A nanometre scale gap (nanogap) structure in palladium strip fabricated by hydrogen absorption under high-pressure treatment was proposed and applied to the surface conduction electron emitter for flat panel displays. In this paper we demonstrate that the structure possesses different high field-emission efficiencies with low turn-on voltages and high focused capability, compared with the conventional type. An experimentally validated simulation is conducted to investigate the field-emission characteristics of the explored structure. It is observed the inclined sidewall and protrusion of this nanogap can enhance the local electric field and the focused capability and protect emission areas from being damaged by impurity ions during field-emission operation. This study benefits the advanced design of metallic electrodes in nanodevice technology for new types of electron sources and display applications.