MBE growth, Structural, morphological, and transport properties of (Bi_1−xSb_x)₂(Te_0.85Se_0.15)₃ quaternary thin films.

Topological insulators are a type of quantum material that have an insulating bulk but conductive surfaces. Among these, the three-dimensional group V-VI topological insulators Bi₂Te₃, Bi₂Se₃, and Sb₂Te₃ are of particular interest because their band structure features a single Dirac cone at the Γ point, and they are comparatively easier to grow on a variety of substrates through the van der Waals epitaxy. It is possible to tune the optical and transport properties of these binary materials by forming their ternary and quaternary alloys. In this work, we demonstrate how varying the concentrations of Sb affects the structural, morphological, and transport properties of (Bi_1−xSb_x)₂(Te_0.85Se_0.15)₃ quaternary thin films grown by molecular beam epitaxy. Additionally, we have demonstrated how a combination of x-ray diffraction and Raman measurement can be used to characterize the composition of these quaternaries without the use of time-consuming Rutherford backscattering measurements. Better control over the growth of these materials can be promising for the advancement of spintronic devices.