One factor limiting the scaling and
reproducibility of device elements in computer processors is the random
distribution of dopants in semiconductor nanostructures. To overcome this
obstacle for faster computing, new ways to position and address individual
dopants 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 properties of single magnetic dopants in GaAs using atomic
defects. Experiments were performed using a custom-built scanning tunneling
microscope operating at low temperature (7K) and in ultrahigh vacuum. The
electric field emanating from a charged As vacancy (VAs+) was used to tune the binding
energy and ionization state of single Mn dopants (i.e. MnGa). The vacancies could be
positioned with atomic precision by applying a voltage to the microscope tip.
These studies not only suggest a route for continued miniaturization of current
computing technology, but also contribute toward a fundamental understanding of
ferromagnetic semiconductors; a class of materials of interest for new
computing paradigms.
