Electronic Structure Reorganization in MPS₃ via d-Shell-Selective Alkali Metal Doping

Semiconducting two-dimensional (2D) antiferromagnetic (AFM) transition-metal thiophosphates (MPS₃) offer promising opportunities for spintronic applications due to their highly tunable electronic properties. While alloying and intercalation have been shown to modulate ground states, the role of d-shell filling in governing these transitions remains insufficiently understood. Here, we investigate electron doping effects in MPS₃ using angle-resolved photoemission spectroscopy (ARPES), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT+U). Lithium and cesium deposition are employed to induce doping across different MPS₃ compounds. We identify two distinct doping mechanisms: in MnPS₃, electrons are primarily donated to the P₂S₆ ligand clusters, with negligible Mn 2p core-level shifts and no major changes in the valence band. In contrast, FePS₃, CoPS₃, and NiPS₃ exhibit clear reductions in transition-metal oxidation states, with a ∼1.0 eV reduction in spin-orbit splitting for Co upon doping. ARPES on CoPS₃ reveals a ∼400 meV shift of Co-derived bands toward higher binding energies and new dispersive states up to 1 eV above the valence band maximum, indicating metallic behavior. These results establish a direct correlation between d-shell filling and doping response, highlighting alkali metal doping as a tunable route to tailor the electronic and magnetic properties of 2D AFM semiconductors for spintronic applications.