Structural Modulation and BC8 Enrichment of Silicon via Dynamic Decompression

The modern very large-scale integration systems based on silicon semiconductors are facing unprecedented challenges especially when transistor feature size lowers further, due to the excruciating tunneling effect and thermal management. Besides the common diamond cubic silicon, numerous exotic silicon allotropes with outstanding properties can emerge under high pressure, such as the metastable BC8 and metallic β-tin structures. Despite much effort on the controlled synthesis in experiment and theory, the effective approach to rationally prepare Si phases with desired purity is still lacking, and their transition mechanism remains controversial. Herein, we systematically investigated the complicated structural transformations of Si under extreme conditions and efficiently enriched the BC8-Si phase via an ultraslow decompression strategy. The splendid purity of BC8-Si was achieved up to ∼95%, evidently confirmed by Raman spectroscopy and synchrotron X-ray diffraction. We believe that these results can shed light on the controlled preparation of Si metastable phases and their potential applications in nanoelectronics.