Multiple Charge States of Ag Atoms on Ultrathin NaCl Films

A combined study using density functional calculations and scanning tunneling microscopy experiments shows that individual silver adatoms on ultrathin sodium chloride films on copper surfaces are stable in three different charge states—neutral, negatively, and positively charged adatoms. The charge states of the individual adatoms were manipulated by voltage pulses. The key parameters determining the stability of various charge states are identified and discussed within a simple model.