Potential High-Speed Switching Nano-Device with Sub-Nanometer Gaps

We investigate the electrical response of a device with sub-nanometer gaps, which potentially can be used as an ultrafast optical switch. In todays electronics, semiconductor devices at best have a picosecond response time. Making structural change is one way to achieve faster electronics. The Coulomb blockade effect in tunnel junctions can reproduce a highly nonlinear response current, which is required for a switch. However, a tiny capacitance is necessary for a femtosecond time constant. A sub-nanometer gap with a small surface area can satisfy both of these conditions. The nonlinear optical switching behavior of a sub-nanometer gap has been observed experimentally [1]. It is a potential candidate for an effective and low-cost switch with high speed operation. We fabricated a gold on silicon sample with sub-nanometer gaps filled by self-assembled monolayer and then we illuminated it with a femtosecond pulsed laser. We recorded the dark current and photocurrents of the sample with different incident powers. This experimental report can pave the way for harnessing high-speed switching in nanodevices with sub-nanometer gaps.