Diamond, the hardest of the natural minerals, perfectly conducts heat, but not electricity. Specialists from the U.S. have found a way to gradually change the electronic properties of tiny diamond needles, so that they become first semiconducting and then conductive, like metal. These properties can be induced dynamically and, if desired, to turn off without degradation of the material.
The MIT team of scientists used quantum-mechanical calculations, mechanical deformation analysis and machine learning to demonstrate a phenomenon that for a long time could only exist in theory.
The idea of deformation of a semiconducting material, such as silicon, to improve its performance, found application in microelectronics more than 20 years ago. However, this approach leads to a small deformation of about 1%. Professor Li Ju and his colleagues have been studying the concept of elastic deformation for many years, based on the ability to cause significant changes in electrical, optical, thermal and other properties of materials by simply changing their shape, MIT News writes.
In 2018, they showed that nanometer long diamond needles can bend without breaking at room temperature. They brought the tensile strain to 10%, after which the needles returned to their original shape.
The key concept here is the energy slot, which determines how easily electrons can move through the material. Usually, in diamonds, it is very wide – 5.6 electron volts. This means that diamonds are a good insulator.
The latest experiments of Professor Lee’s team have shown that the energy slot of a diamond can be changed gradually, continuously and reversibly, giving the material different properties, from insulator to semiconductor to metal.
“We found it is possible to reduce the energy slot from 5.6 electron volts to zero,” Lee said. – The point is that if you can change it continuously from 5.6 electron volts to zero, you can cover the entire range of the energy gap. By elastic deformation, you can make the diamond have an energy slot in silicon, a common semiconductor, or gallium nitride, which is used for LEDs. It can even be used to make an infrared detector, or an entire light spectrum detector, from infrared to ultraviolet.