So long, silicon – are diamond transistors the future of electronics?

The consumer electronics boom is built on microchips packed with millions or billions of tiny transistors, usually made from silicon. But although silicon has driven the growth of computers, it does have some limitations – it tends to fail when exposed to high temperatures or high levels of radiation.

Transistors made of diamond could solve some of those problems, according to a paper published this week in the journal Applied Physics Letters by Jiangwei Liu and colleagues from Japan’s National Institute for Material Science. “Manufactured diamonds have a number of physical properties that make them very interesting to researchers working with transistors," said Yasuo Koide, a professor at the National Institute for Materials Science.

"Not only are they physically hard materials, they also conduct heat well, which means that they can cope with high levels of power and operate in hotter temperatures," said Koide. They can also "endure larger voltages than existing semiconductor materials before breaking down," he added.

However, Steve Hall, a professor of electrical engineering and electronics at the University of Newcastle, told Professional Engineering that devices with diamond transistors were unlikely to replace silicon chips in smartphones. But, Hall said, they could be used for power devices and “rad-hards” - electronic components which have been shielded from radiation.

Diamond has a wider ‘band gap’ than silicon, a key factor in determining its electrical conductivity.  “From the point of view of power transistors, that translates to a higher breakdown voltage, so you can use them in a lot more applications than silicon,” said Hall. “You can put a lot of voltage in them before they break down.”

Diamond transistors could therefore be more versatile and energy efficient. The team have developed a new fabrication process to make them, using a technique called electron beam evaporation. This method involved using a beam of electrons to coat diamond with a layer of yttrium oxide, to form a voltage gate for the transistor. The input voltage through the gate determines whether the transistor will conduct electricity or not.

"Another innovation was that the yttrium oxide was deposited as a single layer," said Liu. "In our previous work, we have created oxide bi-layers, but a single layer is appealing because it's less difficult and less expensive to manufacture."

Koide said that ultimately, the team's goal is to build integrated circuits with diamonds. "With this in mind, we hope our work can support the development of energy-efficient devices that can function in conditions of extreme heat or radiation," he added.