Diamond is an effective electrical insulator, but according to a new study by the Massachusetts Institute of Technology and Nanyang Technological University (NTU) in Singapore, this may not always be the case. The research team calculated that deforming the diamond nanoneedles would change its conductivity from an insulator to a semiconductor, then to a highly conductive metal, and then back again at will.

Material strain seems to be something that all walks of life usually want to avoid, but in some cases, it can make materials better. For example, strained silicon can allow electrons to pass through it more easily and increase the switching speed of a transistor by 35%, but the key to all this is to apply enough strain to affect the arrangement of atoms in the crystal lattice, but not too much. So large that the lattice itself is destroyed.

How easy it is for electrons to move in a material is measured by the “bandgap” of the material. The larger the bandgap, the more difficult it is for electrons to pass. At 5.6 Electronic Ford (eV), diamond usually has an ultra-wide band gap, making it an insulator. But in the new study, the researchers found a way to strain the diamond to change its band gap.

The research team used quantum mechanics and computer simulations of mechanical deformation and found that diamond probes can be used to bend diamond nanoneedles into varying degrees of strain. The greater the strain applied, the narrower the band gap until it disappears completely just before the needle will break. At this point, the diamond has completed “metallization” and transformed into an excellent electrical conductor.

“We found that the band gap can be reduced from 5.6 electron volts to 0,” said Ju Li, the corresponding author of the study. “If you can continuously change from 5.6 electron volts to 0 electron volts, you can cover all band gaps. Through strain engineering, diamond can have the band gap of silicon, which is the most widely used semiconductor or gallium nitride band gap. At the same time, it is widely used in LEDs. It can even be used as an infrared detector, or detect the entire range of light from infrared to ultraviolet light in the spectrum.”

The team said that the new technology may bring a series of interesting applications. For example, solar cells can be used to capture a wider range of light frequencies on a single device. This work currently requires stacking of different materials. This technology can also make new types of quantum detectors and sensors.

With its excellent properties, diamond has been widely used in high-end manufacturing industries such as precision tools, wear-resistant parts, optical component coatings, and electronic product parts processing. In addition, diamond is not only an “industrial tooth”, but also an “ultimate semiconductor”. The third-generation wide-bandgap semiconductors and devices represented by diamond are the foundation of future integrated circuits and the development of the information age. They are used in biological testing, medical treatment, flat panel display, and environmental protection. Many high-tech fields such as engineering and functional devices have huge application potential.