Ultraviolet light emissions from N2 microplasma electrically induced by metal–insulator–semiconductor devices

Various metal–insulator–semiconductor (MIS) devices in the form of Au/SiOx(x<2)/Si, Au/AlOy(y<1.5)/Si, Au/SiOx/ZnO and Au/AlOy/ZnO have been fabricated. For each device, once a sufficiently high positive voltage is applied on the Au electrode, the same ultraviolet (UV) emission with a spectrum featuring several specific peaks is detected. Interestingly, such UV emissions related to the MIS devices originate from the external N2 microplasma. It is believed that at the high enough positive voltages the highly energetic electrons emitted out of the Au electrode activate the air to generate the N2 microplasma.