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

H. Kabbara,K. Hussein,J. Ghanbaja,V. Švrček,C. Noël,T. Belmonte,D. Mariotti

doi:10.1038/srep17477

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.

Highlights

The synthesis feasibility of silicon–tin nanocrystals by discharges in liquid nitrogen is studied using a Si–10 at % Sn sintered electrode
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
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

Summary

Introduction

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. When the sintered electrode is hit by powerful discharges, some grains are heated and tin diffuses in the large silicon crystals. These grains are shelled and fall into the dielectric liquid. The optical band gap of Si–Sn NCs would be direct and not indirect like in silicon and it could be tuned since it depends on both the tin content and the NC size.

Methods

Results

Conclusion