Thin Films and FIB-Patterned Single Crystals

Topological Insulators (TIs) have emerged as a novel class of quantum materials predicted to possess an insulating bulk and spin-momentum locked metallic states at the surface produced by a non-trivial topology of the band structure. Bi₂Se₃ is one of the most studied materials in the field, due to its relatively large band gap of 0.3 eV and its simple surface band structure consisting of a single and well-defined Dirac cone.
In the current work, we study the magnetotransport phenomena in Bi₂Se₃ devices patterned following two approaches, starting either from epitaxial thin films grown by pulsed laser deposition or from single crystals. For the fabrication of the devices, we use patterning techniques such as optical lithography and focused ion beam (FIB), including cryogenic milling, and the magnetotransport properties are investigated using fields up to 14 T and temperatures down to 2 K. The main findings to be reported in this contribution refer to a robust weak antilocalization effect in the thin films and to the minimization of ion-induced damage using cryogenic milling. Moreover, strategies to induce superconductivity in Bi₂Se₃ single crystals will also be discussed.