The ability to manipulate individual atoms and molecules using a scanning tunneling microscope (STM) has been crucial for the development of a vast array of atomic-scale devices and structures ranging from nanoscale motors and switches to quantum corrals. Molecular motors in particular have attracted considerable attention in view of their potential for assembly into complex nanoscale machines. Whereas the manipulated atoms or molecules are usually on top of a substrate, motors embedded in a lattice can be very beneficial for bottom-up construction, and may additionally be used to probe the influence of the lattice on the electronic properties of the host material. Here, we present the discovery of controlled manipulation of a rotor in Fe doped Bi 2 Se 3 . We find that the current into the rotor, which can be finely tuned with the voltage, drives omni-directional switching between three equivalent orientations, each of which can be frozen in at small bias voltage. Using current fluctuation measurements at 1 MHz and model simulations, we estimate that switching rates of hundreds of kHz for sub-nanoampere currents are achieved.

We report on the structural properties of highly B-doped silicon (up to 10 at.% of active doping) realised by nanosecond laser doping. The crystalline quality, lattice deformation and B distribution profile of the doped layer are investigated by Scanning Transmission Electron Microscopy followed by High-Angle Annular Dark Field contrast studies and Geometrical Phase Analysis, and compared to the results of Secondary Ions Mass Spectrometry and Hall measurements. When increasing the active B concentration above 4 at.%, the fully strained, perfectly crystalline, Si:B layer starts showing dislocations and stacking faults. These only disappear around 8 at.% when the Si:B layer is well accommodated to the substrate. With increasing B incorporation, an increasing number of small precipitates is observed, together with filaments with a higher active B concentration and stacking faults. At the highest concentrations studied, large precipitates form, related to the decrease of active B concentration. The structural information, defect type and concentration, and active B distribution are connected to the initial increase and subsequent gradual loss of superconductivity.

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