**4. Effect of laser polarization over different thicknesses of PtSe2**

The state of laser polarisation during Raman spectroscopy affects the two prominent modes of vibration i.e., *E*g (in plane) and *A*1g (out of plane) mode. **Figure 11a** and **b** shows the 1 nm (a) and 5 nm CVD grown PtSe2 under vertical (Z(YY)-Z) and horizontal (Z(YX)-Z) polarization [15]. For the 1 nm film, the intensity out of plane (*A*1g) mode significantly varies under vertical and horizontal polarization, whereas the 5 nm film has considerably less variation. When the thickness is increased to 59 nm (flake 2, **Figure 11c**) the intensity is almost similar under both states of polarization. This is because for the thicker film, the contribution from the bottom layers is more prominent and makes the intensities similar. The state of polarization has no effect over the intensity of the in-plane mode for 1 nm and 59 nm, this is because of it's planar nature of vibration.

**Figure 11.**

*Raman spectra of CVD grown (a) 1 nm and (b) 5 nm films of PtSe2 [15] (c) flake 2 of present work under parallel and horizontal polarization.*
