Formation of Hybrid Silicon Nanostructures via Capillary Instability Triggered in Inductively‐Coupled‐Plasma Torch Synthesized Ultra‐Thin Silicon Nanowires

• Published in: physica status solidi (b) Vol. 256; no. 7
• Main Authors: Agati, Marta, Castrucci, Paola, Dolbec, Richard, El Khakani, My Ali, Boninelli, Simona
• Format: Journal Article
• Language: English
• Published: 01.07.2019
• Subjects: capillary instabilities; hybrid nanostructures; inductively coupled plasma; silicon nanostructures; transmission electron microscopy
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.201800620

This paper provides a report on the formation of two main classes of hybrid silicon nanostructures via the capillary instability induced in ultra‐thin silicon nanowires (SiNWs) when subject to high temperature annealing. The first class of hybrid Si nanostructures shows a high‐level nanostructural order, and regroups (i) periodic strings of almond‐shaped Si nanocrystals (SiNCs) having average dimension of 3 nm and connected by ultra‐thin (≈2 nm) SiNWs and (ii) spherical SiNC chains (mean diameter of 6 nm, spaced by 16 nm on average), both embedded into silica NWs. In the second class of hybrid Si nanostructures, the SiNCs have different dimensions (in the 3–14 nm size range) and shapes, or a modulated Si core inside a SiO2 shell, thus exhibiting much higher nanostructural complexity. The self‐assembly of such nanostructures is related to the gas ambient under which the thermal treatment is performed. However, by increasing the annealing temperature, the SiNWs’ cores preferentially evolve toward the spherical SiNC chain morphology. The ultra‐thin diameter (2–3 nm) of the initial SiNWs is a key feature to induce the hybrid Si nanostructures formation. This study opens up the prospects of in situ controlling the formation of Si nanocrystals inside silica NWs, which will lead to the tailoring of their optoelectronic properties. Hybrid Si nanostructures are produced by subjecting to thermal treatments, under different ambient gas, ultra‐thin silicon nanowires (diameter 2–3 nm) synthesized via inductively coupled plasma. Their formation is ascribed to the capillary instability developed in the ultra‐thin Si core. The resulting hybrid Si nanostructures consist of a string of Si nanocrystals with different shapes and dimensions embedded in silica nanowires.