We explore novel nanometer-scale gaps with different widths in palladium (Pd) thin-film strips using hydrogen absorption under high-pressure conditions and different temperatures. Both the experimental measurement and numerical calculation are conducted to examine the electron conduction properties of the newly proposed surface conduction electron-emitters (SCEs). It is shown that this novel structure exhibits a high emission efficiency, so that a low turn-on voltage of 40 V for an SCE with a 30 nm nanogap is obtained. A calibrated model is adopted to predict the effects of the emitter thickness and different material work functions on emission current with different width of nanogaps. It is found that the heightened thickness increases the emission current. However, it tends to saturate for smaller nanogaps. The decrement of work function is proportional to the increase in emission current, which is independent of the width of nanogap.