Observation of a guest-free Si<sub>46</sub> clathrate-I framework from Ba<sub>8-x</sub>Si<sub>46</sub> upon in situ vacuum heating.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41107244.
- Also identified by DOI 10.1038/s41467-025-64277-2 and PMC identifier 12534387.
- Licence recorded as CC BY-NC-ND.
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Abstract
Silicon and its composites are key materials owing to their extensive use in the semiconductor industry. While the diamond-structured form dominates, other allotropes with superior properties at ambient conditions remain of interest. Toward this, Si<sub>46</sub> clathrate type-I crystals containing alkali/alkaline-earth metals have been extensively studied, but the experimental observation of a guest-free Si<sub>46</sub> structure has been challenging. Using advanced electron microscopy, we show experimental evidence of guest-free clathrate-I Si<sub>46</sub> framework from Ba<sub>8-x</sub>Si<sub>46</sub> under in situ heating. We reveal the stepwise Ba evacuation process, starting with loss of Ba1 from the smaller cages to form Ba<sub>6</sub>Si<sub>46</sub>, followed by removal of Ba2 in larger cages to reach Si<sub>46</sub> that appears in the thin region of the nanocrystal with a thickness around 4-6 nm at 500 °C. Calculations give a quasi-direct bandgap of 1.89 eV and support the preferential evacuation of Ba1. The observation of this guest-free Si<sub>46</sub> framework opens up possibilities for applications in high-speed transistors, optoelectronic devices or solar cell technologies.