Combined surface x-ray diffraction and density functional theory study of the germanene/Al(111)-(√7 x √7)R19.1° structure

Several studies have reported the possible growth of germanene on various metal surfaces. However, the exact structure of the layers formed upon evaporation at or above room temperature remains controversial. In particular, the layers obtained after Ge deposition on Al(111) have been either considered as honeycomb organization of Ge atoms on top of a nonreconstructed substrate, or as alloyed layers. Using quantitative measurements by surface x-ray diffraction compared to density functional theory calculations, we show that the (root 7 x root 7)R +/- 19.1 degrees reconstruction obtained after room temperature deposition is a mixed Ge-Al honeycomb layer, on top of an Al(111) plane, and not a pure germanene layer.