Comprehensive First-Principles Engineering of TM-Doped InP Nanosheets for Multifunctional Device Platforms: Spintronics and Optoelectronics

Spin-polarized density-functional calculations were carried out to clarify how the incorporation of 3d transition-metal atoms (V, Cr, Mn, Fe, Co, Cu) alters the behavior of two-dimensional indium phosphide nanosheets. The undoped InP monolayer behaves as a non-magnetic indirect semiconductor, and its band gap systematically narrows as the thickness increases due to the weakening of quantum-confinement effects. Substitution with TM elements introduces localized 3d-derived defect states inside the intrinsic band gap and produces strong spin asymmetry. Magnetic moments were calculated, showing Mn-doped InP nanosheets exhibit the highest magnetic moment of approximately 5.63 µB at a concentration of 6.25%. The Cr, Co- and Cudoped nanosheets acquire half-metallic characteristics. Mn-, V-, and Fe-doped systems retain semiconducting features with spin-dependent energy gaps. The computed dielectric response reveals additional low-energy peaks arising from dopant-induced defect and intraband transitions, with Cu-doped systems showing a significant shift in optical absorption towards the infrared region. Overall, the results show that TM substitution provides an effective route for tuning the magnetic behavior and optical absorption of InP nanosheets, opening pathways toward nextgeneration spintronic and visible-to-near-infrared optoelectronic technologies.