Growth of Topological Materials from the 2D to the 3D Level: the Case of Xenes and Ditellurides

Two-dimensional (2D) materials offer intriguing opportunities to engineer and realize non-trivial topological states in condensed matter at the nanoscale [1]. For instance, 2D topological insulators, also known as quantum spin Hall insulators, are expected to take place in nano ribbons of Xenes, i.e. graphene-like 2D elementary materials, and single layers of transition metal ditellurides. Furthermore either kinds of materials display non-trivial Weyl or Dirac topological features in their three dimensional forms under appropriate lattice structures thus making it possible to tune the topological phase by dimensional variation [2]. Here we will address the two cases from the point of view of the production schemes. On one hand, Xene generations will be presented starting from the IV column of the periodic table (e.g., silicene, germanene, and stanene), up to more recent members from other columns in the periodic table (e.g. tellurene and/or bismuthene) [3]. We will pay attention to the epitaxial methodologies and configurational details with focus on heavier Xenes like stanene as more compelling candidate to display 2D topological properties. On the other hand, we will address ditellurides like MoTe₂ by discerning the best chemical vapour deposition schemes allowing for the isolation of the single 1T’ phase as precursor of non-trivial topological states [4]. We will also consider mixed 2D materials in heterostructures with the aim to stabilise the topological character of the individual components out of possible interactions with the host substrate [5]. In this scenario, we will devise technology-enabling processing schemes towards integration in device platforms [6]. Acknowledgement: funding from H2020 ERC-COG grant n. 772261 “XFab”.<br/>[1] A. Molle et al, <i>Nature Mater.</i> (2017) 16, 163.<br/>[2] S. Lupi and A. Molle, <i>Appl. </i><i>Mater. Today</i> (2020) 20, 100732.<br/>[3] C. Grazianetti et al, <i>Phys. </i><i>Stat. Sol. RRL </i>(2019), 14, 1900439.<br/>[4] C. Martella et al, Cryst. Growth Design (2021) 21, 2970.<br/>[5] D. S. Dhungana et al, <i>Adv. Funct. Mater.</i> (2021) 23, 2102797.<br/>[6] C. Martella, et al, <i>Adv. </i><i>Funct. Mater.</i> (2020) 30, 2004546.