Surface-segregated Si and Ge ultrathin films formed by Ag-induced layer exchange process

Abstract We have developed a new method of growing Si or Ge ultrathin films on a Ag(111) surface by using a Ag-induced layer exchange (ALEX) process toward the creation of 2D honeycomb sheets of Si and Ge, known as silicene and germanene, respectively. In the present paper, we clarify ALEX features, specifically the surface segregation of Si (or Ge) atoms from the underlying substrate, focusing on the annealing temperature and time. Hard X-ray photoelectron spectroscopy analyses demonstrate that surface-segregated Si (or Ge) exists on the Ag surfaces after the epitaxial growth of the Ag layer on Si(111) or Ge(111) substrates; the amount of segregated Si (or Ge) can be controlled by a subsequent annealing. Also, we find that the segregation of an ultrathin Si or Ge layer proceeds at an interface between Ag and the AlO x capping layer.