Germanium-silicon alloy and core–shell nanocrystals by gas phase synthesis

Mehringer, Christian; Kloner, Christian; Butz, Benjamin; Winter, Benjamin; Spiecker, Erdmann; Peukert, Wolfgang

doi:10.1039/c4nr06318j

Cited by 19 publications

(17 citation statements)

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“…Such core shell structure was not observed previously in SiGe particles, even when the laser pyrolysis method was employed . The peculiar morphologies we obtained may originate from distinct experimental conditions.…”

Section: Resultssupporting

confidence: 44%

Best Performing SiGe/Si Core‐Shell Nanoparticles Synthesized in One Step for High Capacity Anodes

Desrues

Alper

Boismain

et al. 2019

Batteries & Supercaps

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Silicon-germanium nanostructures are promising anode materials for high stability, high capacity, and fast cycling Li-ion batteries. In this work, we report on the outstanding performance of new SiGe/Si core@shell nanoparticle heterostructures synthetized in one step by laser pyrolysis of silane and germane. By tuning the silane to germane ratio, the composition of Si 100-x Ge x alloy was readily adjusted. Nanoparticles with x = 0, 20, 47, 77, and 100 were investigated and the composition of each alloy (including internal mixed phases) was confirmed by X-ray diffraction and energy-dispersive X-ray spectroscopy. The electrochemical performances of the Si 100-x Ge x alloys were evaluated by cycling half cell batteries from C/5 to 5 C. The optimal trade-off between stability and capacity was obtained in Si 53 Ge 47 core shell nanoparticles alloy. This material exhibits the best performance reported so far for SiGe compounds, with a reversible specific capacity of 1695 mAh.g À 1 after 60 cycles (90 % of its initial value). The (de)alloying properties of this optimal Si 53 Ge 47 heterostructure were followed by operando synchrotron WAXS measurements, suggesting sequential lithiation of the various phases present in the material. The alloying process, combined with the realization of peculiar nanostructures composed of a Ge-rich core and a Sirich shell, therefore allow to reach electrochemical properties suited for a practical application in energy storage device.

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Section: Resultssupporting

confidence: 44%

Best Performing SiGe/Si Core‐Shell Nanoparticles Synthesized in One Step for High Capacity Anodes

Desrues

Alper

Boismain

et al. 2019

Batteries & Supercaps

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“…The devices based on SiGe represent one of the most promising candidates and would be a breakthrough that will open possibilities for the new system-on-a-chip to incorporate optoelectronic devices into Si electronics. This can be implemented if we consider SiGe alloy advantages like tunable bandgap 11,12 and tunable lattice constant 2 by controlling the Ge fraction in the alloy leading to lower annealing temperature, relative low cost, flexibility of technological processing, and overcoming different electronic compatibility reasons 13 . The scientific effort is spent to understand the conditions of SiGe NCs formation into dielectric matrices (e.g.…”

mentioning

confidence: 99%

SiGe nanocrystals in SiO2 with high photosensitivity from visible to short-wave infrared

Stavarache

Logofatu

Sultan

et al. 2020

Sci Rep

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Films of SiGe nanocrystals (NCs) in oxide have the advantage of tuning the energy band gap by adjusting SiGe NCs composition and size. In this study, SiGe-SiO2 amorphous films were deposited by magnetron sputtering on Si substrate followed by rapid thermal annealing at 700, 800 and 1000 °C. We investigated films with Si:Ge:SiO2 compositions of 25:25:50 vol.% and 5:45:50 vol.%. TEM investigations reveal the major changes in films morphology (SiGe NCs with different sizes and densities) produced by Si:Ge ratio and annealing temperature. XPS also show that the film depth profile of SiGe content is dependent on the annealing temperature. These changes strongly influence electrical and photoconduction properties. Depending on annealing temperature and Si:Ge ratio, photocurrents can be 103 times higher than dark currents. The photocurrent cutoff wavelength obtained on samples with 25:25 vol% SiGe ratio decreases with annealing temperature increase from 1260 nm in SWIR for 700 °C annealed films to 1210 nm for those at 1000 °C. By increasing Ge content in SiGe (5:45 vol%) the cutoff wavelength significantly shifts to 1345 nm (800 °C annealing). By performing measurements at 100 K, the cutoff wavelength extends in SWIR to 1630 nm having high photoresponsivity of 9.35 AW−1.

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“…In past, various techniques were used, such as mechanical alloying by ball milling, 26 wet chemical etching 27 and molecular beam epitaxy, [28][29][30] wet chemical synthesis 31,32 , synthesis from gas phase (silane and germane) [33][34][35][36] and cosputtering. [37][38][39] The segregation of Ge and Si is often the case for Ge-rich SiGe alloys, even though miscibility of Ge and Si is expected for whole compositional range.…”

Section: Introductionmentioning

confidence: 99%

Tuning Optical Properties of Ge Nanocrystals by Si Shell

et al. 2016

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We present a theoretical study of Ge-core/Si-shell nanocrystals in a wide bandgap matrix and compare the results with experimental data obtained from the samples prepared by co-sputtering. The empirical tight-binding technique allows us to account for the electronic structure under strain on the atomistic level. We find that a Si shell as thick as 1 monolayer is enough to reduce the radiative recombination rate as a result of valley L − X cross-over. Thin Si shell leads to a dramatic reduction of the optical bandgap from visible to near-infrared range, which is promising for photovoltaics and photodetector applications.Our detailed analysis of the structure of the confined electron and hole states in real and reciprocal spaces indicates that the type-II heterostructure is not yet achieved for Si shells with the thickness below 0.8 nm, despite some earlier theoretical predictions. The energy levels of holes are affected by the Si shell stronger than the electron states, even though holes are completely confined to the Ge core. This occurs probably due to a strong influence of strain on the band offsets.

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Germanium-silicon alloy and core–shell nanocrystals by gas phase synthesis

Cited by 19 publications

References 50 publications

Best Performing SiGe/Si Core‐Shell Nanoparticles Synthesized in One Step for High Capacity Anodes

Best Performing SiGe/Si Core‐Shell Nanoparticles Synthesized in One Step for High Capacity Anodes

SiGe nanocrystals in SiO2 with high photosensitivity from visible to short-wave infrared

Tuning Optical Properties of Ge Nanocrystals by Si Shell

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