The team from the University of Basel and the French German Research Institute St. Louis (ISL) investigated diamond crystals of the size of only five nanometers (five millionths millimeter) using scanning tunneling microscopy and atomic force microscopy. The physicists then identified the atomic structure of the surface and observed crystalline, hexagonal carbon facets as well as graphitic reconstructions. In doing so, they discovered extra currents at specific voltages when the crystals were illuminated by green light.

These extra currents are related to the presence of defects in the carbon lattice of diamonds, so called Nitrogen-vacancy centers (NV-centers) that are optically active. These centers are promising candidates for future applications in quantum information processing systems, spin-magnetometry sensors or single photon sources. Their identification in the range of less than ten nanometers would have been very difficult with conventional methods, which is why the scientists applied a combination of different methods.

�With this study, we are able to show that it is possible to prove, with high resolution, the presence of optical centers in single nanodiamonds�, says Prof. Ernst Meyer of the Department of Physics at the University of Basel. In the future, NV-centers could be used in quantum computers that work much more efficiently than conventional computers.