"A long-standing goal of physicists, chemists, and materials scientists is to have a perfect phase diagram of a material. EFree researchers Xiao-Jia Chen, Yue Meng, Viktor Struzhkin, and Ho-Kwang (Dave) Mao, along with collaborators from China, reported on delicate experiments designed to obtain a complete high-pressure phase diagram of the compressed Ge. Their results show extraordinary agreement between theory and experiment in terms of the way germanium behaves under pressure.
Research predicts Germanium's pressure-dependent superconductivity up to 190 GPa, which helps classification of Ge as a standard electron-phonon coupling superconductor. The research article, published by Physical Review Letters, reported that under pressure of 66 GPa, germanium undergoes a structural change from the metallic white tin structure to an orthorhombic Imma structure. It then undergoes another change under pressure of 90 GPa to the simple hexagonal structure. These findings matched with theoretical predictions about the element’s behavior under extreme pressure.
Ge is an important element for semiconductor industry and has many advantages over Si due to its higher intrinsic electron mobilities, higher intrinsic carrier concentrations; larger bulk excitonic Bohr radii, enabling integration with current semiconductor processing technology. Ge’s compatibility with group III-IV materials (e.g. good lattice matching with GaAs) and germanium oxide’s optical properties allow radial integrated optoelectronic circuitry designs. Ge is an ideal material for experimental and theoretical studies due to the crystal structure change of Ge at high pressures from the semiconducting diamond-type structure to high-symmetry structures of increasing coordination.
This research was supported by the Department of Energy in the United States and by the HKRGS and NSFC in China.
See: Xiao-Jia Chen, Chao Zhang, Yue Meng, Rui-Qin Zhang, Hai-Qing Lin, Viktor V. Struzhkin, Ho-kwang Mao, b-tin--imma--sh Phase Transitions of Germanium”, Phys. Rev. Lett. 106, 135502 (2011). (pub. 30 March 2011). News is also at Carnegie Institution’s website.
Image: Atomic arrangement of the β-tin (a), Imma (b), and sh (c) structures of Ge."
https://efree.gl.ciw.edu/content/%E2%80 ... -germanium
