| The memristor,which is the basic element of the fourth circuit,has the advantages of simple structure,fast reading and writing,low energy consumption,and high storage density,and is expected to break through the limits of Moore'Law.Analog the neuromorphic computing and the logical operations with the digital state are two ways for memristors to realize the fusion of the information storage and computing.Although the research on memristors has exploded,it is still in its infancy.There are still many unresolved problems in memristive materials,analog tunability,resistance switching mechanism,energy saving,reliability,heterogeneous integration and multi-functional realization.Therefore,the development of new memristive materials,multi-channel exploration of resistance switching mechanisms,clarification of parameter evolution rules,and on this basis to expand the functions(such as:synapses,number recognition and logical functions,etc.),is the urgent research work that needs to be carried out at the moment.Two-dimensional(2D)layered materials have broad application prospects in the fields of energy conversion and storage,and electronic devices,due to its unique and adjustable electronic structure,rich physical and chemical properties.In this work,Sn Se and other 2D layered materials were took as the research object,and explored for new applications in the field of memristors from the aspects of preparation process,physical mechanism,performance characteristics and function realization of photoelectric control.The main research contents are as follows:1.A high-quality Sn Se thin film was fabricated by pulsed laser deposition technology and a prototype memristive device with Au/Sn Se/NSTO(7%Nb:Sr Ti O3)structure was constructed with the help of mask technology.The experimental results verified the ferroelectricity of Sn Se material.Because the ferroelectric polarization can modulate the width of the depletion layer and the height of the barrier in the junction region of the device,the memristor can achieve precise adjustment of conductance and the second-order memristive behavior.A stimulus pulse with a nanosecond pulse duration was applied to the device,and successfully simulated two synaptic behaviors,spike timing-dependent plasticity(STDP)and paired-pulse facilitation(PPF),with an energy consumption of only 66 f J.In addition,the device can also realize handwritten digit recognition with an accuracy of 82.51%.2.Based on the above work,the memristor with Pd/Sn1-xSe/NSTO and Ag/Sn1-xSe/NSTO structures were fabricated.The overall performance of the Pd/Sn1-xSe/NSTO memristor is better than that of common devices,especially the stability,the difference between the memristor cells,the durability,and the ON/OFF power can reach about 4.1?W and 61?W.Using first-principles calculations,the possibility of palladium(Pd)conductive filaments formation and destruction in the Sn1-xSe film was predicted.And the Pd conductive filaments in the Sn1-xSe layer were observed directly by using the high-resolution transmission electron microscope and X-ray energy dispersive spectrometer analyzer.Metal Pd has higher thermodynamic stability and lower mobility than silver(Ag),so the device performance based on the Pd filaments mechanism is more stable.In addition to realizing synaptic functions,the device can also realize simple counting and addition operations.3.The double-terminal Au/Sn Se/graphene/Si O2/Si and Ti/Bi OI/FTO(Sn O2:F)memristive devices were fabricated by a variety of thin film deposition processes.The introduction of multilayer 2D graphene enables the ON/OFF power of Sn Se-based memristors to reach 16.7n W and 2.3 n W.Through the transmission electron microscope and XPS in-depth analysis,comparing the element distribution of the device at the high-resistance state and the low-resistance state,it is confirmed that the resistance switching mechanism of the above-mentioned two types of memristors are derived from the formation and fracture of Sn vacancy and oxygen vacancy filaments.The memristors based on the vacancy filament mechanism can simulate the long-term potentiation(LTP)and long-term deression(LTD)of bio-synapses,and complete the learning and memory rules of STDP and PPF.4.A large-area multilayer 2D Bi2Te2.7Se0.3 film and a Pd/Bi2Te2.7Se0.3/Si O2/Si multifunctional photoelectric coupling device was fabricated by using PLD technology.The405 nm wavelength violet light signal with four intensities of 0 m W,5 m W,50 m W and 100m W,and the electrical signal was used to study the internal conductivity adjustment of the device.The device can not only realize the“OR”logic function,but also realize long-term storage of information due to the non-volatility of photoelectron recapture;meanwhile,the resistance of the photoelectric coupling device has a certain dependence on the light intensity,so that it can realize the functions of multi-level storage and the optical information demodulation.In short,the single memristive device can simultaneously realize the functions of demodulation,calculation and storage. |
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