Preparation Of TiO₂ Thin Films And Research Of Their Memory Properties

With the development of the information society and the huge growth of digital information,the requirements for information storage and computing processing are increasing day by day.Due to the characteristics of memory,low power consumption,high speed,and CMOS compatibility,memristors hold great potential for future storage and neuromorphic computing technologies.Among the materials of memristors,TiO₂ have attracted widespread attention based on their characteristics of stability,non-toxicity,harmlessness,good environmental compatibility and low production costs.TiO₂ thin films synthesized by hydrothermal process is simple,low cost,environmentally friendly,easy to control the morphology,non-polluting,good for mass production,but few people have systematically explored the influence of hydrothermal process factors on the structure,morphology and the memory properties of TiO₂ films.However,TiO₂ memristors still have many problems at present,such as unstable memory properties and inability to achieve large-scale commercial production.Therefore,it is also extremely important to enhance and improve the memory properties of TiO₂ thin films.The following is the contents of this article:（1）TiO₂ nanofilms are prepared on FTO conductive glass through single factor and orthogonal experiments,and the influence of hydrothermal process on the structure and surface morphology of the prepared TiO₂ nanofilm functional layer is explored.Taking the forming voltage as the optimization index,the factors（hydrothermal temperature,the content of tetrabutyl titanate,hydrochloric acid concentration,hydrothermal time）is optimized,and the optimized process parameters is obtained as follows:the hydrothermal temperature is 140°C,the content of tetrabutyl titanate is 0.15 ml,the hydrochloric acid concentration is 7 mol/L,and the hydrothermal time is 4 h.（2）Based on the optimization of hydrothermal process parameters by orthogonal experiment,N-doped TiO₂ nanofilms is prepared by single factor method,and the optimal concentration of N-doped TiO₂ is obtained based on the analysis of characterization results.The experimental results show that when the added ammonia concentration is 2 mol/L,the forming voltage of the device is the lowest,which is 2.3 V.（3）The Au upper electrode is fabricated on the TiO₂ nanofilm prepared under optimized hydrothermal parameters by ion sputtering,and the FTO/TiO₂/Au memory device is successfully fabricated.Its I-V characteristics are analyzed by semiconductor parameter analyzer,and its forming voltage is 2.9 V,the set voltage is 2.5 V,the reset voltage is-3.1 V,and the high-to-low-resistance ratio is 25;at the same time,the FTO/N:TiO₂/Au memory device is successfully prepared.The N-doped device shows a more stable resistance state,and the forming voltage,set voltage,and reset voltage of the FTO/N:TiO₂/Au device is reduced,which is 2.3 V,1.1 V,-1.5 V.Its high-to-low-resistance ratio is 105,which is more than four times that of the undoped device,and it maintains a stable switching voltage over multiple cycles.（4）The conduction mechanisms of FTO/TiO₂/Au and FTO/N:TiO₂/Au devices are analyzed by piecewise linear fitting of their I-V characteristic curves in double logarithmic coordinates.The results show that N doping doesn’t change the conduction mechanisms of the devices.Both of them follow the ohmic conduction mechanism during LRS and the trap-controlled SCLC conduction mechanism during HRS.