Local detection of nitrogen-vacancy centers in a nanodiamond monolayer.

Nitrogen-vacancy defect centers (NV) contained in nanodiamonds (NDs) are a promising candidate in quantum information processing and single photon sources due to the capability of controlling their assembly on various surfaces. However, their detection with traditional optical techniques becomes challenging when probing high NV densities at the nanometer scale. Here, we combine scanning probe techniques to characterize in a monolayer the structural and electronic properties of bucky-diamonds with sizes below 10 nm. We further observe by light-assisted Kelvin- and scanning tunneling spectroscopy a clear signature of negatively charged subsurface NV centers in NDs at the nanoscale where conventional techniques are limited.

Directed rotations of single porphyrin molecules controlled by localized force spectroscopy.

Directed molecular repositioning is a key step toward the build up of molecular machines. To artificially generate and control the motion of molecules on a surface, excitations by light, chemical, or electrical energy have been demonstrated. Here, the application of local mechanical forces is implemented to achieve directed rotations of molecules. Three-dimensional force spectroscopy with sub-Ångström precision is used to characterize porphyrin derivatives with peripheral carbonitrile groups. Extremely small areas on these molecules (≈ 100 × 100 pm(2)) are revealed which can be used to control rotations. In response to the local mechanical forces, the molecular structure elastically deforms and then changes its conformation, which leads to its rotation. Depending on the selection of one of four submolecular areas, the molecule is either rotated clockwise or counterclockwise.

Atomic-scale mechanical properties of orientated C60 molecules revealed by noncontact atomic force microscopy.

In this work, the mechanical properties of C(60) molecules adsorbed on Cu(111) are measured by tuning-fork-based noncontact atomic force microscopy (nc-AFM) and spectroscopy at cryogenic conditions. Site-specific tip-sample force variations are detected above the buckyball structure. Moreover, high-resolution images obtained by nc-AFM show the chemical structure of this molecule and describes unambiguously its orientations on the surface.