Cryogenic Temperature Growth of Sn Thin Films on Ferromagnetic Co(0001)

Topological electronic materials hold great promise for revolutionizing spintronics, owing to their topological protected, spin-polarized conduction edge or surface state. One of the key bottlenecks for the practical use of common binary and ternary topological insulator materials is the large defect concentration that leads to a high background carrier concentration. Elemental tin in its alpha-phase is a room temperature topological semimetal, which is intrinsically less prone to defect-related shortcomings. Recently, the growth of ultrathin alpha-Sn films on ferromagnetic Co surfaces has been achieved; however, thicker films are needed to reach the 3D topological Dirac semimetallic state. Here, the growth of alpha-Sn films on Co at cryogenic temperatures was explored. Very low-temperature growth holds the promise of suppressing undesired phases, alloying across the interfaces, as well as the formation of Sn pillars or hillocks. Nevertheless, the critical Sn layer thickness of approximate to 3 atomic layers, above which the film partially transforms into the undesired b-phase, remains the same as for room-temperature growth. From ferromagnetic resonance studies, and supported by electron microscopy, it can be concluded that for cryogenic Sn layer growth, the interface between Sn and Co remains sharp and the magnetic properties of the Co layer stay intact.

Automated summary

Topological electronic materials hold promise for spintronics revolution. Common topological insulator materials suffer from high defect concentration. Low-temperature growth of alpha-Sn films on Co preserve the sharp interface and magnetic properties of the Co layer.