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 fornext-generationtwo-dimensional electronic and optoelectronic devices. The performanceof such devices is completely determined by the properties of theinterface. However, due to a lack of contamination-free fabricationtechniques, obtaining an ideal interface is still a challenge. Meanwhile,the efficiency of photodetectors and solar cells is highly dependenton the charge separation on the interface. Thus, the questions onthe effect of interfacial conditions on a contact type, charge redistribution,and photoluminescence still exist. In this work, the effect of interfacialconditions on the optical and electronic properties of MoSe2/Au heterostructure is studied. The tip of an atomic force microscopeis used to clean the interface and change interfacial conditions.Kelvin probe microscopy revealed that the work function of the MoSe2 monolayer increases by 40 meV, the bilayer by 28 meV, andthe trilayer by 12 meV due to charge redistribution after the cleaning.Micro-photoluminescence (& mu;-PL) investigation shows that thecleaning leads to the fall of photoluminescence intensity of about75% for a monolayer and 60% for a bilayer. Raman spectroscopy indicatesthat the cleaning procedure did not damage the MoSe2 flake.It is shown that the presence of interfacial contamination in vdWheterostructures severely affects its electronic and optical properties.The results of the work are of great importance to vdW device fabrication.