Controllable Preparation And Physical Propertiesof Three Dimensional Structure Graphene

Graphene,a novel two-dimensional material,possessing excellent physical property on optics,electrics,mechanics and thermotics,has become a research hot spot in recent years.In general,CVD method is usually used for preparing planar graphene films with large scale on metal catalyst.The planar CVD graphene needs inevitable transfer processes for applications.However,a transfer process does not only induces contamination,defects,wrinkles,or even breakage of the graphene samples and thus lowers the quality of graphene,but was also difficult to conform the 2D graphene film to the surface of 3D structure device.Only a direct growth technique of graphene on the noncatalytic substrates,and combining with the three-dimensional structure of graphene might provides one of the optional ways to solve the above-mentioned problems.But,until now,the shape of 3D structural graphene is nearly confined to vertical graphene;the reports about direct growth of graphene films on 3D dielectric substrate is very few and the analysis about the physical properties of 3d graphene is also not much.Hence,our works are focused on the preparation and physical properties of 3D structural graphene.Preparing conformal graphene on non-catalytic 3D structural substrates and flexible PDMS for the study of optical,electrical,and mechanical etc.physical performances.Meanwhile,we directly produced high-quality graphene walls（GNWs）on multiple substrates by a universal method,and used a simple and effective air-annealing technique to stably improve the physical properties of defective GNWs.Compositing the CdS NPs on the defective GNWs and researching the photoelectrochemical response performance of composite CdS-GNWs.The surface morphology and structure of 3D micro-strcutural graphene was directly characterized by SEM,Raman spectra,TEM and AFM.An UV–visble–NIR spectrophotometer was used to measure the optical properties of the 3D micro-strcutural graphene.And,the electrical and mechanical of 3D micro-strcutural graphene were cooperatively tested by electrochemical workstation system and four point probe system.The main results of present thesis are as follows,（1）Successfully preparing of continuous conformal graphene films（CGrs）on the surface of grating micro-structured quartz substrates.This CGr possess excellent electrical and optical properties with the sheet resistance of < 2000W˙sq^-1 and the transmittance of > 80%（at 550nm）.And,CGr with more contact spots can be directly used as an electrode in pressure-sensitive sensors,which provide higher sensitivity and repeatability,and faster response time.（2）A continuousand flexible CGrs was successfully prepared on elastomer PDMS.3D structural CGrs possesses excellent optical and electrical properties and supernormalflexibility,especially,monolayer and few-layer CGrs with tensile strain of ²8% and ⁷7.8%,respectively.（3）It is proved that the deposition of GNWs was almost independent on the materials of substrates and it was first proposed that RF-PECVD technique was a versatile approach to grow GNWs.It requires different growth substrates of different plasma source on the preparation of GNWs,and the plasma source would affect the morphology features of GNWs.The growth conditions not only can effectively the morphology characteristics of GNWs,but also can controlthe electricity and physical properties of GNWs.A simple and effective air-annealing technique was developed to stably improve the physical properities of defective GNWs on both the electrical conductivity and light transmission.（4）A mass of CdS nanoparticles（NPs）were inlaied into the 3D network GNWs.The CdS-GNWs nanocomposites with enhanced photoelectronic properties displayed an excellent photocurrent density of 470 mA/cm2.The effective area between CdS nanoparticles（NPs）and GNWs is a crucial factor for the photocurrent density.The photo-current density of CdS-GNWs photo-anode owns wonderful stability as long as dozens of days on laboratory.Research on the electrical,optical and mechanical properties of conformal graphene wouldlay a foundation of 3D graphene,especially would open a new path for the applications on mechanical sensing devices,such as graphene based sensers and graphene based flexible sensers.