Time-of-Flight Direct Recoil Spectrometry applied to the characterization of 2D Xene films

Abstract

The synthesis of Xenes (silicene, phosphorene, germanene, etc.) on surfaces has recently refocused into heavier elements (stanene, antimonene, plumbene and bismuthene) due to their stronger spin–orbit coupling. This effect leads to intriguing topological properties, as well as potential applications in electronics, photonics and spintronics devices. Time-of-Flight Direct Recoil Spectrometry (TOF-DRS) emerged as a very effective technique for the characterization of 2D Xenes films due to: (1) the high top-surface sensitivity resulting from shadowing and blocking effects in the ion trajectories, and (2) the low damage imparted to the surface. Herein we review recent studies from our group related to the characterization of Ge and Sb films at monolayer thickness on monocrystalline metallic surfaces (Al and Au). We discuss scattering details from the different systems which highlight key peculiarities of the adsorbate/substrate interplay, like the presence of distinct structural phases. In particular, TOF-DRS analysis, complemented by other standard surface techniques (AES, LEED, STM) and DFT calculations allows for determining the top-surface elemental composition, the crystallography, and the evolution of the phases with temperature.