Study On The Optical Properties Of PtSe₂ Based On Spectroscopic Ellipsometry

Pt Se₂,an emerging 2D group-10 transition metal dichalcogenide?TMD?,shows high carrier mobility at room temperature and high stability in the air.Besides,the band structure,absorption spectrum and raman spectrum of Pt Se₂ films show strong dependence on the thickness.When it going from bulk to few-layer,Pt Se₂ undergoes a semimetal-to-semiconductor transition.These excellent properties make Pt Se₂show a wide application prospect in the field of photoelectric devices.The design and performance analysis of photoelectric devices based on Pt Se₂ require depth understanding on its linear optical properties and optical constant.The optical constant spectrum can reflect the linear optical properties of Pt Se₂.Spectroscopic ellipsometry is a sensitive??0.1??and nondestructive technique to measure the optical constant and thickness of 2D materials.Benefitting by the properties of high accuracy and nondestructive,spectroscopic ellipsometry is widely used in the measurement of optical thin films.The following works were done to measure the optical properties and optical constant of chemical vapor deposition-grown Pt Se₂with different thickness.Firstly,the flatness of the samples were measured by optical microscope and atomic force microscope.Then,the x-ray photoemission spectroscopy confirmed the composition of the sample,which showed that our samples are composed of only Pt and Se elements.Besides,the Se:Pt stoichiometric ratios indicated the p-type doping in these films.The lattice structure of the samples were characterized by raman spectrum,which evinced the high quality of samples.The measured absorption spectra,Fourier transform infrared spectroscopy and electrical transport characterization reveal the coexistence of both semiconducting and metallic contents in these Pt Se₂ films.Polarized optical microscopy and polarization absorption measurements reveal the isotropic in-plane optical response of these continuous Pt Se₂ films in a scale size of at least as small as 143×108?m².Finally,parametersand?of the samples were obtained by spectroscopic ellipsometry.The optical constant,including refractive index9),extinction coefficient,complex dielectric constant?₁ and₂?as well as thickness of the samples were extracted by data fitting.The values of9)andof Pt Se₂ were found to have a strong dependence on the thickness and they decrease as the reduction of the thickness.The tunable optical constants are conducive to provide vital parameters for precise optical analysis and analog simulation,promoting future developments and applications of Pt Se₂.