Intrinsic Traps In The Substrate Regulate CVD Growth Of Graphene

In recent years,many advances have been made in the growth of graphene by chemical vapor deposition（CVD）.However,the process of growing graphene by CVD needs to be carried out at high temperatures.When the graphene is cooled,its surface will form a specific wrinkle structure;In addition,most substrates also have disadvantages such as weak catalytic activity,poor thermal stability,and difficulty in controlling carbon precipitation,resulting in poor continuity,uneven number of layers,and more amorphous carbon in the grown graphene.Therefore,this paper had grown clean and high-quality graphene through a new type of high-entropy alloys substrate.The specific content is as follows:First,the high-quality high-entropy alloys sheet substrates were designed and prepared.The quaternary Fe Co Ni Cu_0.25high-entropy alloys ingots were prepared by arc melting,and the alloy substrates were obtained by plastic deformation,cutting,pretreatment and annealing.By observing and characterizing the microscopic morphology,crystal structure and thermal stability of the thin films,the applicability of the high-entropy alloys substrate were analyzed.Through experiments and characterization,it was found that（1）Granular raw materials were more suitable for the preparation of Fe Co Ni Cu series high-entropy alloys;（2）Pretreatment can reduce the surface roughness and impurity density of high-entropy alloys substrates,and improve the surface finish and uniformity;（3）The surface of the high-entropy alloys substrates had the advantages of uniform element and structure distribution,regular grain size,and no obvious dendrite segregation.The high-entropy alloys substrates before and after annealing were all single solid solution structures,and the annealed alloy substrates were more conducive to graphene growth,and the best annealing time was 30 min;（4）The thermal stability of the high-entropy alloys substrates were good.Under the growth temperature of graphene,the substrate will not undergo desolubilization,over-burning and melting.Secondly,the growth parameters,structure and performance of graphene were explored,including（1）The unpretreated Fe Co Ni Cu_0.25high-entropy alloys sheets were not suitable for growing graphene;（2）Compared with solid carbon source,gaseous carbon source was more suitable for graphene growth,the optimal flow rate of gaseous carbon source（CH₄）was 4 sccm,and the optimal flow rate of H₂was 20 sccm;（3）The optimal growth temperature of graphene was 1040℃,and the optimal growth time was 30 min.Graphene can span growth at the grain boundary of the substrate;（4）APCVD was more suitable for this experiment,no graphene growth under LPCVD;（5）The rapid heating and cooling method was conducive to the growth of graphene with less wrinkles and impurities.Appropriately increasing the heating rate can improve the cleanliness of graphene.Characterization found that the prepared high-quality graphene had the characteristics of large crystal domain size,high integrity,uniform layer number distribution,high degree of crystallization,good continuity,amorphous carbon and few wrinkles.Through performance testing,it was found that graphene had excellent electrical conductivity,corrosion resistance and reusability.Finally,the growth mechanism of high-quality graphene on the surface of the high-entropy alloys was analyzed.High-entropy alloys grow high-quality graphene through the intrinsic trap regulation mechanism with the help of the unique characteristics of delayed diffusion effect,good thermal stability,and low thermal expansion coefficient.The quality of graphene grown on the surface of one-element,two-element,ternary,and five-element substrates was not as high as that of Fe Co Ni Cu_0.25substrate.The growth mechanism of graphene was verified from the perspective of atomic interaction.