Study On The Oxygen-defective RRAM Regulated By Introducing Carbon Quantum Dots

With the development of electronic technology,the traditional Flash memory will suffer from performance degradation as the scaling limit is approached.In the order to achieve high-density data storage in the future,new generation non-volatile memories have been proposed one after another.Among them,resistive random access memory?RRAM?,which is a promising technology for next-generation nonvolatile storage,is attracting growing interest owing to its simple sandwich structure of metal/insulator/metal,low power consumption and high-density integration.To date,although the resistive switching?RS?mechanism has not been conclusive,it is usually attributed to the migration of metal cations and oxygen defects,which will result in the formation and dissolution of conductive channel in the RS layer.However,the randomness of the formation the location,morphology and size of the conductive channel is still not solved,leading to significant reliability issues,e.g.,issues with data retention time and fluctuation of RS parameters.Therefore,the randomness of conductive channel formation can be effectively regulated has become the core topic in this field.Our works mainly aim at the key issues of RRAM based on graphene oxide?GO?and hafnium oxide(HfO_2-x),making some regulations by unique properties of carbon quantum dots?CQDs?for RS behaviors and exploring the RS mechanism,and expand the application of RRAM in multi-functional devices.1.The surface property of the carbon quantum dots is used to regulate the oxygen functional group migration barrier in GO materials to improve the retention characteristics of small-sized conductive channels.?i?We have investigated the main cause of the volatile phenomenon in the RS processs.The conclusion that the retention time of RRAM has a specific dependence on the size of the conductive channel is clarified.?ii?The effect of the level of the migration barrier of the oxygen functional on retention characteristics of the low resistance state?LRS?was investigated by adjusting the sp²/sp³ ratio of CQDs.?iii?The level of migration barrier in the GO film is further optimized,which eliminates the volatile phenomenon in the RS process,improves the retention characteristics of LRS and exhibits the excellent RS reliability.2.The photoelectric property of the CQDs is used to regulate the size of sp² clusters in GO film.This result shows that the electric field is localized,which improves the RS uniformity of the GO-based RRAM.The size of sp² clusters in GO film controlled by UV-light technology using the photocatalytic property of the nitrogen-doped CQDs.Further,the sp² clusters size in the GO film is optimized by effectively controlling the UV-light irradiation time to improve RS uniformity.The XPS and Raman results further demonstrate the feasibility of photocatalytic reaction to regulated sp² clusters size.In addition,the mild photoreduction method can be extended to the application of carbon-based flexible RRAM.3.The dimensional property of the CQDs is used to construct the conductive tips in HfO_2-x interface.The RRAM was improved to achieve excellent reliability by the local electric field enhanced,and realize that the multi-level RRAM by tuning the size of conductive channel.We further developed a modulated light-emitting device?LED?by integration of a p-GaN/n-ZnO heterojunction with multilevel RRAM.Eventually,the reversible regulation of electroluminescence intensity was demonstrated by tuning the compliance current in the modulated LED.Furthermore,our work also opens a new way to developing RRAM devices integrated with other functional electronics.