Thermal evolution of Fe on Ge(1 1 1)-c(2 × 8) surface and the effect of (√3 × √3)R30° Ag-Ge buffer layer

Using scanning tunneling microscopy, two systems of Fe deposition on clean Ge(1 1 1)-c(2 × 8) surface and surfaces with a (√3× √3)R30° Ag-Ge buffer layer were compared. Complex surface alloy structures were easily formed on Fe/Ge systems through annealing at 300-650 K. On clean Ge(1 1 1) surfaces, similar surface morphology evolution was observed when two different amounts of Fe were deposited. To reduce the complexity, (√3× √3)R30° Ag-Ge interfaces were used as buffer layers. The growth morphologies differed in the presence and absence of the buffer layers. During annealing at 570 K, (2 × 2) reconstruction platform islands were formed in the Fe-Ge system, which transformed to three-dimensional (3D) islands at 640 K. With Ag buffer layer, only nanoparticle growth occurred and 3D islands were formed early at 570 K. Generally, √19 ring clusters increased to break the order c(2 × 8) reconstruction by increasing the temperature and disappeared at 640 K in a Fe-Ge system, but only √7 ring clusters appeared at 390 K with (√3×√3)R30° Ag-Ge buffer layer.