As so much of society depends on the transistors in our electronics, we face quite a challenge when they break down. Existing transistors are vulnerable to radiation and heat, inspiring a search for more stable options to send into orbit. One team thinks diamonds, renowned for their stability, might provide the answer, and has produced a thin transistor layer on a diamond substrate.
“Diamond is the perfect material to use in transistors that need to withstand cosmic ray bombardment in space or extreme heat within a car engine, in terms of performance and durability,” said Dr Zongyou Yin of the Australian National University in a statement.
Transistors control currents within electrical circuits using triple-stacked layers of semiconductors alternately doped with electron donors (n-type) and acceptors (p-types). Existing transistors are made from silicon carbide and gallium nitride, but neither lasts well in radioactive or high-temperature environments.
Yin modified commercially available artificial diamonds so they would act as a substrate and deposited a single atom layer of hydrogen on top. On this, he added a thin layer of molybdenum oxide (MoO3), doped with hydrogen atoms.
Diamonds may be very tough, but this would do little good if the deposited layers proved unstable. Yin told IFLScience the diamonds disperse heat and protect the layers above. Moreover, he added, the hydrogen doping makes for greater stability than molybdenum oxide alone.
In addition to the durability his devices offer, Yin added they are also exceptionally small and light, an advantage in many situations, but particularly for something that needs to be sent into space. Diamonds, even artificial ones, may be expensive, but these are so tiny the cost of production should be tolerable.
Yin has published his work in Science Advances, but admits it is only at the proof-of-principle stage. He told IFLScience he is keen to manufacture his own diamonds as part of the process of getting the transistors to the point where they can be produced for industrial applications.
Yin is not the first to experiment with diamond transistors. The fact that diamonds' surfaces behave as p-type semiconductors when covered with a hydrogen coating has attracted interest for 20 years, and has inspired efforts to add n-type layers to make transistors, but earlier efforts proved unstable under higher temperatures.
The paper also expresses confidence that a wide range of materials whose surfaces act as “extreme semiconductors” can be used as substrates for transition-metal oxides. Potential applications include better solar cells, sensing devices, and the destruction of toxic chemicals.