Magnetotransport study of (Sb_1-xBi_x)₂Te₃ thin films on mica substrate for ideal topological insulator

In this study, we deposited high quality (Sb_1xBi_x)₂Te₃ on mica substrate by molecular beam epitaxy and investigated their magnetotransport properties. It is found that the average surface roughness of thin films is lower than 2 nm. Moreover, a local maxima on the sheet resistance is obtained with x = 0.043, indicating a minimization of bulk conductivity at this composition. For (Sb_0.957Bi_0.043)₂Te₃, weak antilocalization with coefficient of -0.43 is observed, confirming the existence of 2D surface states. Moreover Shubnikov-de Hass oscillation behavior occurs under high magnetic field. The 2D carrier density is then determined as 0.81 x 10¹⁶ m^-2, which is lower than that of most TIs reported previously, indicating that (Sb_0.957Bi_0.043)₂Te₃ is close to ideal TI composition of which the Dirac point and Fermi surface cross within the bulk bandgap. Our results thus demonstrate the best estimated composition for ideal TI is close to (Sb_0.957Bi_0.043)₂Te₃ and will be helpful for designing TI-based devices