Rhombic Coulomb diamonds in a single-electron transistor based on an Au nanoparticle chemically anchored at both ends

Coherent Resonant Electron Tunneling at 9 and 300 K through a 4.5 nm Long, Rigid, Planar Organic Molecular Wire

Organic molecular wires that operate stably at ambient temperatures are a necessary first step toward practical and useful molecular-scale electronic devices, which have thus far been hampered by many factors, including the structural and electron configurational instability of organic molecules. We report here that a single disulfanyl carbon-bridged oligo(phenylenevinylene) (COPV6) molecule embedded between thermally stable electroless Au-plated electrodes of a 4 nm nanogap undergoes coherent resonant tunneling at both 9 and 300 K and functions even after storage in air at room temperature. Such enormous stability is ascribed to the unique structural characteristics of COPV6, that is, rigidity, planarity, thermal stability, resistivity against oxidation and reduction, and an organic insulating sheath that protects the π-system. When sandwiched between the gaps without pinning, this molecule behaves as a Coulomb island with sequential single-electron tunneling at 9 K that disappears at 300 K while maintaining a stable electron flow.

Three-input gate logic circuits on chemically assembled single-electron transistors with organic and inorganic hybrid passivation layers

Single-electron transistors (SETs) are sub-10-nm scale electronic devices based on conductive Coulomb islands sandwiched between double-barrier tunneling barriers. Chemically assembled SETs with alkanethiol-protected Au nanoparticles show highly stable Coulomb diamonds and two-input logic operations. The combination of bottom-up and top-down processes used to form the passivation layer is vital for realizing multi-gate chemically assembled SET circuits, as this combination enables us to connect conventional complementary metal oxide semiconductor (CMOS) technologies via planar processes. Here, three-input gate exclusive-OR (XOR) logic operations are demonstrated in passivated chemically assembled SETs. The passivation layer is a hybrid bilayer of self-assembled monolayers (SAMs) and pulsed laser deposited (PLD) aluminum oxide (AlO[Formula: see text]), and top-gate electrodes were prepared on the hybrid passivation layers. Top and two-side-gated SETs showed clear Coulomb oscillation and diamonds for each of the three available gates, and three-input gate XOR logic operation was clearly demonstrated. These results show the potential of chemically assembled SETs to work as logic devices with multi-gate inputs using organic and inorganic hybrid passivation layers.

Molecular floating-gate single-electron transistor

We investigated reversible switching behaviors of a molecular floating-gate single-electron transistor (MFG-SET). The device consists of a gold nanoparticle-based SET and a few tetra-tert-butyl copper phthalocyanine (ttbCuPc) molecules; each nanoparticle (NP) functions as a Coulomb island. The ttbCuPc molecules function as photoreactive floating gates, which reversibly change the potential of the Coulomb island depending on the charge states induced in the ttbCuPc molecules by light irradiation or by externally applied voltages. We found that single-electron charging of ttbCuPc leads to a potential shift in the Coulomb island by more than half of its charging energy. The first induced device state was sufficiently stable; the retention time was more than a few hours without application of an external voltage. Moreover, the device exhibited an additional state when irradiated with 700 nm light, corresponding to doubly charged ttbCuPc. The life time of this additional state was several seconds, which is much shorter than that of the first induced state. These results clearly demonstrate an alternative method utilizing the unique functionality of the single molecule in nanoelectronics devices, and the potential application of MFG-SETs for investigating molecular charging phenomena.