The authors report a simple and easy technique for the fabrication of nanogaps with separations of less than 10 nm. This technique is based on electromigration induced by field emission current. Here, the authors investigated the dependence of tunnel resistance on the shape of nanogap electrodes and initial gap separation. The initial nanogap electrodes having asymmetrical shape with the separation of 30-60 nm were fabricated by electron-beam lithography and lift-off process. In the nanogaps with asymmetrical shape, the tunnel resistance was controlled by the magnitude of the preset current during field-emission-induced electromigration and decreased from the order of 100 T Omega to 100 k Omega with increasing the preset current from 1 nA to 150 mu A. This tendency was quite similar to that of nanogaps with symmetrical shape. Furthermore, the tunnel resistance after the electromigration was less dependent on the initial gap separation and was completely determined by the preset current. This suggests that it is possible to control the tunnel resistance of nanogaps by field-emission-induced electromigration. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3039683]