In this work, we demonstrate, for the first time, the capability of dynamic force microscopy (DFM) for the manipulation of individual atoms at surfaces. To do so, Yoshiaki Sugimoto and Shinji Hirayama created the nanostructures depicted on the right (representing the symbol of the Tin element) by manipulating Sn atoms (yellow protrusions) embedded in the surface plane of a Ge(111)-c(2x8) semiconductor surface. They spent more than 9 hours in a row moving atoms (the total experiment took about 12 hours) under an increasing stress, because just a little mistake operating the microscope could crash the AFM tip over the nanostrutures and destroy all the work. They performed more than 120 single-atom manipulations to arrange these Sn atoms and clean the surrounding area. You can download a movie showing the whole construction process from here (nmat1297s3.mov). There is more information about the experimental evidences that show us the way to succeed in achieving this feat in the paper: N. Oyabu et al., Nanotechnology 16, S112 (2005).
Another important result reported in this work is that these artificial nanoestructures were created at room temperature, remaining stable at the surface for a long period of time (more than a day). Before this work, it has been only possible to create similar artificial nanoestructures manipulating individual atoms or molecules using scanning tunneling microscopy (STM) at cryogenic temperatures (of the order of 4 to 10 K, that is -269 to -263 °C). The characteristic that makes it possible to manipulate these Sn atoms at room temperature, and give such stability to these nanostructures, is that these Sn atoms are not adsorbed over the surface but embedded in the surface outermost atomic layer.
The ability to manipulate atoms embedded in the plane of a semiconductor surface using DFM holds substantial promise in semiconductor technology, for instance, specific dopants of different nature could be arrange at predetermined positions along the gates of nanometric transistors to enhance performance of the device [see for example, T. Shinada et al., Nature 437 1128 (2005)].