Resistance switch employing a simple metal nanogap junction

Abstract

In recent years, several researchers have reported the occurrence of reversible resistance switching effects in simple metal nanogap junctions. A large negative resistance is observed in the I-V characteristics of such a junction when high-bias voltages are applied. This phenomenon is characteristic behaviour on the nanometre scale; it only occurs for gap widths slightly under 13 nm. Furthermore, such a junction exhibits a non-volatile resistance hysteresis when the bias voltage is reduced very rapidly from a high level to around 0 V, and when the bias voltage is reduced slowly. This non-volatile resistance change occurs as a result of changes in the gap width between the metal electrodes, brought about by the applied bias voltage.

Semiconductor-Free Nonvolatile Resistive Switching Memory Devices Based on Metal Nanogaps Fabricated on Flexible Substrates via Adhesion Lithography

“…This occurs due to migration or field evaporation of material into the gap which reportedly occurs at field strengths of 10 MV cm -1 [59] . This would correspond to an applied voltage of ~10 V and has been achieved in other cases where starting nanogap electrodes are on the same scale as those used here by applying a 10 V pulse [34], [53] or several sweeps between ±10 V [60]. Thus regardless of the mechanism, the forming step should be fairly similar.…”

“…Understanding the nature of the switching is important in determining the best forming step to employ. Naitoh et al [53] , who in 2006 first reported resistive switching in empty metal nanogap systems, argued the switching behaviour is not due to the formation of conductive channels, but rather changes in the physical nanogap dimensions. At a low voltage (+3.5 V) field evaporation with electrostatic attraction or field-induced metal migration were said to be candidates for decrease in nanogap size.…”

“…The differences in the HRS and LRS were then supposed to be due to tunneling current at different scales. To this end there is significant evidence that the reported nanogap switching behaviour is due to tunnelling current and a change in gap size, namely the temperature independence of the current, multilevel switching, [53] dependence of switching on the electrode material, [41] and independence of the switching behaviour on substrate material [54]. However, there is also significant evidence that switching can be due to a breakdown in the dielectric substrate (often SiO2), such as an independence of switching on electrode material [33], evidence of damage to the substrate [55], and direct imaging of filamentation taking place [28].…”

“…The only difference in the reported mechanisms is that for nanogap dimension change due to material migration switching, a sweep about the set voltage (e.g. +10 V → -1 V, [54] or +9 V → + 3 V [53] ) is employed, whereas for oxide switching, a pulse at the set voltage suffices [28], [31], [33], [55], [57].…”

4kb nonvolatile nanogap memory (NGpM) with 1 ns programming capability

“…The structures were integrated on a CMOS chip. The specially embedded measurement circuit revealed programming speed from a low resistance state to a high resistance state (from on to off state) to be 1 ns.Introduction One of the authors found that thin film metal electrodes with a gap less than 10 nm on an insulating substrate showed nonvolatile memory effect in vacuum [1]. Similar nanogap resistance change were widely observed for metals, such as Au, Pd, Pt, Ta [2], and even for Si [3] and carbon nanotubes [4] not only in vacuum but also in inert gases [10].…”