Harnessing Chalcogen Chemistry for High-Efficiency Charge-to-Spin Conversion in PtX2 (X = Te, Se) Thin Films.

Efficient charge-to-spin conversion requires strong spin-orbit coupling and tunable electronic transport. Here we use chalcogen chemistry to regulate spin-orbit-torque generation in c-axis-oriented PtX2 (X = Te, Se) thin films. PtTe2/Py and PtSe2/Py heterostructures were fabricated using the same sputtering-chemical vapor deposition and lithographic framework for direct spin-transport comparison. Harmonic Hall measurements, current-partition correction, and thickness-dependent drift-diffusion analysis yield an effective spin Hall angle of θSH ≈ 0.23 for PtSe2/Py, more than twice that of PtTe2/Py (θSH ≈ 0.10). X-ray photoelectron spectroscopy, transport measurements, and bulk electronic-structure calculations link Te-to-Se substitution to changes in Pt-X bonding, near-Fermi-level states, and metallicity. Over the investigated thickness range, PtTe2/Py shows a predominantly bulk-SHE-like response, whereas the larger damping-like torque in PtSe2/Py is consistent with a proximity-modified interfacial contribution. Chalcogen chemistry controls the balance between bulk and interfacial charge-to-spin conversion in Pt-based dichalcogenide heterostructures.