Study On The Resistive Switching Characteristic And Mechanism Of CH₃NH₃PbI₃ Films

Resistive switching access memory is one of the most promising candidates for the next generation non-volatile memory,which attracting strong interest at present.The RRAM consist of a resistive switching thin film sandwiched between two electrodes.Since the properties of the materials plays an important role in the performance of RRAM,the focus research is also the development?design and regulation of material system in the field of RRAM.Though there is no exact conclusion about the microphysical mechanism of the switching phenomenon,it is widely believe that the resistive switching?RS?mechanism usually can be attributed to the migration of the ions in the resistive switching thin film drived by electronic field.Recently,hybrid organic-inorganic perovskite has show the potential for the application in the fields of RRAM duo to the the migration of the ions in the thin film in addition to the excellent photoelectric properties.This provides the possibility for the RRAM to develop new optoelectronic bonding features.Our works are mainly on the controllability and investigation of the mechanism of the RS behavior in hybrid perovskite RRAM devices.The thesis contains as follows:1.On the controlliabity of the RS characteristic:?i?For the Au/CH₃NH₃PbI₃/FTO memory device,bipolar RS behaviors and negative differential resistance?NDR?behaviors were demonstrated by controlling the deposition conditions of the film;?ii?Different types of the conductive filament can be realized bu utilizing different electrodes?Au?Al?Ag?,since they possess different electrochemical activity.For the Ag/CH₃NH₃PbI₃/FTO memory device,nonvolatile/volatile RS behaviors were demonstrated by controlling the CC?that is,the size of Ag channel?.For the Al/CH₃NH₃PbI₃/FTO memory device,due to the random nature of the formation and rupture of iodine conductive channel,the large fluctuations of switching parameter remain obstacle for the RRAM practical memory applications.The uniformity is improved under illumination by reducing forming voltage,in turn reduce the randomness of the formation of iodine conductive channel,which provide uniformity of switching properties.2.On the controlliabity of the interface state and investigation of the mechanism of the NDR behavior: we study the influence of interface-state on the RS behavior of an Au/CH₃NH₃PbI₃/FTO memory device which using a simple air-exposure method.We observe a transition of RS hysteresis behavior with exposure time.Initially no hysteresis is apparent but air exposure induces bipolar RS and a negative differential resistance?NDR?phenomenon.The reductions of I/Pb atomic ratio and work function on film surface are examined usingXPS spectra and Kelvin Probe technique,verifying the produce of donor-type interface-states?e.g.iodine vacancies?during CH₃NH₃PbI₃ film degradation.Studies on complex impedance spectroscopy confirm the responsibility of interface-states in NDR behavior.Eventually,the trapping/de-trapping of electrons in bulk defects and at interface-states accounts for the bipolar RS behavior accompanied with NDR effect.3.On the study of endurance failure mechanism: the cycling induced degradation of Al/CH₃NH₃PbI₃/FTO memory device was studied,utilizing the change of iodine conductive channel.By studying the negative set behavior,it is concluded that the primary cause of failure is the increase of internal defect density.The degradation with cycling is attributed to the increasing of the defects in the CH₃NH₃PbI₃ film due to?1?the loss of iodine within the active filament area in the RRAM device and?2?the decompose of the film by joule-heating.