The Study On Photoelectrical Properties Of WSe₂/graphene Heterostructures

Since the concept of van der Waals?vdW?heterostructures based on two-dimensional?2D?materials was put forward,it has attracted a wide range of scientific research as a result of excellent photoelectrical properties the heterostructures performed.In this paper,we introduced the experimental methods and techniques at first,and then studied the basic transport properties of WSe₂ and graphene.Finally,back-gated field-effect transistors based on WSe₂/graphene heterostructures were fabricated,and the photoelectrical properties were systematically discussed and investigated.The main work and conclusions of this paper are as follows:?1?WSe₂/graphene heterostructures were successfully prepared by mechanical exfoliation and deterministic transfer method.Next,the devices were fabricated by standard micro-nano technology.The materials were comprehensively characterized by Atomic Force Measurement,Raman spectrum and so on.?2?The basic transport properties of graphene and WSe₂ were studied.The results indicate that graphene owns high carrier mobility and conductivity,but the on/off ratio and the photo responsivity is extremely low.In contrast,the carrier mobility of WSe₂ is relatively low,but WSe₂ has good photoelectric response and on/off ratio.?3?The device based on WSe₂/graphene heterostructures was successfully fabricated.Its fundamental field-effect characteristic and photo-response performance were systematically studied.In the test,WSe₂/graphene heterostructures exhibited an abnormal transfer characteristic under illumination.Therefore,we propose a mechanism named electro-photo modulation of the band offset in WSe₂/graphene van der Waals heterostructures to explain this novel phenomenon.?4?We put forward a rapid and effective way named ultraviolet-ozone treatment to reduce the negative effect of adhesive residue existing in deterministic transfer method.The results indicate that this adhesive residue may cause poor contact between metal and graphene,thus greatly degenerating the performance of the device.However,this unpleasant influence could be reduced effectively by adopting ultraviolet-ozone treatment.