Nanoscale grid based positioning system for miniature instrumented robots

To position an autonomous wireless robot (NanoWalker) over a sample´s single atom so it can be imaged or manipulated, a scanning tunnelling microscope (STM) is to be mounted on the robot itself. To do so a custom-built positioning system is developed. This requires the use of two sub-systems. The first to provide coarse positioning of the mobile unit in the micrometer range over a sample. To enable sub-micron range positioning of the NanoWalker, a second system is developed. Two different concepts are described. The first regards the usage of a tridimensional binary code to identify a single square. The second uses a variable-width line grid to uniquely characterize every intersection within the working surface. Many materials are considered, and the present work focuses on the results obtained on a highly oriented pyrolytic graphite (HOPG) sample. A preliminary screening of the machining techniques available suggested the use of focused ion beam (FIB); other techniques are also considered. Conclusions are drawn upon STM imaging.