Ultrafast and Steady-State Optical Characterization of Multilayer PdS2

Abstract

Palladium disulfide (PdS₂), a noble-metal transition metal dichalcogenide with an unusual puckered orthorhombic structure, is of interest for fundamental research and optoelectronic applications due to its distinctive optical properties. Despite this potential, PdS₂ itself remains relatively underexplored. Here, we characterize the steady-state and ultrafast optical properties of multilayer PdS₂ film using polarization-dependent Raman and second-harmonic generation microscopy, ellipsometry, and ultrafast differential reflectance. We extract the dielectric function, an indirect bandgap of 1.25 eV and confirm the 2O phase. Ultrafast measurements reveal multi-timescale dynamics, including a two-step decay (370 fs and 1.1 ps) and blueshift during photoinduced carrier relaxation, as well as coherent phonon oscillations of the A_g¹ optical mode. Long-lived carrier recombination is described by a biexponential decay with time constants of 240 ps and 2 ns. These results provide insight into the ultrafast dynamics and optoelectronic properties of PdS₂, and may open new possibilities for its use in photonic and optoelectronic devices.