Four-probe measurements with a three-probe scanning tunneling microscope.

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips.

Indications of field-directing and self-templating effects on the formation of organic lines on silicon.

It has previously been shown that multimolecular organic nanostructures form on H-Si(100)-2×1 via a radical mediated growth process. In this mechanism, growth begins through the addition of a molecule to a silicon surface dangling bond, followed by the abstraction of a neighboring H atom and generation of a new dangling bond on the neighboring site. Nanostructures formed by this mechanism grow along one edge of a dimer row.

Self-directed growth of contiguous perpendicular molecular lines on H-Si(100) surfaces.

Future nanoscale integrated circuits will require the realization of interconnections using molecular-scale nanostructures; a practical fabrication scheme would need to be largely self-assembling and operate on a large number of like structures in parallel. The self-directed growth of organic molecules on hydrogen-terminated silicon(100) [H-Si(100)] offers a simple method of realizing one-dimensional molecular lines. In this work, we introduce the ability to change the growth direction and form more complex, contiguous shapes.

Field regulation of single-molecule conductivity by a charged surface atom.

Electrical transport through molecules has been much studied since it was proposed that individual molecules might behave like basic electronic devices, and intriguing single-molecule electronic effects have been demonstrated. But because transport properties are sensitive to structural variations on the atomic scale, further progress calls for detailed knowledge of how the functional properties of molecules depend on structural features. The characterization of two-terminal structures has become increasingly robust and reproducible, and for some systems detailed structural characterization of molecules on electrodes or insulators is available.