Optical properties of chemical vapor deposition-grown PtSe2 characterized by spectroscopic ellipsometry

PtSe2, an emerging 2D group-10 transition metal dichalcogenide (TMD), has aroused significant attention recently due to its intriguing physical properties. Here, the optical properties of chemical vapor deposition-grown PtSe2 films with different thicknesses were characterized with nondestructive spectroscopic ellipsometry and Fourier transform infrared spectroscopy. The polarized optical microscopy reveals the isotropic in-plane optical response of the continuous PtSe2 films in a scale size of at least as small as 143 x 108 mu m(2). The electrical transport characterization and UV-mid infrared absorption spectra reveal the coexistence of both semiconducting and metallic contents in these PtSe2 films, making PtSe2 quite different among the 2D material family. The effective refractive index (n) and the extinction coefficient (k) over a spectra range of 360-1700 nm were obtained. In contrast to other TMDs, the values of n and k of PtSe2 were found to have a strong dependence on the thickness and they decrease as the reduction of thickness. This work is conducive to provide vital parameters for further study on PtSe2 and could facilitate its application in optoelectronic devices.