Making Mn Substitutional Impurities in InAs using a Scanning Tunneling Microscope

Abstract

We describe in detail a new atom-by-atom exchange manipulation technique using a scanning tunneling microscope probe. As-deposited Mn adatoms (Mnad) are exchanged one-by-one with surface In atoms (Insu) to create a Mn surface-substitutional (MnIn) and an exchanged In adatom (Inad) by an electron tunneling induced reaction Mnad + Insu→MnIn + Inad on the InAs(110) surface. The Mn and In atom exchange process occurs when a negative applied tunneling potential to the InAs substrate exceeds a threshold of approximately -0.6 V. In combination with density-functional theory (DFT) and high resolution STM imaging, we have identified the reaction pathway for the Mn and In atom exchange. As the two atoms are exchanged, an energy barrier of 0.3 eV is found from DFT calculations in qualitative agreement with the experimentally observed voltage thresholds.