Study On Preparation And Growth Mechanism Of MoS₂/Graphene Heterostructure

With the rapid development of silicon-based microelectronics technology,the integration of electronic chips becomes higher and higher,which requires the size of electronic devices to be smaller.At present,the integration of integrated circuits has increased by 1 million times compared with the 1970s.The number of transistors on each IC has grown from 2000 to more than 2 billion,and the line width has shrunk from 4?m to 22 nm,only 1/200 at the time.However,with the increasing integration of electronic devices,the development of electronic devices is beginning to be interfered by quantum effects.Therefore,researchers are beginning to focus on the ultra-thin heterostructure electronic devices formed by two-dimensional layered materials.MoS₂/graphene is a typical type of two-dimensional layer structure heterostructure.At present,a viable approach for controlled preparation of graphene,MoS₂ and their heterostructure remains to be discovered.This standing obstacle severely hinders its practical application.In order to solve this problem,we tried to prepare graphene,MoS₂ and MoS₂/graphene heterostructure in our home-made CVD growth system.The microstructure of MoS₂/graphene heterostructure was characterized to infer the underlying growth mechanism of MoS₂ on graphene surface and provide a direction for MoS₂/graphene heterostructure controllable synthesis.The main contents and results of this paper are as follows:?1?Graphene was prepared on copper foil by chemical vapor deposition?CVD?method.Later,the graphene grown on copper foil was transferred to SiO₂/Si substrate by wet transfer method and used for the growth substrate of MoS₂ and characterization.The characterization results showed that large area monolayer graphene with high quality was obtained by CVD method.?2?We prepared MoS₂ by CVD method on SiO₂/Si substrate and MoO₃ and MoO₂ were used as molybdenum sources respectively tocompare the growth situation of MoS₂.The domain size of most MoS₂ flakes prepared by MoO₃ precursor can reach several hundred microns,but not single layer.A few MoS₂ flake are monolayer and the size is about 5²0?m.On the other hand,the MoS₂ flakes prepared by MoO₂precursors are mainly single layer with size around 20?m,which larger than the sample obtained by mechanical exfoliation.A series of tests were conducted on MoS₂samples prepared by MoO₂ by means of SEM,Raman and photoluminescence spectrum.The characterization results indicate a high quality of MoS₂ sample.?3?MoS₂ was grown by CVD method on the graphene surfaces and so MoS₂/graphene heterostructure was obtained.The characterization results showed that MoS₂ was successfully grown on graphene.In addition to the regular triangular shape of MoS₂,there are MoS₂ nanoribbons extended out of the edge and corner of MoS₂flake along the armchair direction.The microstructure of MoS₂ samples was characterized by spherical aberration-corrected scanning transmission electron microscopy.The edges of MoS₂ flake was mainly combined with molybdenum terminated zigzag edge;At the edge of MoS₂ nanoribbon,it shows an alternating presence of molybdenum and sulfur zigzag edge terminations;While at the apex of the nanoribbon,sulfur terminated zigzag edges become dominant.Taken these results together,we revealed an underlying growth mechanism of MoS₂ grown graphene surface,which may provide a reference for the controllable preparation of MoS₂/graphene heterostructures.