Scientists at NIST have made significant progress in understanding the behavior of atoms on a crystal surface. Using a custom-built, cryogenic scanning tunneling microscope (STM), researchers were able to move a single atom in a small molecule back and forth between two positions on a crystal surface. This achievement is a crucial step toward building an “atomic switch” that can turn electrical signals on and off in nanoscale devices.
The team used a molecular chain of one cobalt atom and several copper atoms set upon a surface of copper atoms, which was constructed atom by atom using the STM in an atom manipulation mode. The STM was then used to shoot electrons at the molecular chain, and its effect on the switching motion of the cobalt atom was measured. The researchers also developed a “tunneling noise spectroscopy” technique to determine how long the atom stays in one place.
The scientists analyzed the atom switching rate as changes occurred in the STM voltage and in the current between the STM tip and surface. Above a threshold voltage of about 15-20 millivolts, the probability for switching per electron was constant, indicating that the electrons contain sufficient energy to move the cobalt atom. Higher currents resulted in faster switching, and the data suggested that a single electron boosts the molecule above a critical energy level, allowing a key bond to break so the cobalt atom can switch positions.
The work has significant implications for the development of new classes of electronic and magnetic devices constructed atom by atom. The findings also raise the possibility that molecular orbital analysis may be used to guide the design and control of single atom manipulation in nanostructures. The research was supported in part by the Office of Naval Research, and it demonstrates NIST’s commitment to advancing measurement science, standards, and technology in ways that enhance economic security and improve quality of life.
Keywords: Atom, Switching, Electron, Tunneling, Nanostructures
