Twisting the stacking of layered materials leads to rich new physics. A three-dimensional topological insulator film hosts two-dimensional gapless Dirac electrons on top and bottom surfaces, which, when the film is below some critical thickness, will hybridize and open a gap in the surface state structure. The hybridization gap can be tuned by various parameters such as film thickness and inversion symmetry, according to the literature. The three-dimensional strong topological insulator Bi(Sb)Se(Te) family has layered structures composed of quintuple layers (QLs) stacked together by van der Waals interaction. Here we successfully grow twistedly stacked Sb2Te3 QLs and investigate the effect of twist angels on the hybridization gaps below the thickness limit. It is found that the hybridization gap can be tuned for films of three QLs, which may lead to quantum spin Hall states. Signatures of gap-closing are found in 3-QL films. The successful in situ application of this approach opens a new route to search for exotic physics in topological insulators.
O 12 (BSTO) (x = 0, 0.03, 0.04, 0.05, 0.06 and 0.07) thin films have been fabricated on Pt/Ti/SiO 2 /Si substrates by sol-gel method. The effects of various Sb 3+ content on microstructure and ferroelectric properties of systems are investigated. XRD show that Bi 4-x Sb x Ti 3 O 12 (xࣔ0) thin films prefer (117) orientation. The substitution Sb 3+ for Bi 3+ reduces the grain size of the film surface. Compared to the BTO (x = 0) film, Bi 4-x Sb x Ti 3 O 12 films display exciting electric properties. Especially when x = 0.04, the film Bi 3.96 Sb 0.04 Ti 3 O 12 has achieved the max 2Pr value of 87μC/cm 2 . This film also has a better anti-fatigue characteristic, which can be up to 10 10 switching cycles without fatigue. The leakage current density improved with J = 8×10 −8 A/cm 2 .
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