Study On The Preparation And Properties Of Nitride Films Deposited By Physical Vapor Deposition

Transition metal nitrides?TMNs?are currently a hot topic for the application of supercapacitor materials,due to their good electrical conductivity,excellent chemical stability and high cycle stability.Moreover,physical vapor deposition?PVD?is a classical method for preparing nitride films,with the characteristics of easily controlled composition and structure,environmental friendly,good adhesion strenth,and density.However,the electrode materials require high ion contacted surface area.Therefore,this thesis studies preparation of TMNs with specific surface area and porosity by PVD,which can improve the application of nitride films in the field of supercapacitors.The influence of preparation process on the microstructure,electrochemical performance,charge and discharge behavior and cycle stability of the supercapacitor coatings based on TMNs were studied.The storage mechanism was explored,and the supercapacitors films with high capacity and strong cycle stability were obtained By new process methods.In addition,the strategy in this study can provide a good reference for improving the surface morphology and energy storage performance of other transition metal nitrides,oxides and carbides with higher conductivity or theoretical capacitance.The main research results obtained in this work are as follows:1)Films with customized porosity can be prepared by regulating deposition parameters,such as the deposition pressure,Ar/N₂,sputtering angle,deposition time,etc.Suitable deposition pressure can improve deposition rate and crystallinity.The lower Ar/N₂ decreases the deposition efficiency and increases the N content and charge transfer resistance of the film.The film with good crystallinity has lower charge transfer resistance.Gancing sputtering deposition can effectively improve the porosity of thin films,especially the growth of"Z"shape.As for the columnar crystal films,increasing the deposition time makes the crystal growth more complete and reduces the internal defects of the crystal,and the larger grain size also increases the porosity between the columnar crystals,so as to improve the specific capacitance.2)The high energy and low density Ar and Kr plasma were used to etch the HfN coating,to change its surface topography and improve the conductivity of the film,thus improving the electrical and electrochemical properties.After the plasma etching,the capacitance was increases by 8 times,due to the increase in adsorption sites and exhibits excellent cycle life.3)Etching Ni from CrN-Ni film with chemical etching treatment,we got the porous CrN film,and the specific capacitance of the films increased up to 56.5 mF·cm^-2(current density 1.0 mA·cm^-2,0.5 M H₂SO₄ electrolyte).It is about 80 time to the CrN and CrN-Ni films,due to the porous structure and high specific surface area after the Ni was etched.This demonstrates the feasibility of stripping the metal phase to prepare a porous nitride film electrode.But etching also damaged the structure of the coating and reduced cycle life of the coatings.4)As for now,the maximum specific capacitance of MoN coating is 260 mF·cm^-2(at 1.0 mA·cm^-2),with impressive cycle stability,117.3%of the capacitance retention after 80,000 CV cycles,which is better than the common film electrode capacitance.