Fabrication And Properties Of TiN Based Nanocapacitor

Electrolytic capacitor has been ignored for many years due to its low energy density.However,its power density is much higher than those of other energy storage devices,such as supercapacitor and cell.The organization of nanostructures in supercapacitor is an effective way to enhance its energy density.As the energy-storage mechanisms for both supercapacitors and electrolytic capacitors only involve surface charge,it is possible to enhance the energy density of electrolytic capacitors by the organization of nanostructures.First of all,TiN nanotubes are fabricated by annealing anodic TiO2 nanotubes in ammonia atmosphere.The annealing parameters(temperature,time and heating rate)are investigated to optimize the annealing process.The results show that N-doped TiO2 nanotubes can be prepared when the annealing temperature is lower than 800℃ and TiN nanotubes can be fabricated when the annealing temperature reaches 800℃.When the annealing temperature is up to 850℃,the wall of nanotubes is much thinner.The longer annealing time contributes to higher conversion rate and rougher nanotubes.The faster heating rate avoids the generation of N-doped TiO2 nanotubes but leads to the damage of nanotube structure.Secondly,the anodization of TiN nanotubes in 5 wt%NH4B5O8 and 1 wt%H3BO3 aqueous solution is conducted to fabricate TiO2 dielectric film.The anodization parameters(voltage,temperature and time)are studied in detail.When the applied voltage reaches 6 V,the tube wall of TiN nanotubes has been totally transformed into compact TiO2 film.Then,TiN nanorods can be prepared by solid-gas interface reaction of as-anodized TiO2 nanotubes and subsequent nitridation through ammonia annealing.When the solid-gas interface reaction time is more than 40 min,TiN nanorods can be obtained.The anodization of TiN nanorods is performed to fabricate TiO2 dielectric film.The nanostructure of TiN nanorods can avoid the excessive anodization of TiN effectively.The results demonstrate that the samples with solid-gas interface reaction time of 50 min yield the highest capacitance.And the second anodization of the TiO2 dielectric film can decrease the leakage current of the dielectric film.Finally,BaTiO3 dielectric film is fabricated by hydrothermal conversion of compact TiO2 film.The concentration of KOH and hydrothermal time are studied in detail.The highest capacitance of BaTiO3 dielectric film is up to 6.88 μF cm-2,well above that of TiO2 dielectric film.