Fig. 1. Flow chart of the preparation of 2H-MoTe₂ quantum dots

Fig. 2. Size，morphology，structure and composition analysis of MoTe₂ quantum dots：（a）TEM image of 10.5 nm quantum dots；（b）TEM image of 3.0 nm quantum dots；（c）HRTEM images of 10.5 nm and 3.0 nm quantum dots；（d）XRD pattern of 10.5 nm quantum dots；（e）Raman spectrum of 10.5 nm quantum dots；（f）FTIR spectrum of 10.5 nm quantum dots

Fig. 3. SEM and UV-Vis-NIR absorption spectrum of MoTe₂ quantum dot films：the top-view SEM images of the quantum dot films：（a）the particle size is 10.5 nm，（d）the particle size is 3.0 nm；the cross-sectional SEM image of the quantum dot films：（b）the particle size is 10.5 nm，（e）the particle size is 3.0 nm；the UV-Vis-NIR absorption spectrum of quantum dot films：（c）the particle size is 10.5 nm，（f）the particle size is 3.0 nm（insets are the pictures of the films）

Fig. 4. （a）The schematic diagram of the spectroscopic ellipsometry device；（b）the models of 2H-MoTe₂ quantum dot film

Fig. 5. The spectroscopic ellipsometry fitted results using B-spline model of MoTe₂ quantum dot film with the size of 10.5 nm：（a，b）the ellipsometric parameters；（c）the tested and the fitted values of n，k；（d）the tested and the fitted values of the dielectric constants ε₁ and ε₂

Fig. 6. The spectroscopic parameters fitted results using Tauc-Lorentz model of MoTe₂ quantum dot film with the size of 3.0 nm：（a，b）the ellipsometric parameters；（c）the tested and fitted values of n，k；（d）the tested and fitted values of the dielectric constants ε₁ and ε₂