| Resistance random access memory(RRAM)is the nonvolatile memory which based on the semiconductor characteristics of thin film materials,which can realize the high resistance and low resistance states repeatable conversion under the action of electric field.TiO2 has lots of merits such as high dielectric constant,the advantages of high ion conductivity and it is widely used for RRAM research.Nowadays,glass,silicon and other rigid substrates are used as the base for TiO2 films.Few researches are studied in flexible TiO2 films.In this paper,the TiO2 nanoparticles were prepared by hydrothermal method,and the TiO2 and its composite film were preparation on the PET flexible substrate by spin coating method.We study the bending effect on the switching performance of the film,and analysis the switching mechanism.Firstly,the TiO2 nanoparticles were prepared by hydrothermal method.We study the influence of hydrothermal temperature and time on the TiO2 nanoparticles and find that the nanoparticles got by hydrothermal growth at 160? for 2h have the best performance.Its side is about 10nm.When the films were prepared on ITO/glass substrates,their ON/OFF ratio were about 103 and the threshold voltage of films were about 2.1V.The high resistance state currents show space charge limited conduction phenomenon and the switching mechanism can be attributed to the forming/breakage of the oxygen vacancies filamentary paths.We made the film by spin coating on the ITO/PET substrate.After clamping,the size of the substrate is 15 cm×40 cm.We definite that when the film isn't bent,twisting distance is 40 cm.When the bending distances were 25cm,after bending 1000 times,the threshold voltage increase from 1.4V to 1.8V and the ON/OFF ratio decline from 2552 to 349.When the bending times were 500 times,the resistive characteristics of the films declined fastly with the reducing of the bending distances.When the bending distances were 20cm,the thin films had been destroyed and didn't had resistance characteristics.After bending,there are lots of drapes even breakages in the film.The films slipped away from the substrate and the resistive characteristics of the films declined fastly.When spin coating numbers were 2-3 layers,thin film had good resistance characteristics after bending,but when the spin coating number increased to 5-6 layers,bending resistance characteristics of thin films decreased obviously.The reason is that with the increasing of thickness,films are more likely to be damaged during the bending.Secondly,the TiO2,CuO and TiO2-CuO chemical composite nanoparticles were prepared by hydrothermal method,and mixed the TiO2and CuO nanoparticles with different Ti-Cu ratio.The ON/OFF ratio of the mixture films were declined,but the chemical composite film were increased.The reason is that the p-n interface and tunneling barrier are forming when TiO2 and CuO nanoparticles were mixed.They prevent the injection of the carrier,which make the ON/OFF ratio of the switching devices decline.However,when we made TiO2-CuO chemical composite nanoparticles,there were some TiCuO,generated,which has good electrical conductivity.They reduce the release barrier of the capture electronic,and the ON/OFF ratio increase.We do some outside and inside bending research on the film which was made by the mixed and the chemical composite nanoparticles with 1:1 Ti-Cu ratio to find out the influence of the bending on the resistive characteristics of the composite flexible film.We find that the mixed nanoparticles don't improve the resistive characteristics and resistance to bending properties,but the chemical composite nanoparticles get it.When the Ti/CuO was mixed,after bending 1000 times,the threshold voltage increase from 2V to 3V and the ON/OFF ratio decline from 614 to 68.However,after bending 2000 times,the threshold voltage of the chemical composite nanoparticles films increase from 2V to 2.7V and the ON/OFF ratio decline from 3048 to 150.The reason is that when the Ti/CuO was mixed,the film didn't mix uniformly and there were lots of defects in the film.When chemical compositing,the TiO2-CuO compound was formed and its resistive characteristics improve.Finally,we study the torsion influence on the resistive of the TiO2 nanoparticles film and chemical composite nanoparticles film with 1:1 Ti-Cu ratio and find that the damage to the film is far higher when torsion than bending.After 200 times bending,the ON/OFF ratio of the TiO2 nanoparticles films decline from 2552 to 186.Resistive characteristics of the chemical composite nanoparticles were declined fastly after 500 times bending.The destruction of the shear stress on the film which generate from torsional experiments are much larger than tensile damage to the film. |
PDF Full Text Request