Topological Insulator Thin Film Fabrication and Electronic Property Investigation for Novel Spintronic Device Applications

Background: Topological insulators exhibit protected surface states with spin-momentum locking that enable dissipationless spin transport, with transformative potential for spintronic devices. Fabrication and characterisation of topological insulator thin films under accessible laboratory conditions, and development of a theoretical framework for their Nigerian application contexts, represents a frontier research opportunity. Aim: This study fabricated topological insulator Bi2Se3 and Bi2Te3 thin films by thermal evaporation and investigated their electronic properties for spintronic device applications. Methods: Thin films of varying thickness from 3 to 100 nm were deposited by co-evaporation on mica and SiO2 substrates. Structural characterisation used RHEED, XRD, and Raman spectroscopy. Magneto-transport measurements from 2 to 300 K in magnetic fields up to 9 T characterised topological surface state signatures including weak anti-localisation and quantum oscillations. Spin Hall angle and spin diffusion length were measured by second harmonic Hall measurement. Results: Weak anti-localisation signatures confirming topological surface state transport were resolved in films above 10 nm thickness. Spin Hall angle of 0.24 and spin diffusion length of 38 nm were measured at 300 K, competitive with conventional heavy metal spintronic materials. Quantum oscillation analysis confirmed Dirac surface state carriers. Conclusion: Thermal evaporation-grown Bi2Se3 films exhibit topological insulator electronic properties suitable for spintronic applications. A roadmap for topological spintronics research at Nigerian universities is proposed. Keywords: topological insulator, thin film, spintronics, Bi2Se3, spin Hall effect.