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A combined UHV-EM and STM has enabled direct observations of nano-phenomena and products at the gap of the STM (and other probe microscopes) and sample surfaces at millisecond and meV resolution.
Thin gold wires with a helical structure were fabricated within the TEM-STM chamber. The finest one of very straight, self-organized wires had a thickness of 3 atoms, or 0.6 nanometers. Experiments verified a 7-fold helical wire strand for gold. The helical structure exists because it requires no crystal symmetry.
A single strand of gold atoms was first observed to exist suspended in free space between electrodes with an atomic spacing of 4 Åon average, extremely long compared to the nearest-neighbor distance, 2.9 Åin crystalline gold. No theory has explained this 4 Å Only a new physical principle might give a satisfactory explanation for this low-dimensional, finite particle system.
Quantum point contacts (QPCs) were prepared with a STM geometry in the TEM-STM. The conductance of a metal QPC could be simultaneously imaged using the TEM, allowing direct observations of electron transport and structure together. About 100 nm long gold strands formed one side of a chain of gold atoms suspended between two electrodes. It was possible to verify that the conductance of a single strand of atoms is 2e2/h, and that of a double strand is twice that, showing that equipartition holds for electron transport in these quantum systems. The TEM-STM system has allowed a verification of modern ALCHEMY: insullator-type gold nanowires from metallic gold could be made.
Nano-materials, as surface-induced new material phases, are now becoming possible. These new material phases would be adapted and applied for the sciences and technologies of the 21st century.
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