Epitaxial Growth of Germanium Ultrathin Films on Ag(100) Thin Films on Ge(100) Substrates Prepared by Atomic Segregation Epitaxy

This study investigates the growth of germanene on an Ag(100) thin film on a Ge(100) substrate through germanium (Ge) segregation, using Auger electron spectroscopy, low‐energy electron diffraction (LEED), scanning tunneling microscopy (STM), and core‐level (CL) photoemission spectroscopy. A clean Ag(100) surface is obtained by annealing at 300 °C, and R45° spots are mainly seen in the LEED pattern after annealing at 370 °C. When annealed at 460 °C, a square‐shaped streak with a threefold Ag(100) periodicity appears in the LEED pattern, specifically the partially incommensurate (3 × n ) superstructure, where n is an arbitrary number. The STM images of the (3 × n ) superstructure reveal two domains rotated at 90°. After annealing at 540 °C, the LEED pattern displays an incommensurate sixfold symmetry (1.20 × 1.20) with a unit cell length of 0.40 nm. From angle‐resolved CL spectra, Ge atoms are found at the topmost surface of the Ag(100). CL spectra suggest that the chemical state is similar to that of germanene on Ag(111). These findings demonstrate the formation of a sixfold germanium atomic layer on Ag(100).