Credit: Z. Shi et al., Proc. Natl. Acad. Sci. USA 117, 24634 (2020)
Topics: Materials Science, Modern Physics, Nanotechnology, Semiconductor Technology
If you ever manage to deform a diamond, you’re likely to break it. That’s because the hardest natural material on Earth is also inelastic and brittle. Two years ago, Ming Dao (MIT), Subra Suresh (Nanyang Technological University in Singapore), and their collaborators demonstrated that when bulk diamonds are etched into fine, 300-nm-wide needles, they become nearly defect-free. The transformation allows diamonds to elastically bend under the pressure of an indenter tip, as shown in the figure, and withstand extremely large tensile stresses without breaking.
The achievement prompted the researchers to investigate whether the simple process of bending could controllably and reversibly alter the electronic structure of nanocrystal diamond. Teaming up with Ju Li and graduate student Zhe Shi (both at MIT), Dao and Suresh have now followed their earlier study with numerical simulations of the reversible deformation. The team used advanced deep-learning algorithms that reveal the bandgap distributions in nanosized diamond across a range of loading conditions and crystal geometries. The new work confirms that the elastic strain can alter the material’s carbon-bonding configuration enough to close its bandgap from a normally 5.6 eV width as an electrical insulator to 0 eV as a conducting metal. That metallization occurred on the compression side of a bent diamond nanoneedle.
Diamond nanoneedles turn metallic, R. Mark Wilson, Physics Today