) Thin Films

Due to the gapless conductive surface states which are protected against perturbations, topological insulator materials have attracted much attention in this field. Bi₄I₄ is a quasi-one-dimensional van der Waals material, and its beta phase has been revealed by angle-resolved photoemission spectroscopy to be a topological insulator, thus offering a new platform for exploring topological phases. To date, all prior works on Bi₄I₄ are based on the bulk material. Here we report transport measurements of thin Bi₄I₄ films that are mechanically exfoliated Bi₄I₄ from bulk crystals. Devices in both alpha and beta phases are characterized. Their gate-tunable resistance demonstrates surface-dominated transport, which is further supported by the observation of weak antilocalization in magnetic fields. Moreover, the temperature behavior in b-Bi₄I₄ suggests that the inelastic scattering process at low temperature is dominated by the electron-electron interaction.