Weak coupling of buckled germanene with high Fermi velocity on semiconducting Cu2Te

Abstract

Despite its promise, growing a quasi-freestanding monolayer of germanene with Dirac cone signature remains a significant attention. Synthesizing germanene on semiconductor surfaces is highly desirable to preserve its linear energy dispersion near the K points, which has been experimentally challenging. Here, we report the molecular beam epitaxy of monolayer germanene on semiconducting Cu2Te supported by Cu(111). Scanning tunneling microscopy/spectroscopy (STM) revealed a low-buckled honeycomb lattice of germanene, exhibiting an intrinsic Dirac cone at the K point. By combining STM measurements with theoretical simulations, we confirm that germanene atoms occupy threefold hollow sites on Cu2Te via van der Waals interaction. Remarkably, by dI/dV spectra fitting, we find the prepared germanene owns the Fermi velocity of (6.9 ± 0.1) × 105 m/s, which is slightly higher than the density functional theory calculated 4.6 × 105 m/s with considering the dielectric constant of the underlying Cu2Te, implying the weak coupling of germanene with the substrate. This work provides a platform for further exploring the ballistic charge transport properties of germanene with a Dirac cone.