An Ion Scattering Study of Germanene Films on Au(111) and Al(111)

O. GRIZZI; E. CANTERO; E. MARTINEZ; L. SOLIS; Y. TONG; J. FUHR; M.L. MARTIARENA; E.A. SANCHEZ

Simposio; 10th International Symposium on Swift Heavy Ions in Matter &28th International Conference on Atomic Collisions in Solids; 2018

The scientific and technological advances that started with the production of graphene haveevolved rapidly to include research in other 2D materials from group-IV atoms. Thefabrication of silicene, stanene and more recently germanene is of great interest due to theproposed applications emerging from their novel electronic and structural properties. Themeasurement of Dirac-cones and other properties for these systems is promising, howeversome reservation remains in the scientific community because these elements, Ge inparticular, tend to form alloys with some of the used substrates or to diffuse within them.Among the different substrates proposed to grow germanene are Au(111) and Al(111) [1, 2].In the first case it was proposed that germanene films of up to several layers grow on top ofa mixed Ge-Au initial layer. For Al(111) it was proposed that one monolayer germanenegrows directly on top of the Al substrate. Testing these germanene films can be a difficulttask, with STM it was not possible to obtain atomic resolution and electron or photonspectroscopies have insufficient resolution to discriminate the top layer composition fromthe substrate contribution. Here ion scattering, particularly in the direct recoilingconfiguration, has the required surface resolution and is element andcrystallography sensitive, so it can contribute to a better understanding of these films [3]. Inthis work we describe a direct-recoil spectroscopy study for the growth of Ge on Au(111)and Al(111). We use a forward configuration with Ne, Ar and Kr projectiles in the energyrange of 3 ? 12 keV. TOF analysis allows detection of both ions and neutrals to avoiduncertainties due to charge exchange. Ne at high energy (10 -12 keV) has little focusingeffects and is then adequate to determine the top layer composition, while the strongshadowing for heavier projectiles such as Ar or Kr at lower energies (around 4 keV)provides information about the crystallography and the unambiguous presence of substrateatoms within the assumed pure germanene layer. The work is completed with the use ofSTM, LEED and DFT calculations providing further information about the symmetry andcrystallography of the films. AcknowledgementWe acknowledge funding from CONICET (PIP2015 112), Univ. Cuyo (06/C517) and theLIFAN cooperation program.References1. M.E. Dávila, et al, Scientific Reports 20714, Nature, 20162. M. Derivaz, et al, Nanoletters 15, 2510, 20153. E.D. Cantero, et al, Phys. Chem. Chem. Phys. 2017,19, 18580.