Optical identification of MoS2/graphene heterostructure on SiO2/Si substrate.

Chemical vapor deposition (CVD) method is considered to be an efficient way to prepare Van der Waals heterostructure. However, accurately and hurtlessly identifying the layers number of MoS(2) in the heterostructure is still a challenge. Here, we calculated the expected contrast between MoS(2)/graphene heterostructure and underlying SiO(2)/Si substrate by using a Fresnel law based model. And we indicated that contrast at blue and green incident light is ideal for visibility and layer number detecting. Our measured value showed good agreement with calculated ones. And Raman spectrum helped to confirm our speculation.