  We developed a simple and reliable method for the fabrication of sub-10-nm
wide nanogaps. The self-formed nanogap is based on the stoichiometric
solid-state reaction between metal and Si atoms during silicidation process.
The nanogap width is deter- mined by the metal layer thickness. Our proposed
method produces nanogaps either symmetric or asymmetric electrodes, as well as,
multiple nanogaps within one unique process step for application to complex
circuits. Therefore, this method provides high throughput and it is suitable
for large-scale production. To demonstrate the feasibil- ity of the proposed
fabrication method, nanogap resistive switches have been built and
characterized. They exhibit a pronounced hysteresis with up to 103 on/off
conductance ratios in air. Our results indicate that the voltages for initially
electroforming the de- vice to the switch state are determinated by the nanogap
sizes. However, the set and reset voltages of the device do not strongly
dependent on the nanogap widths. These phenomena could be helpful to understand
how the resistive switching is established.
