Preparation Of Stannous Sulfide Nanosheets By Salt Assisted Chemical Vapor Deposition And Its Application In Memristors

In recent years,with the development of traditional silicon-based semiconductor materials bottlenecked,there is an urgent need for a new material that can replace traditional silicon-based semiconductors.Two-dimensional semiconductor materials have excellent mechanical ductility,adjustable band structure,excellent photoelectric effect and extremely small size due to their special structure,and are therefore highly sought after in the fields of flexible devices,photoelectric conversion,catalytic energy storage and microelectronic devices,etc.They are likely to become one of the materials that can replace traditional semiconductors.As a type of 2D semiconductor material,SnS is non-toxic,non-polluting and chemically stable.The constituent elements Sn and S are abundant in nature and are more economical than common metallic 2D materials such as Mo S2,WS,Cd S,etc.Therefore,2D SnS materials have gradually attracted attention in recent years and have been widely used in various fields such as photovoltaic cells and solar cells.In this thesis,SnS nanosheets were grown by chemical vapor deposition(CVD)and salt-assisted chemical vapor deposition(SA-CVD),and the optimal parameters for preparing SnS nanosheets were investigated by orthogonal and comparative experiments.The optimal parameters for the preparation of SnS nanosheets were investigated by orthogonal and comparative experiments,and the Ag/SnS/Au vertical memristorswere prepared by transferring two-dimensional materials and electrodes,and Its electrical performance was tested.The main studies are as follows:(1)The effects of experimental parameters: heating temperature,holding time,gas flow rate and substrate-to-precursor distance on the growth of SnS nanosheets were investigated by designing an orthogonal experimental method.The morphology of the products was characterized by optical microscopy,scanning electron microscopy and atomic force microscopy,the composition of the material specimens was analyzed by energy spectroscopy,and the structure of the specimens was studied by XRD.The growth of SnS nanosheets under different parameters was analyzed.The optimal parameters for the preparation of SnS nanosheets by CVD process were derived.(2)Further optimization of CVD process by adding KCl.Experiments were conducted to compare various methods of adding the auxiliary agent.The results show that the KCl can be stably,cleanly and uniformly adhered to the substrate by physical vapor deposition.The effect of the amount of KCl on the morphology and properties of SnS nanosheets was analyzed by a comparative method using OM and SEM.Based on this,the CVD process was further optimized,and the following conclusions were made:the heating temperature was 650 ℃,the holding time was 1 min,the SnS2 addition was0.02 g,the carrier gas flow rate was 80 sccm,the distance between substrate and precursor was 5 mm.The as-prepared SnS nanosheets with largest area,high frontal occupancy,were uniformly distributed on the substrate,which were well suited for preparing memristors.(3)The approach of using polyvinyl alcohol(PVA)to transfer two-dimensional materials wasinvestigated,and Ag/SnS/Au vertical memristors were prepared by dry transfer.The memristor performance was tested,and it was found that the VSET voltage was located at 2 V,the VRESET voltage was located at-4 V ~-1 V.The LRS and HRS were located at 104 Ω ~105 Ω,respectively,and had good resistance retention characteristics.