Department of Physics, Graduate School of Science, Tohoku University , Sendai, 980-8578, Japan.
WPI Advanced Institute for Materials Research, Tohoku University , Sendai 980-8577, Japan.
Nano Lett. 2017 Apr 12;17(4):2354-2360. doi: 10.1021/acs.nanolett.6b05260. Epub 2017 Mar 27.
Uniform and large-area synthesis of bulk insulating ultrathin films is an important subject toward applications of a surface of three-dimensional topological insulators (3D-TIs) in various electronic devices. Here we report epitaxial growth of bulk insulating three-dimensional topological insulator (3D-TI) BiSbTeSe (BSTS) ultrathin films, ranging from a few quintuple to several hundreds of layers, on mica in a large-area (1 cm) via catalyst-free physical vapor deposition. These films can nondestructively be exfoliated using deionized water and transferred to various kinds of substrates as desired. The transferred BSTS thin films show good ambipolar characteristics as well as well-defined quantum oscillations arising from the topological surface states. The carrier mobility of 2500-5100 cm/(V s) is comparable to the high-quality bulk BSTS single crystal. Moreover, tunable electronic states from the massless to the massive Dirac fermion were observed with a decrease in the film thickness. 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.
大面积、均匀合成块状绝缘的超薄薄膜是表面三维拓扑绝缘体（3D-TI）在各种电子器件中应用的一个重要课题。本文通过无催化剂的物理气相沉积，在云母上大面积（1 厘米）外延生长了从几个五重到数百个单层的块状绝缘三维拓扑绝缘体（3D-TI）BiSbTeSe（BSTS）超薄薄膜。这些薄膜可以用去离子水无损剥落，并根据需要转移到各种基底上。转移的 BSTS 薄膜表现出良好的双极性特性以及源自拓扑表面态的清晰量子振荡。载流子迁移率为 2500-5100cm/（V s），与高质量的块状 BSTS 单晶相当。此外，随着薄膜厚度的减小，可以观察到从无质量到有质量的狄拉克费米子的可调谐电子态。可行的大面积合成和可靠的薄膜转移工艺可以保证 BSTS 超薄薄膜将为三维拓扑绝缘体的许多应用铺平道路。
