New measurements explain how silicon and diamond achieve extreme reversible stretching

Researchers from the University of Hong Kong have uncovered the microscopic physical mechanisms behind the extreme elasticity of silicon and diamond. Led by Yang Lu, the team used advanced in situ high-resolution transmission electron microscopy and four-dimensional scanning transmission electron microscopy to directly observe the atomic-level displacement of lattice structures under tension.

By precisely quantifying the resulting lattice strains, the researchers established a direct link between macroscopic mechanical strain and microscopic atomic rearrangement. This discovery bridges the gap between the two seemingly contradictory properties of bulk covalent crystals: their hardness and brittleness, and their ability to undergo ultralarge, reversible deformation.

The team found that silicon and diamond can achieve sample-wide uniform elastic elongations of up to 11.3% and 8.9%, respectively, without the formation of defects or phase changes. The study also revealed that uniformly strained silicon exhibits a reduced band gap, demonstrating the potential for dynamic, continuous modulation of electronic properties.

This breakthrough in understanding the deformation mechanisms of covalent semiconductors paves the way for the development of next-generation electronic, optoelectronic, and quantum devices. The findings provide accurate atomic coordinates for deep strain states and establish a quantitative relationship between macroscopic mechanical strain and microscopic lattice strain.

With this new knowledge, researchers can now design semiconductor and photonic devices that exploit deep elastic strain engineering, potentially leading to significant advancements in quantum information processing, advanced semiconductors, and photonics.