Diamonds reigns supreme for high-power, high-temperature microelectronics, and optoelectronics due to its numerous advantages over traditional semiconductors, such as ultrawide bandgap, ultrahigh thermal conductivity, high dielectric breakdown strength, and carrier mobility.
However, the wide bandgap and tight crystal structure of diamonds make it challenging to "dope," a typical method used to modulate the electrical properties in semiconductor production, which hampers its commercial applications in electronic and optoelectronic devices. "Strain engineering" is one of the possibilities that could change the electronic band structure and corresponding functional characteristics by introducing lattice strain in crystalline materials. Diamonds, however, were thought to be quite impossible to be altered in this way owing to its extraordinarily high hardness and brittleness.
Chaoqun Dang created diamond tensile bridge samples up to 1-2 μm in length by 100-300 nm in width with well-defined geometry and crystal orientations by using advanced microfabrication processes from bulk single-crystalline diamonds. Those diamond bridges subsequently were uniaxially stretched in a controllable manner within an electron microscope. Under continuous and well-controlled loading-unloading cycles of quantitative tensile tests, the diamond bridge displayed a highly uniform, huge elastic strain of up to 10%.
Meanwhile, she further confirmed the “deep elastic strain engineering” of diamonds where the bandgap generally decreased as the tensile strain increased and even could change from indirect to direct by density functional theory (DFT) calculations and electron energy-loss spectroscopy analysis. She further realized the elastic straining of microfabricated diamond arrays with larger sizes ranging from nanoscales to microscales, which demonstrates the “strained diamond” device concept.
These discoveries offer immense application potential for diamond’s deep elastic strain engineering in photonics, electronics, and quantum information technology.