K. The a-Ge measurements have been performed at the ESRF, using the advanced set-up available at the BM29 beamline, which allows the simultaneous collection of X-ray absorption spectroscopy data and diffraction patterns used to monitor pressure and crystallization of a sample in a Paris-Edinburgh large-volume cell. The new structural data allowed us to obtain a reliable determination of the lattice parameters as a function of pressure and temperature in c-Ge and of the first-neighbor distance distribution in a-Ge.