High-pressure Pd hydrogenation was used to fabricate a single nanogap on the Pd strip electrode of the surface-conduction electron emitter (SCE). The large stress induced by the Pd hydrogenation resulted in formation of a nanogap in the Pd electrode at the step area over the PtTi contact pad in the SCE structure. The gap width was a function of not only Pd hydrogenation conditions but also the dimension of the SCE structure. Finite element analysis was used to study the stress distribution in the SCE structure with the PtTi contact pad of various thicknesses so that an SCE structure with a minimized gap width could be obtained. Among the SCE emitters under study, the optimal SCE structure, which was with a PtTi contact pad thickness of 20 nm and had a Pd nanogap width of 18 nm, exhibited the best field-emission performance. Compared to the conventional SCE emitter with a planar nanogap, the hydrogenated SCE emitter demonstrated a much higher emission efficiency (∼4%). The better electron emission performance of the hydrogenated SCE emitter was ascribed to so that the emitter cathode had a rugged and protruding edge structure.