Morphology and magnetism of CoPd coverage on MoS₂ flakes/SiO₂

CoPd alloy nanostructures and thin films were deposited on MoS₂ flakes through e-beam evaporation at a high temperature (HT) (500 K) and at room temperature (RT) (300 K). In HT growth, CoPd nanoparticles assembled at the edge of the MoS₂ flake. The nanoparticles formed parallel chains at the edge of each layer in multilayered MoS₂. As indicated by the quenched photoluminescence, HT deposition resulted in a flat CoPd coverage with a roughness of ≤±0.5 nm on a MoS₂ terrace. By contrast, RT growth led to a relatively rough CoPd thin film on MoS₂ (roughness ≤±2 nm). The film comprised a merged nanoparticle assembly. The MoS₂/SiO₂ step edge played a crucial role in magnetic domain pinning such that the magnetic coercivity (H_c) of Pd/Co/MoS₂ was smaller than that of Pd/Co/SiO₂. Similarly, RT CoPd (8 nm)/MoS₂ exhibited a parallelogram-shaped hysteresis loop with a relatively small H_c value compared with that of the square hysteresis loops of RT CoPd (8 nm)/SiO₂. The hydrogenation of RT CoPd (8 nm)/MoS₂ resulted in reversible H_c enhancement.