Formation of Ge nanocrystals in amorphous GeO x , and SiGeO x alloy films

Zacharias, Mario; Bläsing, J.; Löhmann, M.; Christen, J.

doi:10.1016/0040-6090(95)08133-x

Cited by 23 publications

(14 citation statements)

References 14 publications

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“…65–8052 and 65–0333, respectively). This demonstrates that the germanium oxide species in the composite was GeO x where x < 2 instead of pure GeO 2 or Ge, with the value of x determined as described below . The presence of the Ge–O bond in GeO x was further proved by Fourier transform infrared spectroscopy (FTIR).…”

Section: Resultsmentioning

confidence: 92%

“…As shown in Figure a, the composite exhibits an amorphous structure, with only one broad diffraction peak observed at 2 θ of 20–35°. The characteristic broad peak is ascribed to the diffraction of short‐range ordered Ge–O crystalline structure in amorphous GeO x , and indicates the nanosized particles of the materials. If heated at 600 °C under Ar, the GeO x in the composite disproportionates and phase separates into crystalline GeO 2 and Ge (Figure S1b, Supporting Information), as confirmed by comparison with the standard XRD patterns shown in Figure S1c,d (Supporting Information, JCPDS no.…”

Section: Resultsmentioning

confidence: 99%

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GeO_x/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li₂O along with Improved Rate Performance

Gordin

et al. 2013

Adv Funct Materials

146

143

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A self-assembled GeO x /reduced graphene oxide (GeO x /RGO) composite, where GeO x nanoparticles are grown directly on reduced graphene oxide sheets, is synthesized via a facile one-step reduction approach and studied by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy elemental mapping, and other techniques. Electrochemical evaluation indicates that incorporation of reduced graphene oxide enhances both the rate capability and reversible capacity of GeO x , with the latter being due to the RGO enabling reversible utilization of Li 2 O. The composite delivers a high reversible capacity of 1600 mAh g −1 at a current density of 100 mA g −1 , and still maintains a capacity of 410 mAh g −1 at a high current density of 20 A g −1 . Owing to the fl exible reduced graphene oxide sheets enwrapping the GeO x particles, the cycling stability of the composite is also improved signifi cantly. To further demonstrate its feasibility in practical applications, the synthesized GeO x /RGO composite anode is successfully paired with a high voltage LiNi 0.5 Mn 1.5 O 4 cathode to form a full cell, which shows good cycling and rate performance.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

GeO_x/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li₂O along with Improved Rate Performance

Gordin

et al. 2013

Adv Funct Materials

146

143

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“…Luminescent Ge nanocrystals ͑nc-Ge͒ have been fabricated by several groups using rf cosputtering, ion implantation, dc sputtering in a reactive oxygen environment or oxidation of SiGe alloys, and subsequent thermal annealing to induce the crystallization. [1][2][3][4][5] The usual photoluminescence ͑PL͒ spectrum is a broad band centered at 2.1-2.4 eV, 2,6 although another band near 1.83 eV has also been reported. 3 However, there is no clear evidence for a size dependent blue shift of the PL peak, as expected from carrier quantum confinement in quantum dots.…”

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confidence: 99%

Blue luminescence in films containing Ge and GeO2 nanocrystals: The role of defects

Zacharias

Fauchet

1997

Applied Physics Letters

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254

196

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X-ray measurements show that GeO2 and Ge nanocrystals with a radius from 25 down to 1.5 nm are formed in an oxide matrix after annealing. Under ultraviolet excitation, both types of films luminesce around 3.1 eV, with identical photoluminescence (PL) line shapes and subnanosecond PL dynamics. The strongest PL intensity was found for the films containing GeO2 crystals and for the largest nanocrystals. These results are a clear indication that although the blue luminescence is without a doubt correlated with the formation of Ge (or GeO2) nanocrystals, it is not produced by the radiative recombination of excitons confined in the nanocrystals. Possible mechanisms for the luminescence include defects at the nanocrystal/matrix interface or in the matrix itself.

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“…The amorphous germanium clusters crystallize. The growth of GeO crystals can be excluded as resulted from detailed X-ray investigations of the films [32].…”

Section: Discussionmentioning

confidence: 99%

The Preparation of Amorphous Si_xGe_yO_z Alloy Films by Sputtering. Preparation Conditions, Chemical Composition, and Vibrational Properties

Zacharias

Stolze

Drüsedau

et al. 1995

Physica Status Solidi (b)

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Amorphous Si,Ge,O, alloy films with x = 0.17 to 0.60, y = 0.19 to 0.68, and z = 0.11 to 0.42 are deposited using reactive dc magnetron sputtering in an Ar/water atmosphere. The alloy concentrations are measured by secondary neutral mass spectrometry (SNMS). The oxygen content strongly decreases with decreasing silicon concentration. The dependence of the alloy composition on the target coverage with germanium pieces is investigated. IR transmission measurements in the range from 400 to 4000 cm-' show a predominance of the Si-0-Si asymmetric stretching mode. The minor absorption band due to Ge-0-Ge stretching vibrations totally disappears after annealing the film at 800 "C. An increase of the Si-0-Si absorption mode is detected.Amorphe Si,Ge,O, Filme (mit x = 0,17 bis 0,60, y = 0,19 bis 0,68 und z = 0,ll bis 0,42) werden mit reaktivem DC-Magnetron Sputtern unter ArlWasserdampf-Atmosphare hergestellt. Die Konzentration der Legierungselemente wird mittels Sekundarneutralteilchenmassenspektroskopie untersucht. Mit der Abnahme der Silizium-Konzentration wird eine starke Verringerung des Sauerstoffgehaltes der Legierungen festgestellt. Die Abhangigkeit der Veranderung der Legierungszusammensetzung von der Targetbedeckung mit Germanium wird untersucht. IR-Transmissionsmessungen im Bereich von 400 his 4000 cm-zeigen eine Dominanz der asymmetrischen Si-0-Si Streckschwingung. Die schwache Absorptionsbande der Ge-0-Ge Streckschwingungen verschwindet nach dem Tempern auf 800 "C vollstandig und eine VergroBerung der Si-0-Si Absorptionsbande wird festgestellt.

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Formation of Ge nanocrystals in amorphous GeO x , and SiGeO x alloy films

Cited by 23 publications

References 14 publications

GeO_x/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li₂O along with Improved Rate Performance

GeO_x/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li₂O along with Improved Rate Performance

Blue luminescence in films containing Ge and GeO2 nanocrystals: The role of defects

The Preparation of Amorphous Si_xGe_yO_z Alloy Films by Sputtering. Preparation Conditions, Chemical Composition, and Vibrational Properties

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Formation of Ge nanocrystals in amorphous GeO x , and SiGeO x alloy films

Cited by 23 publications

References 14 publications

GeOx/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li2O along with Improved Rate Performance

GeOx/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li2O along with Improved Rate Performance

Blue luminescence in films containing Ge and GeO2 nanocrystals: The role of defects

The Preparation of Amorphous SixGeyOz Alloy Films by Sputtering. Preparation Conditions, Chemical Composition, and Vibrational Properties

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GeO_x/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li₂O along with Improved Rate Performance

GeO_x/Reduced Graphene Oxide Composite as an Anode for Li‐Ion Batteries: Enhanced Capacity via Reversible Utilization of Li₂O along with Improved Rate Performance

The Preparation of Amorphous Si_xGe_yO_z Alloy Films by Sputtering. Preparation Conditions, Chemical Composition, and Vibrational Properties