Spin Hall effect in platinum deposited by atomic layer deposition

We investigated the spin Hall effect of Pt thin films deposited by atomic layer deposition (ALD) using the MeCpPtMe3 precursor on c-plane sapphire substrates. We show that while the spin Hall conductivity of ALD-grown Pt is relatively low (0.2–0.6 × 105ℏ2eΩ−1 m−1) for Pt film thicknesses less than 7 nm, it suddenly increases for thicker films, reaching 2.5–3.0 × 105ℏ2eΩ−1 m−1. This behavior is attributed to the intrinsic morphology of Pt thin films grown by ALD on sapphire, where ultrathin films (<7 nm) contain small islands, while thicker films are smoother due to the coalescence of islands. Our findings underscore the necessity of growing continuous films when applying ALD-grown spin Hall materials in three-dimensional (3D) spin–orbit torque (SOT) devices. These results confirm the potential of ALD in advancing SOT applications and pave the way for the development of next-generation three-dimensional SOT spintronic devices.