Yoshihiko Kurui

One-by-One Introduction of Single Lattice Planes in a Bottlenecked Gold Contact during Stretching

We observed the structural and conductance evolution of bottleneck-shaped gold contacts with [111] and [100] axes ([111] and [100] contacts) simultaneously during stretching. The [111] and [100] contacts were elastically stretched until a single (111) or (100) lattice plane was introduced by plastic deformation. The conductance decreased gradually by about 0.5–0.8 G 0 in the elastic regime, and subsequently stepped down at the plastic deformation. Since the conductance values changed depending on the strain, they were not quantized. The conductance histograms displayed rather broad peaks due to the elastic regime. These peaks reflected the particular sequence of the mechanical deformation of the contacts, in strong contrast to the peaks of the [110] contacts, which reflected the quantization as reported previously. Below 10 G 0 , we found that the gold [111] and [100] contacts had five and three specific structures, respectively, in addition to a single-atom contact at 1 G 0 . We conclude that, for a bott...

One-by-One Evolution of Conductance Channel in Gold (110) Nanowires

Using a transmission electron microscope combined with a scanning tunneling microscope, the relationship between structure and conductance of gold nanowires with axis along the [110] direction is investigated. The conductance histogram shows several high peaks and some subsidiary ones among them. The high peaks correspond to stable gold nanowires with a hexagonal cross section. The conductance peaks including the subsidiary peaks almost appear at integral multiples of the conductance quantum, G 0 (=2 e 2 / h ), which is a direct evidence that these peaks are due to one-by-one evolution of conductance channel.

In-Situ Observation of the Fabrication Process of a Single Shell Carbon Fullerene Nano-Contact Using Transmission Electron Microscope–Scanning Tunneling Microscope

A single shell carbon fullerene (SSF) was fabricated from an amorphous carbon agglomerate (a-C agglomerate) suspended between two gold electrodes. As the applied bias voltage to the a-C agglomerate was increased using a transmission electron microscope–scanning tunneling microscope (TEM–STM) system, the transformation into the SSF via a glassy carbon was observed. It was found that the SSF transformation occurred above the bias voltage of 0.6 V without a prominent loss of the number of carbon atoms. The size of the SSFs ranged from C60 to C620 having Ih or I symmetry.

Conductance Measurement of a Single Carbon Fullerene Suspended between Two Gold (111) Facets

We succeeded in sandwiching a single carbon fullerene between two (111) facets and measured the conductance at room temperature using a transmission electron microscope combined with a scanning tunneling microscope. The carbon fullerene prevented to move around at the gap when it was slightly compressed between two facets. In this condition, the C80 and C140 fullerenes had the values of 0.53 and 0.62G0 (=2e2/h), respectively, and sometime showed stepwise conductance change due to rotation. Since current–voltage characteristics showed metallic behavior for the C140 fullerene, the single carbon fullerene is thought to have metallic bonds to gold (111) surface under a slight compression, resulting in keeping the same adsorption site.

Controlling Quantized Steps in Conductance of Gold Zigzag Nanowires

We demonstrate that a gold zigzag nanowire changes conductance stepwise between 1 and 2G0 (=2e2/h, e is the elementary charge and h is Planck constant) upon slight stretching or compression at room temperature by a scanning tunneling microscope combined with a transmission electron microscope. The conductance change from 2 to 1G0 and vice versa occurred around the critical atomic distance of 0.32 nm, which is in agreement with theoretical calculations.

Conductance quantization of gold nanowires as a ballistic conductor

Electron transport in gold nanowires is studied by transmission electron microscopy (TEM) simultaneously with conductance measurement by using a scanning tunneling tip as an electrode. Conductance evolution while thinning of a gold nanowire shows sequential steps until it breaks after forming a single atomic chain. The step heights coincide the quantum unit, G0 = 2e2/h = (12.9kΩ)−1, except a little deviation due to multiple reflection. Gold nanowires fabricated in the ≪110≫ orientation can elongate to a several nanometer in length, and show linear current—voltage relation even for the bias voltage of 0.2V. Gold nanowires, thus, behave as a ballistic conductor, and their conductance is quantized to carry current, 1µA per single atomic chain at the bias voltage of 13mV.

Direct Observation of a Single Carbon Fullerene Transfer

We directly observed the transfer of a single 1.1-nm-diameter carbon fullerene between two gold electrodes separated by about 1.8 nm by applying a bias voltage of 0.6 V. The conductance showed sharp spikes of the order of 10-1G0 (=2e2/h) at the moment of transfer, which was on the order of those obtained when the fullerene bridged the two electrodes. No such transfer was observed at 0.1 V. We believe that the fullerene transfers at the moment when it has expanded, due to polarization, to the extent that it bridges the two electrodes under a high electric field.