Transport Properties with Multiple Functions of Fe@C₆₀-GNR Single Molecule

Encouraged by the successful fabrication of C₆₀-GNR (GNR=graphene nanoribbon) single-molecule transistors in experiments, four Fe-containing derived double-layered devices of Fe@C₆₀-GNR are designed by employing different electrode linkages and their transport properties are investigated by using density functional theory (DFT) and nonequilibrium Green's function (NEGF) methods. Regardless of electrode connection, all these devices give rise to a smaller negative differential resistance (NDR) peak at V=0.2 and a higher peak at 1.2 V, suggesting their stable maneuverability as molecular devices and good candidates for developing on(off)-off(on)-on(off) current switches. The macroscopic NDR performance depends on the delocalization character and the crossing mechanism of the frontier orbitals. The peak-to-valley current ratios (R_max) range from 454 to 2737, determined by the electrode linkage. Such a large R_max-value is necessary for developing dynamic random-access memory (DRAM) cells. Encapsulating the Fe atom inside C₆₀ not only improves the conductivity but also introduces the spin-polarized transport property. The spin-filtering efficiency (SFE) of almost all devices oscillates up and down in response to the bias voltage, indicating the possibility of designing on(off)-off(on)-on(off) spin switches and up-down spin switches. All these fascinating properties provide an important clue for designing similar molecular devices with multiple functions by trapping magnetic transition metal atoms inside fullerenes.