Preparation And Field Emission Properties Of DLC And DLC Composite Films By Liquid Electrochemical Deposition

Diamond-like carbon(DLC)is a metastable form of amorphous carbon mainly containing sp3 and sp2 bondings.Due to their exceptional properties such as high hardness,high electrical resistivity,high transparency to visible light,high chemical inertness and biological compatibility,DLC films have found several applications in the fields of mechanics,electricity,bioengineering and optics,etc.,especially as field emission cathodes in vacuum micro-electronics.The field emission properties and mechanism of DLC films have been paid extensive attention in recent years.The vapor deposition of DLC films has been comparatively developed.However,it is very difficult and costly to accomplish the three-dimensional(3D)deposition and doping,and the applications of the resulting DLC films have been limited due to the complicated equipment and high substrate temperature.Liquid electrochemical deposition showed several advantages over vapor deposition,including simplicity of the experimental setup,low process temperature,and controllability.Furthermore,it is possible to make 3D deposition of DLC films by electrodeposition.The electrochemical deposition of DLC films has made great progress in recent years.The research work is concerned with the preparation and ZnO and metal nanoparticales doping of DLC films by electrochemical deposition.The field electron emission properties of the resulting films were also investigated.The main research contents of this thesis are shown as follows:1.By using simple electrochemical equipment and pure graphite anode,DLC films were electrodeposited on stainless steel substrates varying in size.It was shown that for the substrate larger than the anode,DLC films could be only electrodeposited on the surface across the anode,but for the substrate smller than the anode,DLC films could be simultaneously electrodeposited on both surfaces of the substrates.Raman spectra showed that the microstructures of the DLC films were very similar.The thickness distribution of the film was uniform.According to quasistatic electric field theory,the experimental results were explained,and a theory foundation was put forward for the 3D electrodeposion of DLC films on conductive substrates with complex surfaces.2.At ambient pressure,the ZnO nanoparticles doped DLC films were electrodeposited by the electrolysis of Zn2[C32H42N8O13]Cl4/methanol solution under different voltages.The composition and microstructure were characterized by XPS,Raman,AFM and TEM techniques.The results confirmed that the embedded wurtzite-structured ZnO nanoparticles increased with the increase of the applied voltages,and the ZnO nanoparticles embedding could enhance graphitization of DLC matrix.Also,the field electron emission(FEE)properties of the ZnO-DLC film were improved.3.Nano-scale metallic particles were homogeneously embedded in DLC films by electrochemical deposition technique.The results of XPS,Raman,SEM and TEM tests conformed the content and sizes of the metal nanoparticles increased with the applied voltages increasing.The embedding of Fe nanoparticles aroused the increase of sp3 content of the DLC matrix,while the embedding of Co and Ni nanoparticles enhanced the graphitization of the matrix.The Fe and Co nanoparticles embedding could improve the field emission properties of the composite films while the Ni embedding could depress the properties.The changes in the field emission properties were interpreted in terms of both the morphology and microstructure transformation.