An NSF Materials Research Science and Engineering Center (MRSEC)

1. Center for Emergent Materials The Ohio State University http://cem.osu.edu Atomic-sized bits Chris P. Hammel, Ohio State University Research Foundation, DMR 0820414 One factor limiting the scaling and reproducibility of device elements in computer processors is the random distribution of impurity atoms in semiconductor nanostructures. To overcome this obstacle for faster computing, new ways to position and address individual atoms are needed. Proposals for next-generation computing based on quantum variables such as electron spin also require the ability to address and control interactions between individual atoms. Researchers at Ohio State University’s Center for Emergent Materials have recently discovered a new method for controlling the charge state of single magnetic dopant atoms in GaAs. Experiments were performed using a custom-built scanning tunneling microscope operating at low temperature (7K) and in ultrahigh vacuum. The charge state of individual Mn atoms was switched by tuning the local electric field, which reflects both the bias voltage applied to the microscope tip, as well as its proximity. This switching produces a ring-like feature centered on the dopant atoms. The diameter of this ring depends on the total local electric field, due to both the tip, as well as nearby defects which may be charged. These studies help us envision future technologies where digital information is encoded in the charge state of an individual atom. Ionization rings around three Mn dopants in a GaAs crystal. For scale, columns of As atoms separated by 0.5 nm are visible in the image. Co Au Co D.H. Lee and J.A. Gupta, Nanoletters11, 2004 (2011) An NSF Materials Research Science and Engineering Center (MRSEC) Supported under Award Number DMR-0820414