Oxidation Resistance Enhancement of Graphene-Oxide-Semiconductor Planar-Type Electron Sources Using Al₂O₃ Thin Protective Coating by Atomic Layer Deposition

Graphene-oxide-semiconductor (GOS) planar electron-emitting devices with an aluminum oxide (Al₂O₃) protective layer were found to improve oxidation resistance and to be capable of emitting electrons through a protective film on the device. An electron-transparent oxidation resistance layer for the GOS device was achieved with a uniform 3 nm Al₂O₃ deposited by atomic-layer deposition at a low temperature of 100 °C after precleaning with H₂O. A high electron emission current density of 1.01 mA/cm² and a high electron emission efficiency of 0.49% were obtained from the GOS electron-emitting device with the uniform 3 nm Al₂O₃ protective film. The energy distribution of the electrons emitted from the GOS device with an Al₂O₃ protection layer was higher than the work function of the graphene electrode, which indicated that the primary factor in the degradation of electron emission efficiency of the GOS device by the Al₂O₃ protection layer was not the energy loss of the emitted electrons due to inelastic electron scattering within Al₂O₃ but the electron backscattering at the protection layer due to elastic electron scattering. These results suggest that the electron emission efficiency and current density of oxygen-tolerant GOS devices could be further improved by a uniform Al₂O₃ protective layer with a thickness below the mean free path of electron elastic scattering within Al₂O₃.