Characterization of Copper (100) Surfaces by Isolated Indium Probe Atoms via the Electric Field Gradient

The electric quadrupole hyperfine interaction at Cu (100) surfaces has been detected at isolated ¹¹¹In probe atoms by use of the perturbed γγ angular correlation technique. The electric-field-gradient tensor at $T=295$ K was found to be axially symmetric with a strength of |Vzz|=1.0(2)×10¹⁸ V/cm² and the symmetry axis perpendicular to the (100) surface. A linear temperature dependence of the electric field gradient was observed. These findings support the assumption of highly symmetric surface sites as positions for the ¹¹¹In probes.