Direct Growth Of Graphene On Insulating Substrates And Its Applications

As a two-dimensional material with atomic thickness,graphene exhibits unique electronic,thermal,optical and mechanical properties and chemical stability,which is promising for the next generation of electronic and optical devices.In recent years,synthesis of graphene via chemival vapor deposition(CVD)method has been adopted due to its good controllability,as well as high quality of the obtained graphene.Although scalable graphene has been successfully synthesized on metal substrates,the graphene needs to be transferred onto insulating substrates for further applications,which would cause the damages and contaminations of graphene.To avoid these issues,scientists have focused on the direct growth of graphene on insularting substrates.However,there are still two issues for the direct growth and applications of graphene:1)the fast growth of large-area uniform graphene is one of the major challenges of graphene growth on insulating substrates;2)the influence of the interface between graphene and substrate on the final device performance still remains in blank.Accordingly,this paper focused on the controllable growth of large-area graphene on insulating substrates,and the applications of prepared graphene have also been explored.And we also investigated the conformal coating of graphene in any arbitrary shapes,even 3D irregular shapes.Meanwhile,the hexagonal boron nitride(h-BN)single crystals have been synthesized on liquid copper(Cu),where the self-aligned single-crystalline h-BN array has been first demonstrated.The main contents are listed as follows:(1)Direct growth of large-area uniform single-layer graphene on quartz with the assistance of gallium(Ga)vapor and construction of ultra-fast graphene transparent defogger.It has been demonstrated that the Ga vapor could effectively improve the quality of graphene and decrease the growth time.The first practical single-layer graphene defogger has been fabricated.The directly grown graphene exhibited ultra-fast defogging time for relative low input voltage.When applied a safe voltage of 32 V,it can completely remove the fog within 5 s,and the graphene defogger showed good stability.These outstanding performances were atrributed to the strong interaction between the graphene and the substrates.(2)Direct growth of conformal graphene on arbitrary-shape ceramics via rationally designing a compatible strategy with the fabrication of traditional ceramics.These graphene coatings were intimately adhered on the arbitrary-shape,even 3D irregular ceramic products,which could be customized according to the demands of applications.Moreover,the graphene film exhibited uniform distribution and high quality even on the concave and convex surfaces.To confirm the performance of these arbitrary-shaped graphene ceramics,heating devices and electroluminescent devices have been fabricated by utilizing the graphene ceramics as key components.The saturated temperature of the graphene ceramic heater could reach 160 ? when we applied a voltage of 3 V and exhibited a negligible resistance change over 250 h.(3)Direct growth of graphene on nanoscale ceramics.We mixed micro-ceramic with nickel(Ni)powder to obtain nanoscale ceramic powder by ball-milling technique.The graphene has been demonstrated by transmission electron microscopy(TEM)that it was intimately adhered on the ceramic particals.After spark plasma sintering(SPS),the nanophase graphene ceramic bulk has been succesfully obtained.The graphene showed high quality and uniform distribution in the bulk and exhibited good electronic conductivity and mechanical property.(4)Synthesis of hexagonal boron nitride(h-BN)single crystals and self-aligned single-crystalline h-BN array on liquid copper surface.Due to the isotropic homogeneity and smooth surface of liquid surface,circular h-BN domain has been firstly observed.And the h-BN single crystals tended to arrange into uniform array with accordant spatial orientation.The h-BN single-crystalline array aligned orderly and distributed uniformly.Moreover,the domain size of the h-BN single-crystalline array was homogenous.And the h-BN domains also showed an accordant spatial orientation.