Isolated indium atoms on copper surfaces: A perturbed γ-γ angular correlation study

Abstract

IIIIn hyperfine probe atoms with a concentration of about 10 −4 ML have been utilized as nuclear observers on various copper surfaces. These isolated IIIIn probe atoms are highly sensitive to the local atomic structure via the electric-field-gradient tensor acting at the probe nuclear site; this quantity has been detected using the perturbed γ — γ angular correlation (PAC) method. The experiments deal with the localization of indium on substitutional terrace sites for Cu(100), Cu(111) and Cu(110) surfaces. Step sites have been observed in addition on vicinal Cu(111) and from thermal conversion between different sites diffusion data have been deduced. The electric field gradient has been investigated on Cu(110) for IIIIn deposited at various depths from the surface, revealing the extreme short-range character of the electric field gradient. Finally depositions (few percent of a ML) of natural indium have allowed to study formation and thermal decomposition of In-In configurations on copper surfaces.