Rapid Preparation Of Large Area Single Crystal Graphene Thin Films By Chemical Vapor Deposition And Performance Of Graphene-based Devices

Graphene has been hailed as a new nanomaterial in the 21st century by the scientific community because of its excellent optical,mechanical,and electrical properties.The chemical vapor deposition(CVD)method has become the mainstream preparation technology in the laboratory since it successfully prepared high-quality graphene films.However,commercial production is not possible because preparing large-area single crystal graphene needs long time,so there is a huge gap between the laboratory preparation of large-sized single crystal graphene and its practical application.By adjusting the pretreatment of copper foil,annealing of copper foil and pressure of CVD,continuous and single crystal graphene films on copper(Cu)are synthesized by low pressure chemical vapor deposition(LPCVD)in the growth time of 40 minutes with the meticulously modulation of the oxygen and carbon supply in multistages synthesis processing and graphene properties dependence on the oxygen and carbon supply has been investigated.Oxygen is introduced twice before the nucleation and growth stages.The time and flow are 10min/1min and 1.5sccm/lsccm,and the growth pressure is controlled at 150 pa.By using scanning electron microscopy,the size of the graphene film can be clearly observed to be about 300um,and it can be seen as a uniform two-layer graphene by Raman characterization.In this paper,conventional photolithography and evaporation methods are used to prepare graphene-based field effect transistors(FET)and test their carrier mobility.It reveals the superior hole mobility of4347 cm2V-1s-1.A graphene-based gas sensor was prepared by using the grown double-layer graphene,and the effect of ultraviolet ozone treatment on the performance of the graphene gas sensor was explored.It's found that the surface properties of graphene films can be changed by ultraviolet ozone treatment.The Raman test spectrum showed that the peak of the defect peak D of the graphene film became larger with the increase of UV-ozone treatment time,however,with the increase of processing time,the result of the sensitivity to NO2 increased first then decreased.The experiments show that when the UV-ozone irradiation time is 75s,the response sensitivity of the device to a concentration of 0.15ppm NO2 gas reaches 33%,and its restore performance is stably maintained at 80%.The research of this device has laid a certain foundation for the practical application of gas sensors.