Paper detail

Changing the lattice position of a bistable single magnetic dopant in a semiconductor using a scanning tunneling microscope

We report a reversible and hysteretic change in the topography measured with a scanning tunneling microscope near a single Fe dopant in a GaAs surface when a small positive bias voltage is applied. First-principles calculations of the formation energy of a single Fe atom embedded in GaAs as a function of displacement from the substitutional site support the interpretation of a reversible lattice displacement of the Fe dopant. Our calculations indicate a second stable configuration for the Fe dopant within the lattice, characterized by a displacement along the [111] axis, accompanied by a change in atomic configuration symmetry about the Fe from four-fold to six-fold symmetry. The resulting atomic configurations are then used within a tight-binding calculation to determine the effect of a Fe position shift on the topography. These results expand the range of demonstrated local configurational changes induced electronically for dopants, and thus may be of use for sensitive control of dopant properties and dopant-dopant interactions.