Coexistence of strongly buckled germanene phases on Al(111)

TL;DR

This study investigates the structural and electronic properties of germanium layers on Al(111), revealing coexistence of different buckled germanene phases stabilized at high temperatures through combined experimental and theoretical methods.

Contribution

It demonstrates the formation of strongly buckled germanene phases on Al(111) with two stable orientations, supported by experimental STM and core-level spectroscopy and first-principles calculations.

Findings

Identification of (3×3) and (√7×√7)R±19.1° reconstructions.

Atomic model of a buckled (2×2) germanene layer consistent with experimental data.

Confirmation of two stable orientations of germanene on Al(111).

Abstract

We report a study of structural and electronic properties of a germanium layer on Al(111) using scanning tunneling microscopy (STM), low energy electron diffraction and core-level photoelectron spectroscopy. Experimental results show that a germanium layer can be formed at a relatively high substrate temperature showing either (3$\times$3) or ($\sqrt{7}$$\times$$\sqrt{7}$)R$\pm$19.1{\deg} reconstructions. First-principles calculations based on density functional theory suggest an atomic model consisting of a strongly buckled (2$\times$2) germanene layer, which is stable in two different orientations on Al(111). Simulated STM of both orientations fit nicely with experimental STM images and the Ge 3d core-level data decomposed into four components is consistent with the suggested model.