Indexed on: 25 Jan '16Published on: 25 Jan '16Published in: Physics - Mesoscopic Systems and Quantum Hall Effect
Three-dimensional topological insulator (3D-TI) high-quality ultrathin films of Bi2-xSbxTe3-ySey (BSTS), ranging from a few quintuple to several hundreds of layers, are epitaxlally grown on mica in large-area (1 cm2) via catalyst-free vapor phase deposition by employing a three-zone furnace under 0.1 Pa pressure. These films can nondestructively be exfoliated using 2.38 % tetra-methyl ammonium hydroxide water solution followed by rinse with acetone and transferred to various kinds of substrates as desired. The ultrathin films thus prepared on SiO2/Si substrate well preserve insulating bulk conductivity and topologically protected nontrivial Dirac electronic surface states. High quality of the transferred films is confirmed by electrical transport measurements, where clear Shuvnikov-de Haas (SdH) quantum oscillations can be seen with high carrier mobility of 2500 and 5100 cm2V-1S-1 arising from top and bottom surfaces. A good ambipolar conduction resulting from the Dirac fermions on the topological surface states is demonstrated in a field effect transistor made on a BSTS thin film transferred to a SiO2/Si substrate. Both the feasible large area synthesis and the reliable film transfer process can promise that BSTS ultrathin films will pave a route to many applications of 3D-TIs.