Fabrication And Characterization Of Resistive Memories Based On Quantum Dots

Semiconductor memory is not only one of the most basic components of electronic equipment but also an important part of modern information technology.Currently,flash memory as the most popular memory is starting to face the development bottleneck that the size is difficult to continue to shrink.To solve this problem,scientists have conducted a lot of research on the next-generation non-volatile memory,including magnetic memory devices,ferroelectric memory devices,phase change memory devices,and resistive memory devices.With the development of network technology,computer technology and various popular consumer electronic products,the demand for non-volatile memory is increasing.Traditional memory devices are faced with some problems such as low storage density,high processing cost,and complicated device preparation processes,which cannot meet future development needs.RRAM can realize the resistance conversion between the high and low resistance states operated under a certain voltage between the electrodes.Comparing with other non-volatile memories,RRAM has some advantages such as simple structure,fast operation speed,low power consumption,and the potential to continue to shrink in size.At the same time,it has a very big advantage in maintaining characteristics and data storage.And it is compatible with the current CMOS process.The above indicates that it is regarded as the most promising high-density non-volatile memory of the next generation.The structure of the RRAM device is a typical three-layer structure of electrodes/materials/electrodes.Resistive conversion effects have been found in metal oxides,metal sulfides,organics,and perovskite oxides.The dimension of the resistive memory materials can be divided into one-dimension,two-dimension and three-dimension.Compared to high-dimensional materials,low-dimensional materials have characteristics such as small particle size.The newly developed semiconductor material AgInZnS has potential application prospects in the field of optoelectronics due to its simple,non-toxic and rich synthetic methods.Graphene quantum dots overcome the phenomenon of stacking and aggregation caused by strong intermolecular forces between graphene sheets.At the same time,it possesses the excellent properties of graphene and quantum dots,making it more attractive in chemical,biological,medical,optoelectronic and energy related fields.In this article,AgInZnS quantum dots,graphene quantum dots and PMMA composites are used as the resistive change active layer,which are spin-coated on a transparent ITO conductive glass.Then the electrodes are evaporated to form Al/AgInZnS/ITO and Ag/GQDs & PMMA/ITO structures.The preparation of the materials and the devices,the resistance behavior and the corresponding mechanism of resistance change are analyzed and studied in depth.Based on the excellent performance of these materials and devices,the following research works have been done in this paper:In the first chapter,we reviewed several important new types of nonvolatile resistors,introduced the development history,research status,and some basic information of the resistor,And then we introduced the basic properties of quantum dots,and the important significance and the content of this thesis.In the second chapter,the preparation methods of AgInZnS quantum dots,graphene quantum dots and their resistance switching devices are introduced.The materials were spin-coated on a transparent ITO glass as an active layer,and the upper electrode was vapor-deposited to construct a resistive switching device.The structure,morphology,and the optical properties of the materials are analyzed.The characterization methods of the electrical properties of the resistive switching devices are introduced.The third chapter introduces the research of RRAM devices based on the AgInZnS quantum dots.The synthesized AgInZnS QDs were characterized by TEM,XRD,Abs and PL spectra.The fabricated Al/AgInZnS/ITO device was tested for electrical properties.The I-V curves shows that the device has bipolar resistive properties.The device's switching current ratio is 18,which has good stability,long retention time and fast response.Finally,through the theoretical simulation of I-V curve,We explore its storage mechanism.The fourth chapter introduces the research RRAM devices on graphene quantum dot.The morphologies,structures and optical properties of graphene quantum dots were systematically characterized.In order to investigate the role of graphene quantum dots in the resistor,the graphene quantum dots were composited with PMMA and the memory device Ag/GQDs & PMMA/ITO was prepared with the composite as the active layer.By comparing the resistive device of Ag/PMMA/ITO,We found that the resistive device of Ag/GQDs & PMMA/ITO has a lower operating voltage and better resistance to change.Finally,through the theoretical simulation of I-V curve,we explore their storage mechanisms.The fifth chapter summarizes the research work of this paper,and points out the advantages of the above materials,and looks forward to the development of resistors based on new materials.