The transistors can withstand far higher working temperatures than conventional ones, are resistant to corrosive chemicals and would even be safe to implant in body tissue, the inventor's patent suggests. The tricky part is making sure the diamonds connect and conduct properly.
To make them, pure diamond vapour is deposited at around 900В°C to form a wafer base. More diamond vapour doped with nitrogen to make it conductive, is then layered on top.
Liquid molybdenum is then selectively deposited onto the conductive diamond, to make electrical contacts, and the sandwich is topped with even more diamond, this time mixed with hydrogen, to insulate it electrically. The molybdenum spots do not bond with the hydrogen-doped diamond, so they poke through the surface and act as connector electrodes.
All-diamond chips would be way too expensive for everyday civilian use, but the researchers have found a cheaper solution that works almost as well. Instead of a pure diamond wafer base, they use conventional silicon covered with a thin layer of insulating oxide, which is then coated with a layer of conductive diamond.
Read the full patent here.
