The Sol-gel Method Prepared SnO₂Memristor And Performance Study

Because of the limitations of the charge storage mechanism, Flash memory, whichbased on charge storage mechanism, is about to reach its theoretical size limit （22nm）.Therefore，it is very necessary to find a novel alternative memory, which process much morespecific merits and without size restriction. In recent years, some new type non-volatilememories emerges, including PCM（Phase Change Memory）, MRAM（Magnetic RandomAccess Memory）, FRAM（Ferroelectric Random Access Memory）, and RRAM（ResistiveRandom Access Memory）. However, the application of the former three emerging memorieshave been suffered from limitation because of the nearly mA class read and write current,low compatibility with CMOS, and the severe dependence on Curie temperature,respectively. Instead, the RRAM has come to the fore, because it has a simple structure, lowcost, low power consumption, high read and write speed and can be reduced to tens ofnanometers. It is based on these advantages, sol-gel annealing sintering method was used toprepare SnO₂resistive layer, and mask-covering deposition method were used to preparecolumnar Al electrode. Finally, the Al/SnO₂/FTO structure resistive memory was obtained.A systematical analysis was conducted to test and characterize the memristor. Additionally,Mn and Sb were added in resistive layer. A systematic comparison and analysis wasconducted on the doped and undoped devices. The main contents are as follows:（1） At first SnCl4·5H₂0, C₂H₅OH, citric acid, etc, were used to configure the precursorsol. Subsequently, a spin-coating and sintering method were employed to prepare theterminal SnO₂film. Then magnetron sputtering deposition technique was used to form theAl top electrode. Eventually Al/SnO₂/FTO memristor were obtained. Furthermore, Mn andSb were added into the SnO₂sol, respectively. And the same preparing method was utilizedto gain the corresponding resistive layer and memristor devices. XRD, SEM, AFM wereadopted to characterize the doped and undoped devices. It is found that, the undoped anddoped films were polycrystalline nano thin film, and the crystal structure was the typicalrutile structure. The obtained film has compactly and uniformity nano-grains, the thicknessof the film has20～45nm undulation. The introduced doping element did not change thecrystalline structure of the original undoped film, and no impurity phases. Mn and Sb played a beneficial role in refining the grain size of the resistive film. The difference is that Mninhibited the crystallinity of the film, while the Sb is the opposite. The photoluminescencetest proved that the oxygen vacancy defects existed in both doped and undoped SnO₂film.（2） The I-V curve and impedance maintain curve was conducted on the doped andundoped Al/SnO₂/FTO memristor, respectively. The results are as follows: To the undopeddevice, the impedance state switch ratio was very small, less than100. The reproducibility ofthe switching process of the memristor was poor, and the reset voltage was relatively high.As the doped devices, the doping of Mn and Sb has greatly improved switch ratio and whatwere over than1000and5×104, respectively. The reduplicate switching stability was alsoimproved after doping. In addition, the reset voltage was significantly reduced. Throughanalysis, these phenomenon were possibly depend on the doped element which inducedelectro-chemical redox on the interface of Al/SnO₂. With the role of both the interface redoxand filaments effect within the resistive layer, the reset voltage was declined. However, theswitch ratio of the Sb doped memrsitor is two orders higher than the Mn doped one. Thismay be ascribed to the multivalent of Mn element and mismatch of the lattice after doping.Finally, the results of the experiment were described at length in turns, and the relatedphenomena were explained rationally. We proposed a number of inadequacies, and alsomake some prospects for the future explore.