Low-power-consumption, high-current-density, and propellantless cathode using graphene-oxide-semiconductor structure array

Graphene-oxide-semiconductor (GOS) planar-type electron sources—which consist of a graphene electrode layer, a thin SiO2 insulator, and a Si substrate—can be driven by applying gate biases of 5–15 V to produce high emission current densities of 10–100 mA/cm2. In this study, propellantless cathodes using GOS electron sources are developed for aerospace applications. Because a single emission site usually has an area smaller than 100 μm × 100 μm, its maximum emission current is below 10 μA. To increase the emission current to several milliamperes or more, the total emission area must be expanded. However, it is difficult to increase the emission current by merely enlarging a single emission area because the graphene layer acts not only as the gate electrode but also as a series resistor, which means that the emission current density decreases as the effective gate bias decreases. Thus, the optimum relationship between the area of a single emission site and the emission current of the site array is investigated, showing a result that an electron source with hundreds of 100 μm × 100 μm sites on a 3 mm × 3 mm wafer produces an emission current of 6.0 mA at a gate bias of 11.1 V. •The cathode can be driven at ~15 V with emission current densities of ~100 mA/cm2.•A relationship between a single emission area and the array pattern is optimized.•The array cathode on a 3 × 3 mm2 wafer produces an emission current of 6.0 mA.