Single germanene phase formed by segregation through Al(111) thin films on Ge(111)
Junji Yuhara, Hiroaki MUTO, Masaaki Araidai, Masato Kobayashi, Akio Ohta, Seiichi Miyazaki, Sho‐ichi Takakura, Masashi Nakatake, G. Le Lay
Abstract
Abstract We have obtained single phase monolayer germanene on aluminum (111) thin films grown on a germanium (111) template by atomic segregation epitaxy, a preparation method differing from molecular beam epitaxy used in previous works. This 2 × 2 reconstructed germanene phase matching an Al(111)3 × 3 supercell has been prepared in large areas upon annealing at 430 °C. Detailed studies have been carried out using scanning tunneling microscopy (STM), low-energy electron diffraction, Auger electron spectroscopy, and synchrotron radiation photoemission spectroscopy. First-principles calculations based on the density function theory along with atomic-scale STM images reveal the atomic structure with one protruding Ge atom per 2 × 2 germanene supercell and a characteristic dispersing band originating from the germanene sheet slightly coupled to the first layer Al atoms underneath. Instead, upon annealing at lower temperatures, multi-phase regions comprise twisted germanene domains in correspondence with an Al(111)√7×√7 R ± 19.1° superstructure as obtained in previous studies.