Preparation And Electrochemical Properties Of High Specific Capacitance TiN Films

Since the beginning of 21st century,with the continuous efforts human made in the fields of biological science and energy science,there has been many breakthroughs.For sequencing technology,the biochips have been manufactured.For energy storage,micro supercapacitors have been discussed.However,there are still a lot of problems to be solved.To find electrode materials with high specific capacitance,long cycle life and good compatibility is one of the most important problems among them.Some patents and researches have pointed out that sputtered TiN films have potential to be the working electrodes in the above device.In this paper,the preparation of TiN films will be carried out by RF and DC magnetron sputtering.K9 glass is chosen to be substrate and there is no current collector between substrate and TiN thin film.During RF sputtering,sputtering power and corrosion of HF acid on the substrate are main points to be discussed.In this part,the microscopic and electrochemical properties of TiN films are investigated.During DC sputtering,two variables which contained working pressure and corrosion of the substrate by HF acid are mainly studied.Microscopic test,square resistance and electrochemical test are taken to the samples.Among them,microscopic analysis includes XRD,XPS and AFM,which mainly studies the preferred orientation,elemental composition and surface roughness of TiN films.The square resistance test is mainly used to calculate the resistivity of the film.Electrochemical tests include cyclic voltammetry(CV),constant current charge and discharge(GCD)and alternating current impedance spectroscopy(EIS),which are mainly used to analyze the specific capacitance of TiN films.The experimental results show that the TiN film prepared by RF magnetron sputtering contains three preferred orientations.The O content of the film surface is low and the roughness of surface is small.The square resistance test showed that the conductivity of the film is good.However,the specific capacitance is very low.The maximum specific capacitance is only 0.5 mF/cm~2.For the DC samples,as the working pressure increases,the preferred orientation of the film changes,the internal O content gradually increases,and the surface roughness of the film becomes larger.Square resistance test shows the resistivity of the samples gradually increases.The specific capacitance value tested by electrochemical test also increases while the rate performance becomes poor.Cyclic test shows that the cycle life of DC TiN film is better.After 270 cycles of cyclic charge and discharge under the condition of current at 0.2 mA,the specific capacitance is maintained at about 94%.Analysis of the obtained data reveales that the reason for the high specific capacitance value of the DC sputtering sample is the result of chemical adsorption and desorption between Ti-O-N structure and K~+in the electrolyte.For DC samples,the corrosion of substrate has small effects on specific capacitance.