Weak Antilocalization Effect for Detection of Dirac Fermions in Capped Bi ₂ Te ₃ Epitaxial Film

In this work, the transport properties of a sample grown by molecular beam epitaxy are investigated. The sample is composed of a 15 nm ‐ thick bismuth telluride (Bi 2 Te 3 ) epitaxial film deposited on a barium fluoride (BaF 2 ) (111) substrate and capped with a 75 nm BaF 2 cover layer, which aims to prevent the topological surface states (TSSs) deterioration. Electrical resistance temperature dependence shows a transition from metallic to insulating behavior at ≈20 K as the temperature decreases. A detailed analysis of this behavior indicates a transition of the dominant conduction channel from bulk to TSS. Magnetoresistance (MR) measurements are performed in the temperature range of 1.9–200 K, and for high magnetic fields ( B > 3 T), linear MR is observed at temperatures below 30 K, which also suggests the presence of TSSs. At low fields and low temperatures, MR curves exhibit a weak antilocalization effect. The experimental data are analyzed using the Hikami–Larkin–Nagaoka (HLN) equation. The obtained parameters of the HLN equation indicate the presence of two conduction channels at low temperature, and at least one of them originates from TSSs. The implementation of the cap layer successfully protects the TSSs and keeps the good performance of the electrical signal in the samples.