Research On Fabrication Of Two-dimensional Ferroelectric Device And Their Photoelectric Property

In order to cope with the exponential growth of the demand for data operation in the era of big data,structure simplification and function integration have become the main trends of the development of electronic information technology in the post-Moore era.Among them,photoelectric storage devices can realize the integration and diversification of information processing functions through the regulation of optical and electrical device resistance,which is conducive to increasing the functional density of devices and realizing the parallel transmission and calculation of data,and is an important direction of future storage development.The current mainstream flash memory is not enough to adapt to the current development route.In contrast,two-dimensional ferroelectric memory has the advantages of fast read and write speed,non-volatile,anti-radiation and high integration,so two-dimensional ferroelectric memory device is a better solution for memory.However,at present,ferroelectric memory devices based on two-dimensional optical control still have shortcomings such as small switch,so the theory is not perfect.Based on the above requirements and problems,the photoelectric multistate memory device is successfully fabricated by optimizing the characteristics of channel layer and ferroelectric layer Cu In P₂S₆,which shows the potential of high-density photoelectric storage and synaptic simulation.This thesis further studies the operating principle and law of the device on this basis.The details are as follows:1.The ferroelectric storage transistor with Cu In P₂S₆ as ferroelectric dielectric layer and Mo S₂ as channel was prepared by dry transfer and photolithography mask method.Firstly,we use high temperature annealing（360℃,1 h）to reduce the adsorption of water oxygen at the interface and remove the bad contact at the interface,thus reducing the contact resistance and improving the working current of the device.By optimizing the thickness of Mo S₂ and Cu In P₂S₆,the channel current-carrying concentration is adjusted,and the threshold voltage and storage window are further regulated.The optimized device（channel thickness is less than 5 layers）shows a storage window of 3 V,a switching ratio of more than 10⁶,a storage time of more than 4000 s,and can realize multistate storage regulated by write voltage.2.A method is proposed to study the working principle of two-dimensional ferroelectric memory devices by using the direction of photovoltaic voltage to characterize the direction of polarization.In this method,we find that the channel of the device is mainly regulated by Cu ions migrating to the interlayer under low voltage,and when the ferroelectric voltage at both ends is higher than the coercive field,the ferroelectric polarization field and the ion migration field regulate the channel together.3.Discover the multistage resistance state of ferroelectric storage transistor regulated by light,and reveal the two working state principles of the device under low voltage write"optical write"and"electric write optical wipe".There is a positive linear relationship between the increase of optical power and the speed of optical writing and erasure.With the light pulse of 2 s width,230 different resistance states can be obtained,and can remain stable,the rate of change is less than 0.009%.