Growth of \u03b1-Sn on silicon by a reversed \u03b2-Sn to \u03b1-Sn phase transformation for quantum material integration

Abstract

α-Sn and SnGe alloys are attracting attention as a new family of topological quantum materials. However, bulk α-Sn is thermodynamically stable only below 13∘C. Moreover, scalable integration of α-Sn quantum materials and devices on silicon is hindered by their large lattice mismatch. Here, we grow compressively strained α-Sn doped with 2-4 at.% germanium on a native oxide layer on a silicon substrate at 300–500∘C. Growth is found to occur by a reversed β-Sn to α-Sn phase transformation without relying on epitaxy, with germanium-rich GeSn nanoclusters in the as-deposited material acting as seeds. The size of α-Sn microdots reaches up to 200 nm, which is approximately ten times larger than the upper size limit for α-Sn formation reported previously. Furthermore, the compressive strain makes it a candidate 3D topological Dirac semimetal with possible applications in spintronics. This process can be further optimized to achieve optically tunable SnGe quantum material and device integration on silicon.