Quantum Materials - 20

Abstract

A fullerene nano-chain connected with metallic junction on silicon substrates has been realized using a derivative of fullerene with a carboxy group “Pyrrolidine Tris Acid (CPTA)” [1,2]. This fullerene nano-chain showed a resistance switch at room temperature. The resistance switch in nano-chain junction is not limited to C₆₀ but should also occur in C₇₀ fullerenes. In this research, we focused on the high electron-accepting ability of ₇₀ and fabricated a fullerene resistive element using a C₇₀ derivative, [6,6]-Phenyl C71 butyric acid methyl ester (PC71BM) and evaluated its switching behavior.
Figure 1 shows a schematic of the PC71BM device. Conductivity measurements were performed at room temperature in a vacuum environment (<1.0×10-2 Pa), and when the voltage was applied to the devices, resistance switching was observed in the PC71BM devices as in the CPTA devices. Two resistance states of “High Resistance State (HRS)” and “Low Resistance State (LRS)” are switched by the application of voltage. Figure 2 (a) shows a typical I–V characteristic as set process, where the current shows transitions from LRS to LRS when voltage is applied. On the other hand, Fig. 2 (b) shows a typical I–V characteristic as reset process, where an increase in the applied voltage causes a sudden decrease, which is recognized as negative differential resistance (NDR) change from LRS to HRS. From distribution plots of turn-on and NDR peak voltages (Figs. 2(c) and 2(d)), average voltages of 2.9 V for turn-on voltage and 3.3 V for NDR peak were obtained. The switching voltages of these C₇₀-based PC71BMs tend to operate at lower voltages than those of the C₆₀-based CPTAs investigated so far.