Turning diamond into metal | MIT News

Said to be the hardest of all pure supplies, diamonds are also typical thermal conductors and electrical insulators. Now, researchers have discovered a technique to remap tiny diamond needles to their digital properties in a managed technique, the best way to make them extremely conductive, or metal, through semiconductors. It can be induced dynamically and reversed at will without corrosion of the diamond material.

The analysis, although in an early proof-of-concept stage, could open up a wide selection of potential functions, together with new types of broadband photo voltaic cells, extremely environmentally friendly LED and energy electronics, and new optical units or quantum sensors, the researchers said. Is said.

Their findings, which are based mostly on simulations, calculations and prior experimental results, are reported this week within the Proceedings of the Nationwide Academy of Sciences.

The paper is by MIT professor Xu Li and graduate scholar Jay Xi; Principal Analysis Scientist Ming Dao; Professor Subra Suresh, who is President of Nanyang Technological College in Singapore, also former Dean of Engineering and Vannevar Bush Professor Emeritus at MIT; and Evgeny Tsimbalov and Alexander Shepev at the Skolkovo Institute of Science and Know-How in Moscow.

The task force used a mix of quantum mechanical calculations, analysis of mechanical deformation, and machine studies to demonstrate that the phenomenon, long theorized as exposure, could indeed occur in nanosized diamonds.

The idea of ​​filtering a semiconductor material similar to silicon to increase its efficiency was explored within the microelectronics business more than twenty years ago. Still, that strategy involved small currents on the order of about 1%.

Lee and his colleagues have spent years creating the idea of ​​elastic pressure engineering. It is based primarily on the flexibility of triggering significant modifications within the electrical, optical, thermal, and other properties of the supply by simply deforming them—by placing them under enormous mechanical pressures from the average, geometries of atoms within the material’s crystal. Enough to change the union. lattice, though without disrupting that lattice.

In a significant advance in 2018, a task force led by Suresh, Dao and Lu Yang of the Polytechnic College of Hong Kong confirmed that tiny diamond needles, only a few hundred nanometers, can be bent to huge strains without fracture at room temperature. Huh. . They have been able to bend these nanoneedles repeatedly under tensile pressures up to 10%; The needles can then remain intact in their unique form.

Key to this work is a property called the bandgap, which basically determines how easily electrons can move through the fabric.

Thus this property is the key to the electrical conductivity of the fabric. Diamond typically has a very wide bandgap of 5.6 electron volts, which means it is a strong electrical insulator that does not move electrons easily. In their latest simulations, the researchers present that the diamond bandgap can be modified continuously, continuously and reversibly, providing a variety of {electrical} properties from semiconductors to metals to insulators.

“What we found is the ability to cut the bandgap back from 5.6 electron volts to zero all the best,” says Lee. “The purpose of this is that if you can continuously change from 5.6 to 0 electron volts, you cover all of the variation of the bandgap.

By pressure engineering, you can also make diamond the bandgap of silicon, commonly referred to as a semiconductor, or gallium nitride, which is used for LED’s. You could probably even make it an infrared detector or detect the full range of sunlight from infrared to a part of the spectrum all the way up to ultraviolet can put.

“The flexibility to engineer and design electrical conductivity without altering the chemical composition and stability of the diamond gives unprecedented flexibility to custom-design its capabilities,” says Suresh. “The strategies demonstrated on this work could potentially be used through pressure engineering to supply a variety of semiconductors of technical curiosity in mechanical, microelectronics, biomedical, power and photonics tasks.”

So, for example, a small piece of diamond, so that there is a gradient of pressure around it, could be a photo voltaic cell capable of capturing all frequencies of sunlight on a single machine – one thing is that current can only be obtained through tandem units that pairs different types of photo voltaic cells supplied collectively in layers to combine their different absorption bands.

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