Effect of Interfacial Contamination on the Charge Redistribution and Photoluminescence of the MoSe₂/Au Heterostructure: Implications for Photodevices

Van der Waals (vdW) heterostructures are promising for next-generation two-dimensional electronic and optoelectronic devices. The performance of such devices is completely determined by the properties of the interface. However, due to a lack of contamination-free fabrication techniques, obtaining an ideal interface is still a challenge. Meanwhile, the efficiency of photodetectors and solar cells is highly dependent on the charge separation on the interface. Thus, the questions on the effect of interfacial conditions on a contact type, charge redistribution, and photoluminescence still exist. In this work, the effect of interfacial conditions on the optical and electronic properties of MoSe 2 /Au heterostructure is studied. The tip of an atomic force microscope is used to clean the interface and change interfacial conditions. Kelvin probe microscopy revealed that the work function of the MoSe 2 monolayer increases by 40 meV, the bilayer by 28 meV, and the trilayer by 12 meV due to charge redistribution after the cleaning. Micro-photoluminescence (μ-PL) investigation shows that the cleaning leads to the fall of photoluminescence intensity of about 75% for a monolayer and 60% for a bilayer. Raman spectroscopy indicates that the cleaning procedure did not damage the MoSe 2 flake. It is shown that the presence of interfacial contamination in vdW heterostructures severely affects its electronic and optical properties. The results of the work are of great importance to vdW device fabrication.