Pressure-induced amorphisation and a new high density amorphous metallic phase in matrix-free Ge nanoparticles

Over the last two decades it has been demonstrated that size effects have significant consequences for the atomic arrangements and phase behaviour of matter under extreme pressure. Furthermore, it has been shown that understanding of how size affects critical pressure-temperature conditions provides vital guidance in the search for materials with novel properties. Here we report on the remarkable behaviour in small (under $\sim$ 5 nm) matrix-free Ge nanoparticles under hydrostatic compression that is drastically different from both larger nanoparticles and bulk Ge. We discover that the application of pressure drives surface-induced amorphisation leading to Ge–Ge bond over-compression and eventually to a polyamorphic semiconductor-to-metal transformation. A combination of spectroscopic techniques together with \textit{ab initio} simulations were employed to reveal the details of the transformation mechanism into a new high density phase—amorphous metallic Ge.

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acs.nanolett.5b02627
Categories: Original research papers, Research