Raman study of nano‐crystalline Ge under high pressure

Abstract

We investigated high pressure behaviour of nano‐crystalline Ge that is free of substrate up to 17 GPa using Raman scattering. Nano‐crystalline Ge has been prepared by stain‐etching of 100 oriented Ge wafer and then lifted off. Electron diffraction measurements revealed that after etching particles retain diamond structure of original mono‐crystalline wafer. The Raman peak corresponding to zone‐center optical phonons mode was found to be shifted at ambient conditions from 300 cm–1 found in c‐Ge to around 280(1) cm–1 in nano‐crystalline Ge. Particle size was estimated from Raman and TEM measurements to be ∼5 nm. We observed no pressure transformation from the diamond to a high pressure phase as expected for bulk Ge (at around 10 GPa) in our Raman measurements. The pressure dependence of the Raman peak position was found to be highly nonlinear with dω /dP = 3.9(1) cm–1/GPa and d2ω /dP2 = –0.14(2) cm–1/GPa2. We discuss the microscopic origins of observed high pressure behavior of nano‐crystalline Ge. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Impact of Anchoring Monolayers on the Enhancement of Radiative Recombination in Light-Emitting Diodes Based on Silicon Nanocrystals

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Increased stability of nanocrystals of Gd2(Ti0.65Zr0.35)2O7 pyrochlore at high pressure

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“…However, the surface energy contribution becomes more important, or even dominant, as the grain-size decreases to very small values, because the ratio of the number of surface atoms to the total number of atoms goes from 10 −20 or less in bulk materials to values close to unity for small nanoclusters. Particularly for nano-sized materials, grain-size is another important factor that affects their structural stability and properties [11][12][13][14][15][16]. As an example, alumina, ␣-Al 2 O 3 (corundum) is the thermodynamically stable phase as a bulk sample, but nanosized crystals of Al 2 O 3 is often found in ␥-alumina form [17].…”

Growth and analysis of the tetragonal (ST12) germanium nanowires

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