the Study on New Approach for Growing Wafer-size Graphene on SiC Substrate and Its Related Properties

Author:Hu Yan Fei

Supervisor:zhang yu ming


Degree Year:2017





As one of principal 2D materials,graphene has a wide application in national defense and economy due to its outstanding physical and electronical properties.However,it is difficult to fully use those advantages of graphene in practical applications,until it is could answer the question how to fabricate high quality graphene.Although many approach have been developed to fabricate graphene,there are mainly four method who could produce graphene for micro-electronics applications,such as: Micro-mechanical exfoliation,CVD on Metal Substrates,Oxidation-reduction graphite,and Epitaxial Growth on Si C.Among the preparation methods,epitaxial growth on Si C is of greatest potentials and breakthrough progress has been made in graphene device by the development of epitaxial graphene on Si C,as a result of its compatibility with existing technology and ready for graphene application.The essentials of epitaxial growth on Si C is Si sublimation from Si C substrate and left C atoms reconstruction into graphene at high temperature and ultra-high vacuum as the fact that Si atoms has higher saturated vapour pressure than C atoms in Si C crystal.Traditional eptaxial growth needs high process temperature and long graphitization time and it requires precise control of gas compositions and vaccum condition,which restrict the synthesis efficiency and quality of epitaxial graphene.Moreover,commo n epitaxial graphene is of lower quality and it is hard to abtain a sizable band gap on epitaxial graphene,which means that the epitaxial graphene cannot be directly used in fabrication of mactro/nano device and related circuit.In this study,epitaxial growth of wafer level graphene on high-pure Si C is investigated experimentally and theoretically centreing on the new process method and related characterization technology.It is hoped to fabricate graphene materials in good quality for special purpose via improving technique and selecting appropriate Si C substrates with the consideration of cast and efficiency.The primary contribution are as follows:1.High quality epitaxial graphene samples has formed on 4H-Si C substrate by face-to-face approach.It requires nucleus equally distributed with moderate density to produce high quality graphene on Si C substrate.Inorder to obtain suitable C atoms nucleation distribution,substrates pretreatment via hydrogen-etching is necessary.Inorder to abtain homegnous nucleation distribution,the effect of hydrogen-etching on the quality of epitaxial graphene is studied in detial.Inorder to abtain conformably Si sublimation,basing on experimental and theoretical study of epitaxial graphene,epitaxial graphene in high quality on Si C forms efficiently by technics renovation and new epitaxial growth method.2.The growth approach of epitaxial graphene on high-purity Si C is further studied.During the investigation of the effect of substrate on epitaxial graphene,it is found that not only the substrate morphology have an impact on the quality of epitaxial graphene,but also the substrate doping make a difference to the quality of epitaxial graphene.Hence,in this part,high purity Si C substrate are used to fabricate graphene and the existing technics are slightly adjusted to produce large area and high mobility epitaxial graphene.It is found that more growth factors are needed to produce high quality epitaxial graphene in highpurity Si C and epitaxial graphen on high-purity Si C has higher quality compared with that on doped Si C.3.The influence of C doping on the epitaxial graphene is studied.Substrate doping not only has an effect on the quality of epitaxial graphene but also on the electronic properties of epitaxial graphene due to the doping change of interface between graphen and Si C.It is found that,on one hand,C doping in Si C lower the growth temperature,and on the other hand,C doping in Si C enhance the transform of electrons into epitaxial graphene from Si C substrates,via the investigation of epitaxal growth on C doped Si C.4.The electronic properties of graphene epitaxal growth on Ⅲ,Ⅴ,Ⅱ,Ⅵ group elements doped Si C substrate was also studied.It is found that those atoms doping Si C could enlarge the band gap of epitaxial graphene,and distinguishing to C doped Si C,those atoms doping in Si C restrain the electrons transform from Si C to epitaxial graphene.5.Based on the abtained research achievements on the new CCS growth approach,fabrication of large area graphene on high-priuty Si C was investageted.Large area epitaxial graphene has been fabricated on Si-face and C-face of high-priuty 4H-Si C.