Could diamond be the new silicon?
Little known is the fact that the physical properties of diamond actually surpass those of silicon. Recent use of diamond to power electronics has opened the path to a more durable future, where transistors size is shrunk by a factor of 100’000, and electric cars charged within seconds.
Silicon is today the most widely used semiconductor in electronic components such as diodes and transistors; invisible but critical building blocks within the microprocessors powering smart technologies.
However, silicon has its limits: it ceases to operate properly at temperatures above 180°C and cannot endure high voltages; two serious downsides for electronic components functioning close to a heat source, such as reactors, and more broadly for the whole power electronics field.
These constraints are holding back the integration of multiple high power sources into a single electricity supply network, those so-called “smart grids”, hindering in turn the deployment of renewable energy such as solar, geothermal and wind power.
Diamond is actually providing an alternative to overcome those roadblocks at is allows electronic systems to withstand the very high voltage electricity produced by power stations, and transform it into low voltage current that can be used in homes. Taking advantage of those benefits could allow charging electric vehicles within seconds, and reduce chargers’ size by a factor of 100’000. For the time being, only diamond permits converters to operate at higher frequencies and at higher temperatures.
Diamond “on steroids”
Its unique properties such as exceptional heat conductivity and extreme breaking voltage — critical conditions to withstand significant differences in voltage — put diamond in a class well ahead of all other materials
“Diamond has all the physical properties useful in power electronics. It’s incredible! Even though other materials may have properties that outperform diamond on an individual level, diamond combines them all, and that’s what makes it unique,”
says Mehdi Naamoun, Director of Diamond Development Operations at LakeDiamond.
Diamond is also an electrical insulator at room temperature and can be transformed into semiconductors, just like silicon. That means it can be used to make diodes and transistors, the basic components of nearly all electronic devices. Pure diamond is made up of carbon atoms that form a unique three-dimensional, extremely stable structure. That stability makes diamond a perfect insulator, preventing the movement of free electrons. Electrons can then be set in motion by changing their network, replacing carbon atoms with elements that are electron acceptors (boron) or electron donors (phosphorus or nitrogen). This process is called doping.
Impurities made to measure
Diamonds can now be grown in laboratories and their composition controlled. LakeDiamond, based on the EPFL campus, is an expert in growing diamonds of rare purity. And that is essential in doping. With its 25 employees, the Vaud-based start-up builds on its expertise to develop its own doping techniques.
“When growing diamond, we introduce substitute atoms in gas form in a controlled way to alter the atomic structure of our diamond,” Dr Naamoun says.
Researchers have been working on doping diamond for about 10 years, but further development is needed. Dr Naamoun says that the size of the precious stones is another major problem.
“We need to produce diamonds that are 300 millimetres in diameter, the size of silicon wafers for microprocessors, to integrate millions of transistors. Currently, we can make diamonds that are 25 millimetres in diameter at most.”
Despite these obstacles, hybrid solutions exist, and at LakeDiamond, we hope to launch our first all-diamond electronic components by 2022.
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