| ZnO is a wide energy gap semiconductor material with the energy gap of 3.37eV,At room temperature,the exciton binding energy is as high as 60meV,and the exciton emission can be achieved by ZnO,which is an important luminescent material.It shows a great potential for development in the blue and violet light emitting devices and transparent electrode of solar cell and so on,so ZnO is the ideal material for the future preparation of ultraviolet laser and ultraviolet light emitting diode.Graphene is a two-dimensional honeycomb lattice structure composed of carbon six membered rings,it can be seen as having a carbon atom thickness(0.335nm)graphite,and has very flexible connection between the carbon atoms,so its structure is very stable.At the same time,graphene is a zero energy gap semiconductor material,because of its high electrical conductivity and thermal conductivity,mechanical properties and other excellent properties,make it become the most ideal hybrid materials and will play an important role in the field of microelectronics.In this paper,we prepared graphene film by CVD method in the first,and analyzed the three factors:the growth temperature,the cooling rate and the time of carbon source.The optimal process for the preparation of single layer graphene film was selected,which is the growth temperature of 1000 DEG C,the cooling rate is rapid cooling(about 25/s),the carbon source entry time is 5min.The growth mechanism of graphene films is also discussed.The growth mechanism of graphene is not only related to the catalytic mechanism of Cu,and also on the cooling rate,graphene formed by the combined effect of the two mechanisms.Then we adopted single factor optimization method,grew the ZnO films by magnetron sputtering on a graphene layer,the four key factors in the process of working pressure,sputtering power,substrate temperature,oxygen and argon flow ratio were optimized.The results of analysis showed that all of the four factors have important effect on the crystallinity of ZnO thin films,sputtering power,argon oxygen flow rate and substrate temperature on the crystal quality of the films is far greater than the working pressure,substrate temperature and oxygen flow ratio of argon to influence the preferred orientation of ZnO films is more significant.The optimum process parameters for preparing ZnO thin films are as follows:working pressure:0.5 Pa,sputtering power:200 W,substrate temperature:150 degrees C,Ar and O2 flow ratio:35:5.Finally,we analyzed the optical properties of ZnO/graphene composites and ZnO grown directly on Cu films under the optimal process,and investigated the mechanism of the effect of graphene on the optical properties of ZnO.The results show that the presence of graphene can not only improve the crystalline quality of ZnO films,but also enhance the luminescence properties of ZnO.We also studied the optical performance of different thickness ZnO and different layers of graphene composite,the results show that the ZnO film with sputtering time of 10min and graphene layer with 3-5 layers,ZnO films have the best crystallinity and the strongest optical properties. |
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