Floating Gate Optoelectronic Memory Based On PtS₂/h-BN/Graphene Van Der Waals Multilayers

With the arrival of the era of big data,memory is the key to ensuring that computers have memory functions and can work efficiently.Floating-gate memories play an important role in the long-term storage of data due to their long-term charge retention properties.The two-dimensional floating-gate photoelectric memory has the characteristics of small size,low energy consumption,obvious photovoltaic effect,which contributes to low power consumption,high integration,high switching ratio,and excellent performance for optoelectronic storage.Through a large number of literature and experimental investigations,this paper selects PtS₂ as the channel material,h-BN as the tunneling insulating layer,and graphene as the floating gate layer to fabricate the floating-gate optoelectronic memory.The main research contents are as follows:?1?The van der Waals heterojunction was stacked by mechanically exfoliated single crystal and dry transfer technique.The morphology was observed by optical microscope,Ramma microscope was used to characterize the material properties,TEM was used to characterize the interface of the materials,and the surface potential distribution of the heterojunction was characterized by KPFM.?2?The electrical storage performance of the device was characterized in dark,the transfer characteristic curve tells us that the device can reach an ultra-high on/off ratio upto10⁷ within a gate voltage range of 30 V,and a voltage pulse of 1 ms can achieve the on/off ratio of 10³,which means the device can be written and erased quickly,meanwhile,the on/off ratio has strong gate voltage dependence.The switching ratio can be maintained at around 10⁶ in 1000 s and 1000 erasing cycles when gate voltage pulse applied,indicating that the device has good charge retention performance and durability.?3?By fabricating a tunnel junction device,it was found that illumination facilitates the injection of hot electrons/holes in graphene into PtS₂ through FN tunneling,and the tunneling behavior stronely dependents on wavelength and power density.Therefore,with the combination of voltage and illumination,the threshold voltage of the device can be reduced.By controlling the power density and the number of laser pulse,74 different resistance states?>6 bit?of the device can be achieved,thereby photoelectric multi-level storage is avaliable.