Silicon Oxide Electron‐Emitting Nanodiodes

Electrically driven on‐chip electron sources that do not need to be heated are long pursued, but their realization remains challenging. Here, it is shown that a nanogap formed by two electrodes on a silicon oxide substrate functions as an electron‐emitting nanodiode after the silicon oxide in the nanogap is electrically switched to a high‐resistance conducting state. A nanodiode based on graphene electrodes can be turned on by a voltage of ≈7 V in ≈100 ns and show an emission current of up to several microamperes, corresponding to an emission density of ≈106 A cm−2 and emission efficiency as high as 16.6%. We attribute the electron emission to be generated from a metal–insulator–metal tunneling diode on the substrate surface formed by the rupture of conducting filaments in silicon oxide. An array of 100 nanodiodes exhibits a global emission density of 5 A cm−2 and stable emission with negligible current degradation over tens of hours under modest vacuum. The combined advantages of a low operating voltage, fast temporal response, high emission density and efficiency, convenient fabrication and integration, and stable emission in modest vacuum make silicon oxide electron‐emitting nanodiodes a promising on‐chip electron sources. By electrically forming a surface metal–insulator–metal tunneling diode in silicon oxide, a nanogap spaced by two electrodes on a silicon oxide substrate functions as an electron‐emitting nanodiode with low operating voltage, fast temporal response, and dense, efficient, and stable emission in a modest vacuum. The outstanding electron emission performances make the electron‐emitting nanodiode a promising on‐chip electron source.