A ferromagnetic insulating substrate for the epitaxial growth of topological insulators

Cr2Ge2Te6 is proposed as an insulating ferromagnetic substrate for the growth of tetradymite-type topological insulators, based on a refined characterization of its transport, magnetic, optical, and calculated electronic properties. It is found to be a soft ferromagnet with no visible magnetic domains over relatively large length scales and to be highly insulating with an indirect band gap and low carrier concentration. Further we present the fabrication of Bi2Te3-Cr2Ge2Te6 heterostructure samples by chemical vapor deposition and show that crystals of the two phases are oriented such that the hexagonal Te planes are aligned at their interfaces. (C) 2013 AIP Publishing LLC.