Spin coupling in Ag film growth on Sn/Ge(111)-[formula omitted

Abstract

Silver has been deposited on the Sn/Ge(111)-(3×3)-R30° surface at room temperature. The Ag growth and resulting surface morphology have been investigated using scanning tunneling microscopy. The first layer of silver forms an interface with domains of two different phases. One structure consists of short atomic rows with three-fold symmetry, oriented in the directions of the 3×3 surface. These rows are separated by a distance equal to 3 and are found to fit a 23×3 unit cell. The other phase is a 3×3 honeycomb structure, oriented in the Ge(111) 1 × 1 directions. Atomic structural models for the two interface phases are proposed, based on two different spin arrangements of the Sn/Ge(111)-3×3 surface. The results highlight the topological coupling of the two interface faces. Both interface structures are preserved with additional silver deposition. The second layer of Ag grows with a bulk-like lattice thickness on top of both interfaces. Low-energy electron diffraction on a mostly two layer Ag film reveals that it consists of domains where Ag grows in different orientations. These domains are rotated 30° with respect to each other, and thus mirror the symmetry directions of the two interfacial phases.