Stable Resistance Switching in Lu₃N@C₈₀ Nanowires Promoted by the Endohedral Effect: Implications for Single-Fullerene Motion Resistance Switching

Abstract

Fullerenes are spherical clusters composed entirely of carbon atoms with an inner space that can accommodate atoms or small molecules; when the inner space is occupied, the resultant materials are known as endohedral fullerenes. Because the caged component of endohedral fullerenes can modify the electronic state of the carbon cage, endohedral fullerenes can function as a designed tiny electronic unit. Some endohedral fullerenes have excess electrons on the carbon cage, and these electrons function as a charge source for electrical conduction. In addition, endohedral fullerenes exhibit enhanced chemical reactivity. In the endohedral fullerene Lu 3 N@C 80 , a charge transfer of six electrons occurs between the endohedral fullerene Lu 3 N and the C 80 cage. To investigate their electrical conduction, we synthesized Lu 3 N@C 80 nanowires (NWs) at a liquid−liquid interface and characterized them without subjecting them to the conduction preset associated with polymerization induced by irradiation with an electron beam or ultraviolet light. When current−voltage measurements were performed in a two-terminal configuration, the current increased with increasing voltage applied to the NW and then decreased after reaching the current maximum. This change in current is known as negative differential resistance (NDR). When a two-terminal voltage was applied to the NW with the observed NDR, the NW resistance showed switching behavior between a high-resistance state for the off state and a low-resistance state for the on state. Such resistive switching is expected as one of the elements of nanoelectronics. In particular, the two-terminal devices potentially realize single-fullerene motion resistive switching and nonvolatile memory. The temperature dependence of the on/off current ratio of the switching characteristic tended to increase with increasing measurement temperature as a consequence of fullerene coupling and the switching behavior induced by the applied current. These experimental analyses suggested that a stable Lu 3 N@C 80 NW switching repetition could be explained as changing the position motion and bonding configuration of a key Lu 3 N@C 80 bridging the conductive fullerene path.

Fullerene Nanostructure-Coated Channels Activated by Electron Beam Lithography for Resistance Switching

“…A voltage in I – V characteristics generated a current through the polymerization string, which stimulated thermal activation in conduction, and a further thermal heating effect by nonlinear current caused the polymerization string to conduct, and the current reached overcurrent. However, the overcurrent caused overheating and eventually prompted the polymerization bonding between C 60 –C 60 to be resolved. ,, The thermal bond disconnection of the C 60 –C 60 polymer caused a current drop, which manifested as the NDR effect. Because the current flow was blocked by a disconnected gap between C 60 –C 60 , a relatively large voltage could generate a current through the disconnected tunneling gap, which stimulated repolymerization and resulted in the formation of a C 60 –C 60 polymer connection and a lowering of the resistance to the LRS.…”

“…In the following, we describe two advantages of the EBL preset on the CPTA film over other types of fullerene channel switching. , A direct patterning of the CPTA film by the EBL, which was a one-step process for conduction channel activation, was effective in generating film conduction from the intrinsic insulator. Furthermore, an arbitrary design could improve the total device performance.…”

“…However, the overcurrent caused overheating and eventually prompted the polymerization bonding between C 60 −C 60 to be resolved. 25,35,42 The thermal bond disconnection of the C 60 −C 60 polymer caused a current drop, which manifested as the NDR effect. Because the current flow was blocked by a disconnected gap between C 60 −C 60 , a relatively large voltage could generate a current through the disconnected tunneling gap, which stimulated repolymerization and resulted in the formation of a C 60 −C 60 polymer connection and a lowering of the resistance to the LRS.…”

“…In accordance with this requirement, a resistive switching device using self-assembled fullerene C 60 nanowires (C 60 NW) has been demonstrated by Umeta et al Electrical switching operation was demonstrated using C 60 NWs, which can be grown at the liquid–liquid interface. − It is generally known that, although the as-grown C 60 NWs have low electrical conductivity, such conductivity is greatly improved by light or EB irradiation. , The current–voltage ( I – V ) characteristics of C 60 NWs irradiated by EB showed reproducible negative differential resistance (NDR). , Polymerization and depolymerization of the fullerenes were controlled by applying voltage, and two-state resistance switching was realized at room temperature. In addition, by using the intrinsic properties of Lu 3 N@C 80 nanowires, the as-grown Lu 3 N@C 80 nanowires were conductive and showed remarkably stable resistance switching operations . Despite the demonstrated switching, and regardless of the fullerene or the endohedral fullerene employed, it is difficult to adjust the NW length and diameter to a uniform size. − Because it is also known that control of the position of the NWs on the substrate is difficult, their position relative to the electrode was randomly located.…”

“…In addition, by using the intrinsic properties of Lu 3 N@C 80 nanowires, the as-grown Lu 3 N@C 80 nanowires were conductive and showed remarkably stable resistance switching operations. 42 Despite the demonstrated switching, and regardless of the fullerene or the endohedral fullerene employed, it is difficult to adjust the NW length and diameter to a uniform size. 43−45 Because it is also known that control of the position of the NWs on the substrate is difficult, their position relative to the electrode was randomly located.…”