Biomedical subjects

Oscar Custance

Publications and source records attributed to Oscar Custance.

4 recordsLinked to original sources

PubMed2006

Single atomic contact adhesion and dissipation in dynamic force microscopy.

By combining dynamic force microscopy experiments and first-principles calculations, we have studied the adhesion associated with a single atomic contact between a nanoasperity--the tip apex--and a semiconductor surface--the Ge(111)-c(2 x 8). The nanoasperity's termination has been atomically characterized by extensive comparisons of the measured short-range force at specific sites with the chemical forces calculated using many atomic models that vary in structure, composition, and relative orientation with respect to the surface. This thorough characterization has allowed us to explain the dissipation signal observed in atomic-resolution images and force spectroscopic measurements, as well as to identify a dissipation channel and the associated atomic processes.

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PubMed2005

Atom inlays performed at room temperature using atomic force microscopy.

The ability to manipulate single atoms and molecules laterally for creating artificial structures on surfaces is driving us closer to the ultimate limit of two-dimensional nanoengineering. However, experiments involving this level of manipulation have been performed only at cryogenic temperatures. Scanning tunnelling microscopy has proved, so far, to be a unique tool with all the necessary capabilities for laterally pushing, pulling or sliding single atoms and molecules, and arranging them on a surface at will. Here we demonstrate, for the first time, that it is possible to perform well-controlled lateral manipulations of single atoms using near-contact atomic force microscopy even at room temperature. We report the creation of 'atom inlays', that is, artificial atomic patterns formed from a few embedded atoms in the plane of a surface. At room temperature, such atomic structures remain stable on the surface for relatively long periods of time.

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PubMed2004

Atom-selective imaging and mechanical atom manipulation using the non-contact atomic force microscope.

We succeeded in distinguishing between oxygen and silicon atoms on an oxygen-adsorbed Si(111)7 x 7 surface, and also distinguished between silicon and tin atoms on Si(111)7 x 7-Sn intermixed and Si(111) square root(3) x square root(3)-Sn mosaic-phase surfaces using non-contact atomic force microscopy (NC-AFM) at room temperature. Atom species of individual atoms are specified from the number of each atom in NC-AFM images, the tip-sample distance dependence of NC-AFM images and/or the surface distribution of each atom. Further, based on the NC-AFM method but using soft nanoindentation, we achieved two kinds of mechanical vertical manipulation of individual atoms: removal of a selected Si adatom and deposition of a Si atom into a selected Si adatom vacancy on the Si(111)7 x 7 surface at 78 K. Here, we carefully and slowly indented a Si atom on top of a clean Si tip apex onto a predetermined Si adatom to remove the targeted Si adatom and onto a predetermined Si adatom vacancy to deposit a Si atom, i.e. to repair the targeted Si adatom vacancy. By combining the atom-selective imaging method with two kinds of mechanical atom manipulation, i.e. by picking up a selected atom species and by depositing that atom one by one at the assigned site, we hope to construct nanomaterials and nanodevices made from more than two kinds of atom species in the near future.

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PubMed2003

Mechanical vertical manipulation of selected single atoms by soft nanoindentation using near contact atomic force microscopy.

A near contact atomic force microscope operated at low-temperature is used for vertical manipulation of selected single atoms from the Si(111)-(7 x 7) surface. The strong repulsive short-range chemical force interaction between the closest atoms of both tip apex and surface during a soft nanoindentation leads to the removal of a selected silicon atom from its equilibrium position at the surface without additional perturbation of the (7 x 7) unit cell. Deposition of a single atom on a created vacancy at the surface is achieved as well. These manipulation processes are purely mechanical, since neither bias voltage nor voltage pulse is applied between probe and sample. Differences in the mechanical response of the two nonequivalent adatoms of the Si(111)-(7 x 7) with the load applied is also detected.

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