Synthesis of the 2D Ternary Topological Insulator Bi_2-xSb_xSe₃ with a Low Carrier Concentration and Ultrahigh Carrier Mobility

Highcarrier concentration and low mobility in Bi₂Se₃ hide thetopological surface states (TSS). In the 2D ternary topological insulator (TI) Bi_2–xSb_xSe₃,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–xSb_xSe₃ more observable. Here, a chemical vapor deposition (CVD) method is provided for synthesizing ultrathin Sb-doped Bi₂Se₃ 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–xSb_xSe₃ field effect transistors and Hall devices are manufactured to determine the carrier concentration and mobility of the obtained Bi_2–xSb_xSe₃ nanoplates. These findings demonstrate that the 2D carrier concentration for Bi_2–xSb_xSe₃ nanoplates can decrease up to 1.6 × 10¹² cm^–2. Furthermore, field-effect mobility and Hall mobility of up to 3411 cm² V^–1s^–1 and 6462 cm² V^–1 s^–1, respectively, are realized. A strong ambipolar field effect is found in low-carrier-density Bi_2–xSb_xSe₃ nanoplates, proving that these nanostructures may be freely controlled in terms of carrier type and concentration. The synthesis of high-quality Bi_2–xSb_xSe₃ nanoplates with low-carrier concentration and high-mobility provides a platform for investigating TI characteristics more clearly.