New metastable phases of silicon

Zhao, You-Xiang; Buehler, Fred; Sites, James R.; Spain, Ian L.

doi:10.1016/0038-1098(86)90372-8

Cited by 148 publications

(98 citation statements)

References 16 publications

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“…Other polymorph phases where reported from heat treatment of Si-III and in high pressure test experiments. They were labeled as Si-IV [13,29] and Si-IX [30], and because they were not detected, they are not studied in the current work. Figure 4 shows the micro-Raman spectra obtained from the 2 µm/s nanoscratch presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

Deformation mechanisms of silicon during nanoscratching

Gassilloud

Ballif

Gasser

et al. 2005

Physica Status Solidi (a)

110

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Dedicated to Professor Horst P. Strunk on the occasion of his 65th birthday PACS 62.20Fe, 61.50Ks, 61.43Dq, 63.20Mt, 61.72Ff, 68.37Hk The deformation mechanisms of silicon {001} surfaces during nanoscratching were found to depend strongly on the loading conditions. Nanoscratches with increasing load were performed at 2 µm/s (low velocity) and 100 µm/s (high velocity). The load-penetration-distance curves acquired during the scratching process at low velocity suggests that two deformation regimes can be defined, an elasto-plastic regime at low loads and a fully plastic regime at high loads. High resolution scanning electron microscopy of the damaged location shows that the residual scratch morphologies are strongly influenced by the scratch velocity and the applied load. Micro-Raman spectroscopy shows that after pressure release, the deformed volume inside the nanoscratch is mainly composed of amorphous silicon and Si-XII at low scratch speeds and of amorphous silicon at high speeds. Transmission electron microscopy shows that Si nanocrystals are embedded in an amorphous matrix at low speeds, whereas at high speeds the transformed zone is completely amorphous. Furthermore, the extend of the transformed zone is almost independent of the scratching speed and is delimited by a dislocation rich area that extends about as deep as the contact radius into the surface. To explain the observed phase and defect distribution a contact mechanics based decompression model that takes into account the load, the velocity, the materials properties and the contact radius in scratching is proposed. It shows that the decompression rate is higher at low penetration depth, which is consistent with the observation of amorphous silicon in this case. The stress field under the tip is computed using an elastic contact mechanics model based on Hertz's theory. The model explains the observed shape of the transformed zone and suggests that during load increase, phase transformation takes place prior to dislocation nucleation.

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Section: Resultsmentioning

confidence: 99%

Deformation mechanisms of silicon during nanoscratching

Gassilloud

Ballif

Gasser

et al. 2005

Physica Status Solidi (a)

110

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“…The experimental values for the transition pressures vary between 103 and 133 kbar for Si 1,2,3,4,5,6,7 and between 103 and 110 kbar for Ge 5,6,7,8,9,10,11 where the firmed values are at around 110 kbar and 105 kbar, respectively. In both cases, our results obtained with GGA agree perfectly, whereas the LDA result underestimates the experimental value, which is a well known problem.…”

Section: Discussion Of the Resultsmentioning

confidence: 99%

Transition pressures and enthalpy barriers for the cubic diamond→β-tin transition in Si and Ge under nonhydrostatic conditions

Gaál-Nagy

Strauch

2006

Phys. Rev. B

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We present an ab-initio study of the phase transition cd→β-tin in Si and Ge under hydrostatic and non-hydrostatic pressure. For this purpose we have developed a new method to calculate the influence of non-hydrostatic pressure components not only on the transition pressure but also on the enthalpy barriers between the phases. We find good agreement with available experimental and other theoretical data. The calculations have been performed using the plane-wave pseudopotential approach to the density-functional theory within the local-density and the generalized-gradient approximation implemented in VASP.

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“…A recent metadynamics simulation by employing a high dimensional neural network potential has successfully reproduced this sequence [27]. However, the above transitions are not fully reversible upon decompression [28,29]. The Si-II phase transforms to an exotic semimetallic phase R8 (Si-XII) at 9.3 GPa, and further to another metastable cubic form BC8 (Si-III) that persists until ambient conditions.…”

Section: Decompression On Si-iimentioning

confidence: 98%

Generalized evolutionary metadynamics for sampling the energy landscapes and its applications

et al. 2015

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We present an automated scheme to systematically sample energy landscapes of crystalline solids, based on the ideas of metadynamics and evolutionary algorithms. Phase transitions are driven by the evolution of the order parameter (in this case, 6-dimensional cell vectors) and aided by atomic displacements corresponding to both zero and non-zero wave vectors, enabling cell size to spontaneously change during simulation. Our technique can be used for efficient prediction of stable crystal structures, and is particularly powerful for mining numerous low-energy configurations and phase transition pathways. By applying this method to boron, we find numerous energetically competitive configurations, based on various packings of B12 icosahedra. We also observed a low-energy metastable structure of Si(T32) which is likely to be a product of decompression on Si-II. T32 is calculated to have a quasidirect band gap of 1.28 eV, making it promising for photovoltaic applications.

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New metastable phases of silicon

Cited by 148 publications

References 16 publications

Deformation mechanisms of silicon during nanoscratching

Deformation mechanisms of silicon during nanoscratching

Transition pressures and enthalpy barriers for the cubic diamond→β-tin transition in Si and Ge under nonhydrostatic conditions

Generalized evolutionary metadynamics for sampling the energy landscapes and its applications

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