Synthesis of the 2D Ternary Topological Insulator Bi2‐xSbxSe₃ with a Low Carrier Concentration and Ultrahigh Carrier Mobility

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.