Phonon Structure And Thermal Properties Of Graphene

Graphene (single layer of carbon atoms) has been becoming one of the most hottest system because its special structure and the physical property. Graphene has no internal defects with extremely thin and obvious quantum effects, so that it has different characteristics from other two-dimensional physical systems. Graphene has similar functions to those of carbon nanotubes, with outstanding and unique physical, chemical and mechanical properties, and has extensive applications in the design of devices of micro-nano-electronics, optoelectronics and spintronics.Starting from the sp2 hybrid orbit theory for carbon and lattice dynamics, this thesis studied the formation of crystal graphene (monlayer of carbon atoms) and its phonon structure. Both the in-plane and out-off plane lattice vibrational dispersions have been calculated. Furthermore, the specific heat and Debye temperature have been calculated and discussed by using the dispersion relations.The thesis is divided into five chapters. The first chapter introduces briefly the research history and the present situation in graphene. Basing on the linear combination of orbit wave functions of carbon atoms, chapter two calculates the concrete expressions of sp2 hybridization orbit wave functions of graphene covalent bonds, except for the experimental manufacturing and potential applications of graphene. The third chapter presents the acoustics phonon structure of grapheme basing on the dynamics theorem of crystal lattice. According to the characteristics of graphene crystal structure, we have drawn the lattice structure of graphene primitive cell and investigated the dynamics characteristics of the center of mass vibration, and obtained the in-plane and out-off-plane vibration dispersions but for the velocity of atoms. Chapter four discusses the crystal lattice vibration specific heat in graphene. Finally we calculate the graphene Debye temperature and find that the graphene crystal vibration specific heat is proportional to the absolute temperature T2 in the low temperatures. Chapter three and four are our works.In chapter five, a summary of the work and a outlook of this topic are given.