Layer-dependent optical and dielectric properties of centimeter-scale PdSe2 films grown by chemical vapor deposition

Palladium diselenide (PdSe 2 ), a new type of two-dimensional noble metal dihalides (NMDCs), has received widespread attention for its excellent electrical and optoelectronic properties. Herein, high-quality continuous centimeter-scale PdSe 2 films with layers in the range of 3L–15L were grown using Chemical Vapor Deposition (CVD) method. The absorption spectra and DFT calculations revealed that the bandgap of the PdSe 2 films decreased with the increasing number of layers, which is due to the enhancement of orbital hybridization. Spectroscopic ellipsometry (SE) analysis shows that PdSe 2 has significant layer-dependent optical and dielectric properties. This is mainly due to the unique strong exciton effect of the thin PdSe 2 film in the UV band. In particular, the effect of temperature on the optical properties of PdSe 2 films was also observed, and the thermo-optical coefficients of PdSe 2 films with the different number of layers were calculated. This study provides fundamental guidance for the fabrication and optimization of PdSe 2 -based optoelectronic devices.