Development of planar type electron emission devices using a heterostructure of two-dimensional materials

A planar-type electron emission device has a capability of electron emission in low vacuum and even in an atmospheric pressure gas and liquid. Its unique feature will open novel applications, such as a direct reforming of gas and liquid materials by electron beams. There are, however, the critical issues of the very low electron emission efficiency and large energy spread of the electron beams of the devices due to the large electron scattering within the insulating layer and topmost gate electrode. In this study, to suppress the electron scattering within the device structure, the planar-type electron emission device using a heterostructure of graphene/h-BN directly deposited on a Si substrate were fabricated and their electron emission properties were evaluated. High electron emission current density of $3.12 \mathrm{mA} / \mathrm{cm}^{2}$ was achieved by the directly deposited graphene/h-BN heterostructure.