Synthesis of the 2D Ternary Topological Insulator Bi<sub>2‐x</sub>Sb<sub>x</sub>Se<sub>3</sub> with a Low Carrier Concentration and Ultrahigh Carrier Mobility
Muhammad Zeeshan Saeed, Zimei Zhang, Hongmei Zhang, Biao Qin, Mongur Hossain, Ying Huangfu, Jialing Liu, Kun He, Ping Lü, Wei Li, Feng Ding, Ruixia Wu, Bo Li, Jia Li, Xidong Duan
Abstract
Abstract Highcarrier concentration and low mobility in Bi 2 Se 3 hide thetopological surface states (TSS). In the 2D ternary topological insulator (TI) Bi 2–x Sb x Se 3 ,compensatory Sb doping regulates the carrier concentration and mobility withambipolar performance, together with the ultrathin thickness; these factorsmake the TSS in the 2D ternary TI Bi 2–x Sb x Se 3 more observable. Here, a chemical vapor deposition (CVD) method is provided for synthesizing ultrathin Sb‐doped Bi 2 Se 3 nanoplates with dimensions of 2–126 nm in thickness, 3–100 µm in lateral size, and an average Sb doping ranging from 0.15 ≤ x ≤ 0.75. Bi 2–x Sb x Se 3 field effect transistors and Hall devices are manufactured to determine the carrier concentration and mobility of the obtained Bi 2–x Sb x Se 3 nanoplates. These findings demonstrate that the 2D carrier concentration for Bi 2–x Sb x Se 3 nanoplates can decrease up to 1.6 × 10 12 cm –2 . Furthermore, field‐effect mobility and Hall mobility of up to 3411 cm 2 V –1 s –1 and 6462 cm 2 V –1 s –1 , respectively, are realized. A strong ambipolar field effect is found in low‐carrier‐density Bi 2–x Sb x Se 3 nanoplates, proving that these nanostructures may be freely controlled in terms of carrier type and concentration. The synthesis of high‐quality Bi 2–x Sb x Se 3 nanoplates with low‐carrier concentration and high‐mobility provides a platform for investigating TI characteristics more clearly.