Fig. 1. Schematic of three-zone CVD method

Fig. 2. Surface morphology analysis of PtSe₂. (a) Optical photographs of the substrate and 2, 4, and 6 layers of PtSe₂; (b) micrograph of 4L PtSe₂ with a magnification of 100×; (c) AFM image of 4L PtSe₂ with the scratch method showing the sample thickness of 2.2nm

Fig. 3. Raman spectral analysis of PtSe₂. (a) Raman spectra of 2, 4, and 6 layers of PtSe₂; (b) variation of the peak positions of E_g and A_1g peaks with the number of layers

Fig. 4. Analysis of the transmission spectra of PtSe₂. (a) Transmission spectra; (b) Tauc plots, the lines are the optical bandgaps estimated by the intercept method

Fig. 5. Test and fitting results of ellipsometric parameters for PtSe₂ films with different layers. (a) Test and fitting results of ψ; (b) test and fitting results of Δ

Fig. 6. Optical constants of PtSe₂ films with different layers. (a) Refractive index; (b) extinction coefficient; (c) real part of the dielectric function; (d) imaginary part of the dielectric function

Fig. 7. Temperature-dependent optical constants of PtSe₂ films. (a) (c) Refractive index and extinction coefficient of 4L PtSe₂; (b) (d) refractive index and extinction coefficient of 6L PtSe₂

Fig. 8. The thermo-optical coefficient of PtSe₂ films as a function of wavelength