Gallium oxide crystals, used to make power diodes, are extremely sensitive to damage. When a layer of nickel oxide is sputtered onto them, which is needed for the device to work, heavy ions bombard the surface like hail on fresh paint. After such a storm, the crystal loses its properties, and the diode starts conducting poorly.
Scientists came up with a shield: before sputtering, they applied an ultra-thin layer of nickel oxide onto the surface using a different method that does not damage the crystal. This layer, only 7 nanometers thick, acts as armor. Then they sputtered the rest of the coating on top of it, and the surface remained intact.
As a result, the diode withstood a voltage of 1.64 kilovolts, corresponding to an electric field of 4.02 megavolts per centimeter. This is a record for such devices. And the on-resistance increased only slightly, meaning the diode still conducts well. Now such diodes can be made cheaper and used in electric vehicles and data centers.
The critical field of β-Ga2O3 is roughly twice that of silicon carbide, allowing devices to be four times thinner at the same voltage. And the 7 nm NiOx layer used here is thousands of times thinner than a human hair.