Fullerene has been expected to realize next generation nanoelectronics as a key element. However, although single-fullerene switch operation using scanning tunneling microscope (STM) has been developed, the structural architecture with electrodes is still needed to make progress as devices. Because the fullerenes are smaller than 1.0 nm, which is suitable for the STM approach, the subnanometer size is still too small, even with the latest device electrode fabrication techniques. Here we present the principle experiment on a self-assembling fullerene nanowire to drive single-fullerene switch. A fullerene C60-nanowire (C60NW), which was synthesized at a liquid–liquid interface, exhibited negative differential resistance (NDR) and two-state resistance switching generated by local polymerization and depolymerization among the C60 molecules. A C60NW was electrically characterized after a preset treatment to induce C60NW conductivity by electron-beam (EB) irradiation to form an initial conduction path. A current though the C60NW increased more than 100-fold after the preset treatment, whereas an as-grown C60NW exhibited a nanoampere-level current under a 20 V bias voltage. The current–voltage characteristics showed a nonlinear current increase and NDR, leading to reproducible two-state resistance switching under bias-voltage modulation. The nonlinear current increase, the NDR, and the resistance switching are explained by local energy control of the current-induced connection and disconnection of C60 molecules, leading to tunneling current modulation toward a single element of C60 in a nanomaterial switching function.

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.

Fullerenes, which are spherical molecules composed entirely of carbon, have attractive homogeneous shapes at subnanometer sizes and inherent physical and chemical properties that make them promising for use in nanoelectronics. In addition, fullerenes can be chemically functionalized with substitutional elements, which have been incorporated into devices to substantially improve their transport properties. The chemically functionalized fullerenes are known as fullerene derivatives. Using the chemically functionalized fullerene pyrrolidine tris-acid (CPTA), we developed a new device fabrication scheme for a fullerene resistance-switching element generated by the polymerization and depolymerization of C 60 polymer strings. To take advantage of the CPTA property, whereby it forms strong interactions with the surface of a substrate by strengthening the chemical bonds, a uniform thin CPTA film was spin-coated, and conductive fullerene polymerization was subsequently stimulated by a designed scan with an electron beam lithography (EBL) preset. The polymerized channel showed negative differential resistance in its current−voltage characteristics and performed twostate resistance switching, indicating that the polymerization and depolymerization of the C 60 polymer strings were alternatively controlled according to the external voltage input. EBL fabrication with solution-based nanomaterial coating has the potential of a bottom-up scheme for nanoelectronics, allowing for the design of intrinsic material properties.

Electromechanical switching in fullerene C60 nanochains, introduced in the device as a C60 pyrrolidine tris-acid (CPTA) film, was realized in nanogap electrodes with ∼20 nm separation. Unlike microscale C60 channels, a conductive C60 chain spontaneously formed in the nanogap without electron beam irradiation. The initial current flow was likely due to electron hopping through the CPTA molecules. A higher voltage generated a nonlinear current and caused a rapid current step to drastically generate a large current flow. A further high current generated a sudden current reduction recognized as the negative differential resistance, suggesting a resistance state change from a low state to a high state. At the high-resistance state, a step-like current increase changed the nanochain conduction to the low-resistance state. The high- to low-resistance state switching was reproducible, and a sequential input voltage executed a binary resistance switching operation at room temperature. From the switching voltage and current values, the switching energy for the C60 chain in the nanogap was estimated to be approximately several milliwatts, most probably caused by the polymerization and depolymerization of the conductive C60 chain.