Floating Gate Transistor Non-volatile Memory Based On Core-shell Semiconductor Quantum Dots

With the development of digital and network technology,human society has stepped into the information era since 21 st century.The pervasiveness of information technologies is generating huge amount of data,which need to be stored and accessed very quickly.Therefore,tremendous efforts focus on the investigation of new types of memory which own nonvolatile capability,high-density storage,fast access speed,and reliable endurance property.In the category of nonvolatile memory,the floating gate transistor-based nonvolatile memory,which owns some advantages such as compact structure,nondestructive readout property,and facility to be integrated with complementary metal-oxide-semiconductor(CMOS)technology,has become the mainstream in the nonvolatile memory market.However,due to the unceasing increase of the integration level of semiconductor devices,and the emergence of new requirements for nonvolatile memory following the development of information technology,traditional floating gate memories is facing severe challenges.The research on new nonvolatile memories is impending.In this dissertation,floating gate transistors based on ZnSe/ZnS core-shell quantum dots are studied,in terms of the quantum dot structure,surface modification ligand,deposition density,and transistor insulating dielectric layer.The results of the physical mechanism study clarify the motion of the charge in the device information storage process,providing a technical and theoretical knowledge reserve for the construction of high-performance non-volatile memory.The main research contents and results are as follows:The first part of this dissertation explores that different types of quantum dots(ZnSe @ ZnS-OA QDs,ZnSe @ ZnS-MPA QDs,ZnSe-OA QDs,ZnSe-MPA QDs)are used as charge trapping layers of floating gate transistor memories.The experimental results show that the device based on ZnSe @ ZnS-OA QDs has a memory window of up to 149 V,120 stable continuous writing/erasing,and a data retention rate of more than 55% in 10 years,which shows good device performance.By comparing four different quantum dots,it is found that the ZnSe core plays the role of a charge-trapping center in ZnSe @ ZnS-OA QDs.The ZnS shell forms a type-I energy band structure with the ZnSe core.The surface OA ligand has an insulative long chain.The ZnS shell and surface OA ligand act as the charge-tunneling layer,to effectively block the spontaneous recovery and allow for the intentional tunneling of charges.Based on the above experiments,the graphene photo-electric floating gate transistor non-volatile memory was designed.which the ZnSe@ZnS-OA QDs as the discrete charge-trapping/tunneling centers and organic ferroelectric high dielectric constant material P(VDF-TrFE-CFE)as the insulating dielectric layer The storage characteristics of two different modes were studied: electrical storage/electrical erasure and electrical storage/optical erasure.The device realizes a memory window of 63.4 V at an operating voltage of 50 V.The larger memory window can not only realize multi-level memory state,but also in the experiment of multi-level storage,after each electrical write operation is completed.A light illuminating device can be used to erase the electrical write state,enabling a light resettable low power erase operation.In addition,the device exhibits excellent non-volatility,is expected to have more than 10 years of data retention,reliable cycling endurance over 100 cycles,and the use of an organic high-k dielectric layer reduces operating voltage.This study reveals the huge potential of core-shell semiconductor quantum dots in floating gate transistor non-volatile memory,paving a promising path for this type of device.