Twinning defects in spherical GeSi alloy nanocrystals

Yang, Yi; Wu, Xiaolan; Yang, Luwei; Kong, Fei

doi:10.1016/j.jcrysgro.2006.03.020

Cited by 15 publications

(16 citation statements)

References 19 publications

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“…More details pertaining to the sample preparation procedures can be found elsewhere. 16 X-ray diffraction results confirm that the two groups of samples containing NC-Ge 0.54 Si 0.46 and NC-Ge 0.28 Si 0.72 have a diamond structure embedded in a-SiO 2 matrix. Their morphologies and size distributions were characterized by high-resolution transmission electron microscopy ͑HRTEM͒ ͑JEOL-2010, equipped with energydispersive detection of the x ray emitted by an area of about ϫ 2 2 nm 2 of the sample͒.…”

Section: Samples and Experimentalsmentioning

confidence: 55%

“…Our recent work has shown that Ge x Si 1−x NCs of different sizes can be embedded in a-SiO 2 by Si-Ge-SiO 2 cosputtering and postprocessing. 16 This makes it possible to examine the different theoretical models and seek a global explanation for the frequencies and dampings of acoustic vibrations of the NCs embedded in the matrix. In this paper, we first show that two groups of NC-Ge x Si 1−x -embedded samples with different x both produce two polarized acoustic vibration modes in the lowfrequency Raman spectra.…”

Section: Introductionmentioning

confidence: 99%

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Nanocrystal-induced line narrowing of surface acoustic phonons in the Raman spectra of embeddedGexSi1−xalloy nanocrystals

Xiong

Yang

et al. 2008

Phys. Rev. B

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Raman scattering was performed on Ge x Si 1−x ͑x = 0.54 or 0.28͒ alloy nanocrystals embedded in amorphous Si oxide. An asymmetric, depolarized, and size-dependent low-frequency Raman peak was observed and identified as the superposition of two surface acoustic vibration modes of the alloy nanocrystals. The current theoretical models can be used to explain the mode frequencies but not the dampings observed experimentally. Based on energy-dispersive x-ray microanalysis and density-functional-theory total energy optimization of structures, a modified core-shell-matrix model in which the effects of neighboring nanocrystals in the matrix are taken into account is in good agreement with experiments. This work provides good insight into the frequencies and dampings of acoustic vibrations of the nanocrystals embedded in the matrix.

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Section: Samples and Experimentalsmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Nanocrystal-induced line narrowing of surface acoustic phonons in the Raman spectra of embeddedGexSi1−xalloy nanocrystals

Xiong

Yang

et al. 2008

Phys. Rev. B

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“…As a type of planar defects, twins have been frequently observed in transmission electron microscopy (TEM) analysis. 25,[31][32][33][34][35][36][37][38][39] However, the mechanism for the formation of twinned Si and Ge NCs has not been clear yet. Although different NC sizes should make a difference, Wang et al 25 claimed that it was twinning that attenuated the light emission from Si NCs.…”

Section: Introductionmentioning

confidence: 99%

Twinned silicon and germanium nanocrystals: Formation, stability and quantum confinement

et al. 2015

AIP Advances

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Although twins are often observed in Si/Ge nanocrystals (NCs), little theoretical investigation has been carried out to understand this type of important planar defects in Si/Ge NCs. We now study the twinning of Si/Ge NCs in the frame work of density functional theory by representatively considering single-twinned and fivefold-twinned Si/Ge NCs. It is found that the formation of twinned Si/Ge NCs is thermodynamically possible. The effect of twinning on the formation of Si NCs is different from that of Ge NCs. For both Si and Ge NCs twinning enhances their stability. The quantum confinement effect is weakened by twinning for Si NCs. Twinning actually enhances the quantum confinement of Ge NCs when they are small (<136 atoms), while weakening the quantum confinement of Ge NCs as their size is large (>136 atoms). The current results help to better understand the experimental work on twinned Si/Ge NCs and guide the tuning of Si/Ge-NC structures for desired properties.

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“…8 The bottom and top SiO 2 layers were deposited to protect the formed NCs. 8 The bottom and top SiO 2 layers were deposited to protect the formed NCs.…”

mentioning

confidence: 99%

“…The Ge and Si chips were placed on a large silica target and then cosputtered under 1 Pa Ar gas using 140 W power at room temperature. 8 With the aid of careful analysis of the HRTEM images acquired from a series of samples annealed at different conditions, the formation and disappearance mechanism of the twinning structure can be illustrated in Figs. The morphologies of the NCs were inspected by high-resolution transmission electron microscopy ͑HRTEM, FEI Titan 80-300 TEM͒.…”

mentioning

confidence: 99%