The work has its roots in the 1981 development of the STM by IBM researchers Gerd Binnig and Heinrich Rohrer, work for which they later received a Nobel Prize. In an STM, an atomically narrow metal tip is placed in proximity to the sample and a bias applied. When the probe gets within a few angstroms of the sample surface, the electrons tunnel across the gap, establishing a tunneling current. The level of the current varies depending on the tip-to-sample separation; that data is processed to create three-dimensional images with sub-nanometer spatial resolution.
When the tip-to-sample distance shrinks further, the probe tip exerts sufficient force to overcome the bond of the atom with the substrate and the atom can be moved to a new position. The process requires a fiendish level of positioning control and thermal and vibration stabilization, as well as a great deal of skill. In 1989, IBM Fellow Don Eigler used the STM to position 35 xenon atoms to spell out the company’s name. The movie business could hardly be far behind.
The image above shows the sample being placed in its holding fixture prior to installation in the sample chamber. For this project, STM must be used in vacuum and cooled to -268° C before work begins, a process that can take days.