Investigation On Structure Property Of Si Grown On Ag Films Substrates Using Very-high-frequency Magnetron Sputtering

With the development of graphene,another two-dimensional honeycomb lattice similar to that of graphene has attracted a great deal of attention,that is the silicene.However,the two-dimensional honeycomb lattice of Si can not exist in nature as that of the graphene because the binding between silicon atoms is in the sp~3-bonded state,not in the sp~2-bonded state as that of carbon atoms.Thus,the two-dimensional honeycomb lattice of Si must be grown by epitaxial method on the metal substrate with two-dimension honeycomb structure,such as the(111)surface of bulk crystalline Ag and the ultra-thin Ag(111)films.However,the major technology currently used to grow the silicene is the ultra-high-vacuum evaporation epitaxy,which required a strict control of evaporated Si amount and substrate temperature,making the synthesis of silicene remain a very challenging.Recently,the investigations on the very-high-frequency(VHF)magnetron sputtering discharge showed that the ions produced by the VHF magnetron sputtering had a very low flux density and a higher energy.This feature is fit for the growth of Si two-dimensional nano-structure,because the higher ions energy is help to enhance the surface diffusion of silicon adatoms,making the silicon adatoms reach a position with low surface energy,while the lower ions flux can control the number of silicon onto the substrate,reducing the rapid spatial growth.This stimulates our curiosity about whether the Si two-dimensional honeycomb lattice can be prepared using the VHF magnetron sputtering.Therefore,in this work,the growth and structures of silicon on Ag films by the 40.68 MHz and 60 MHz VHF magnetron sputtering were investigated.This thesis studies the effect of Ag films underlayer on the growth of silicon deposited by the 40.68 MHz VHF magnetron sputtering.It is found that for the Ag films with the(111)preferred orientation,the surface diffusion of Si adatoms and the growth at the position with the lowest surface energy leads to the formation of big particles structure.While for the Ag films with more energetically unstable orientations,the surface diffusion of Si adatom to the position with the lowest surface energy is hindered.The two-dimensional growth of silicon on Ag films dominates the growth behavior,thus forming the oriented hollowed-particles structure.The effect of driving frequency on the structure of silicon grown on Ag(111)films was further investigated in this thesis,which were prepared using the 40.68 MHz and 60 MHz very-high-frequency(VHF)magnetron sputtering.It is found that for the 60 MHz VHF magnetron sputtering,the surfaces of silicon on Ag(111)films exhibit a small cones structure,similar to that of Ag(111)films substrates,indicating a better microstructure continuity.However,for the 40.68 MHz VHF magnetron sputtering,the surfaces of silicon on Ag(111)films show a hybrid structure of hollowed-cones and hollowed-particles,completely different from that of Ag(111)films.The change of silicon structures is closely related to the difference in the ions energy and flux density controlled by the driving frequency of sputtering.Although the silicene can not be obtained currently by the VHF magnetron sputtering,the two-dimensional growth of silicon has been achieved.This encourages us to explore the possible condition to prepare silicene using the VHF magnetron sputtering.