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

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 Lu₃N@C₈₀, a charge transfer of six electrons occurs between the endohedral fullerene Lu₃N and the C₈₀ cage. To investigate their electrical conduction, we synthesized Lu₃N@C₈₀ 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 Lu₃N@C₈₀ NW switching repetition could be explained as changing the position motion and bonding configuration of a key Lu₃N@C₈₀ bridging the conductive fullerene path.