Study On The Stacking Characteristics Of TiO_x Based Resistive Memory And Its Mechanism Analysis

In information age,people increasingly rely on flash-based storage products to store data,but they have the disadvantages that the operating voltage cannot be reduced with the size-down of devices and the charge retention capability is insufficient.Because of a series of advantages(high integration density,fast read/write speed,etc.),the resistive switching random memory has become the focus of research in the academic community.According to the different resistive switching mechanisms,it can be divided into two types:ionic type and electronic type.This thesis is based on electronic type of Al/Ti O_x/Al structure(here after ATA)with electroforming-free.It performed the relationship associated with different interfacial stacking in ATA devices,The aim is that the device maintains the electroforming-free characteristic,and also its endurance and retention can also be improved by stacking process.In this thesis,the electrodes were prepared using electron beam evaporation.The resistive switching layer Ti O_x and the stacked layer Ti O_yare prepared by a multi-functional magnetron sputtering.The chemical valence state of the material is characterized by X-ray photoelectron spectroscopy,and the microscopic condition of the device interface is observed by high-resolution transmission electron microscope.The I-V characteristics and endurance performance of the device were measured by a semiconductor device analyzer.ATA devices that meet electroforming-free were first prepared.Then they inserting the stacked layers in the upper interface,lower interface and both upper and lower interfaces respectively.It was shown that the stacked device has greatly improved its endurance while it meet electroforming-free,and found the optimal stacking process parameters.ATA devices which greatly improve the retention is obtained by testing the devices under the different stacking positions.Subsequently,the optimal test voltage was found by testing stacked devices under optimal stacking conditions at different operating voltages.Under the action of the stacked barrier,changing the operating voltage can make the traps capture and release electrons in a dynamic equilibrium,thereby changing the resistive switching performance of the device.Finally,under the optimal conditions,the I-V curve was double-logged and the device was tested for temperature under different operating voltages to calculate the activation energy values before and after different resistance states and cycles.It proves that the stacked Ti O_yonly acts as a barrier.It also proves that the stacked device meets the space-charge limited current(SCLC)that its resistive switching mechanism is related to the trapping and release of electrons by the trap,and has nothing to do with the movement of oxygen ions.By annealing the ATA lower-level Al air,an Al O_x barrier layer is formed on the lower interface.Further confirms the principle of resistance change of stacked devices.In this thesis,by stacking the interface of the ATA structure device and changing the operating voltage,the stacked device meets electroforming-free,and its endurance and retention were also improved.The principle of resistive switching is analyzed.This work can help people to further understand the electronic resistive switching mechanism,and at the same time provide a certain reference for the preparation process of electronic devices.