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Synthesis of nanocrystals by discharges in liquid nitrogen from Si-Sn sintered electrode.

Kabbara H, Noël C, Ghanbaja J, Hussein K, Mariotti D, Švrček V, Belmonte T - Sci Rep (2015)

Bottom Line: The presence of both vapours does not lead to the synthesis of alloyed nanocrystals but to the synthesis of separate nanocrystals of silicon and tin with average sizes of 10 nm.The synthesis of an am-Si0.95Sn0.05 phase around large silicon crystals (~500 nm) decorated by β-Sn spheroids is achieved if the current flowing through electrodes is high enough.When the sintered electrode is hit by powerful discharges, some grains are heated and tin diffuses in the large silicon crystals.

View Article: PubMed Central - PubMed

Affiliation: Université de Lorraine, Institut Jean Lamour, UMR CNRS 7198, NANCY, F-54042, France.

ABSTRACT
The synthesis feasibility of silicon-tin nanocrystals by discharges in liquid nitrogen is studied using a Si-10 at % Sn sintered electrode. Time-resolved optical emission spectroscopy shows that silicon and tin melt almost simultaneously. The presence of both vapours does not lead to the synthesis of alloyed nanocrystals but to the synthesis of separate nanocrystals of silicon and tin with average sizes of 10 nm. These nanocrystals are transformed into amorphous silicon oxide (am-SiO2) and β-SnO2 by air oxidation, after evaporation of the liquid nitrogen. The synthesis of an am-Si0.95Sn0.05 phase around large silicon crystals (~500 nm) decorated by β-Sn spheroids is achieved if the current flowing through electrodes is high enough. When the sintered electrode is hit by powerful discharges, some grains are heated and tin diffuses in the large silicon crystals. Next, these grains are shelled and fall into the dielectric liquid.

No MeSH data available.


Related in: MedlinePlus

Large-view TEM image of a Si-Sn sample synthesized with a current of 1 A with examples (white circles) of crystalline domains.
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f1: Large-view TEM image of a Si-Sn sample synthesized with a current of 1 A with examples (white circles) of crystalline domains.

Mentions: In Fig. 1, a large-view transmission electron microscope (TEM) image, which is representative of the analysed samples obtained with a current of 1 A, shows the presence of crystalline nanoparticles spread in an amorphous matrix. Identifying the various phases synthesized by pulsed discharges in liquid nitrogen is complex. Indeed, one might expect to find Si, α-Sn, β-Sn, SiO2, SnO2, Si1–xSnx and (Si1–xSnx)O2. Unreported micro-energy dispersive spectroscopy (EDS) analysis shows that our samples contain in average 80.7 at %Si, 6.2 at %Sn and 13.1 at %O, giving a Sn/Si atomic ratio which is almost the same as in the target. To ease identification, electron energy loss spectroscopy (EELS) is used prior to indexation of micro-diffraction patterns. Figure 2a shows EEL spectra at the Si-L3,2 edge of a representative sample of NCs synthesized with a current of 1 A. The presence of amorphous SiO2 (am–SiO2) is observed in all samples, where various NCs are embedded. The EEL spectrum at the Sn-M4,5 edge indicates that tetragonal SnO2 (β–SnO2) NCs are present (Fig. 2b and see Supplemental Material 4 for high-resolution TEM images of diamond tetragonal β–SnO2 NCs), however no Si1–xSnx or (Si1–xSnx)O2 can be observed. If silicon NCs were to be present, these would have been largely oxidized, making it difficult to detect the presence of any crystalline Si (c-Si) material. Indeed, air oxidation is efficient and turns Si NCs into amorphous15. Unreported results about discharges in liquid nitrogen between two crystalline silicon electrodes show clearly that Si NCs with larger diameters lying in the range 10–20 nm are synthesized. When diameters are large enough, oxidation is limited by the synthesis of a passive SiO2 outer shell, leaving an oxygen-free silicon core. These results agree well with those obtained by Kobayashi et al.16.


Synthesis of nanocrystals by discharges in liquid nitrogen from Si-Sn sintered electrode.

Kabbara H, Noël C, Ghanbaja J, Hussein K, Mariotti D, Švrček V, Belmonte T - Sci Rep (2015)

Large-view TEM image of a Si-Sn sample synthesized with a current of 1 A with examples (white circles) of crystalline domains.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664926&req=5

f1: Large-view TEM image of a Si-Sn sample synthesized with a current of 1 A with examples (white circles) of crystalline domains.
Mentions: In Fig. 1, a large-view transmission electron microscope (TEM) image, which is representative of the analysed samples obtained with a current of 1 A, shows the presence of crystalline nanoparticles spread in an amorphous matrix. Identifying the various phases synthesized by pulsed discharges in liquid nitrogen is complex. Indeed, one might expect to find Si, α-Sn, β-Sn, SiO2, SnO2, Si1–xSnx and (Si1–xSnx)O2. Unreported micro-energy dispersive spectroscopy (EDS) analysis shows that our samples contain in average 80.7 at %Si, 6.2 at %Sn and 13.1 at %O, giving a Sn/Si atomic ratio which is almost the same as in the target. To ease identification, electron energy loss spectroscopy (EELS) is used prior to indexation of micro-diffraction patterns. Figure 2a shows EEL spectra at the Si-L3,2 edge of a representative sample of NCs synthesized with a current of 1 A. The presence of amorphous SiO2 (am–SiO2) is observed in all samples, where various NCs are embedded. The EEL spectrum at the Sn-M4,5 edge indicates that tetragonal SnO2 (β–SnO2) NCs are present (Fig. 2b and see Supplemental Material 4 for high-resolution TEM images of diamond tetragonal β–SnO2 NCs), however no Si1–xSnx or (Si1–xSnx)O2 can be observed. If silicon NCs were to be present, these would have been largely oxidized, making it difficult to detect the presence of any crystalline Si (c-Si) material. Indeed, air oxidation is efficient and turns Si NCs into amorphous15. Unreported results about discharges in liquid nitrogen between two crystalline silicon electrodes show clearly that Si NCs with larger diameters lying in the range 10–20 nm are synthesized. When diameters are large enough, oxidation is limited by the synthesis of a passive SiO2 outer shell, leaving an oxygen-free silicon core. These results agree well with those obtained by Kobayashi et al.16.

Bottom Line: The presence of both vapours does not lead to the synthesis of alloyed nanocrystals but to the synthesis of separate nanocrystals of silicon and tin with average sizes of 10 nm.The synthesis of an am-Si0.95Sn0.05 phase around large silicon crystals (~500 nm) decorated by β-Sn spheroids is achieved if the current flowing through electrodes is high enough.When the sintered electrode is hit by powerful discharges, some grains are heated and tin diffuses in the large silicon crystals.

View Article: PubMed Central - PubMed

Affiliation: Université de Lorraine, Institut Jean Lamour, UMR CNRS 7198, NANCY, F-54042, France.

ABSTRACT
The synthesis feasibility of silicon-tin nanocrystals by discharges in liquid nitrogen is studied using a Si-10 at % Sn sintered electrode. Time-resolved optical emission spectroscopy shows that silicon and tin melt almost simultaneously. The presence of both vapours does not lead to the synthesis of alloyed nanocrystals but to the synthesis of separate nanocrystals of silicon and tin with average sizes of 10 nm. These nanocrystals are transformed into amorphous silicon oxide (am-SiO2) and β-SnO2 by air oxidation, after evaporation of the liquid nitrogen. The synthesis of an am-Si0.95Sn0.05 phase around large silicon crystals (~500 nm) decorated by β-Sn spheroids is achieved if the current flowing through electrodes is high enough. When the sintered electrode is hit by powerful discharges, some grains are heated and tin diffuses in the large silicon crystals. Next, these grains are shelled and fall into the dielectric liquid.

No MeSH data available.


Related in: MedlinePlus