Photoelectronic And Storage Performance Of Two-Dimensional MoS₂/ZnPc Inorganic/Organic Heterostructures

Two-dimensional transition metal dichalcogenides?TMDs?with layer-dependent electronic band structure and easy assembly are finding increasing interest.As a prominent member in the TMDs family,MoS₂ possesses a visible band gap of 1.2-1.9 eV and excellent optoelectronic properties are widely used in the research of functional devices such as photodetectors,transistors,memory and logic ciruit devices.However,the charge traping caused by the defect state,leading to the persistent photoconductance?PPC?that seriously hinders its practical application.In recent years,a large number of studies have shown that resonably designed two-dimensional heterojunction interface can not only improve the properties of TMDs-based devices,but also realize novel functions and expand their application fields.In this context,we prepared the MoS₂/ZnPc inorganic/organic van der Waals heterojunction by combing the organic planar small molecule zinc phthalocyanine?ZnPc?with MoS₂,and explored its photoelectronic and storage performance by using different defect charge trapping effect systematically.The main research contents and results list as follows:1.The MoS₂/ZnPc heterojunction was prepared based on chemical vapor deposition CVD-grown monolayer MoS₂ and the assembly of ZnPc molecules onto the surface of MoS₂ device by a simple liquid phase immersion methond.The photoelectronic properties and the impact of ZnPc molecules on the photoresponse mechanism in MoS₂ detectors were revealed clearly.The results show that the formed MoS₂/ZnPc van der Waals interface is found to instantly separate photogenerated holes in MoS₂ toward the ZnPc molecules,away from the traps commonly found in itself and the dielectric interface,thereby significantly improved response speed of the device to ms level,which is 3 orders of magnitude higher than the MoS₂ alone.The derived MoS₂ detector then exhibits a high responsivity of 430A/W after Al₂O₃ as surface passivation layer,realizing the construction of high-performance MoS₂ based photodetection with ultrafast speed and high sensitivity.2.We fabricated MoS₂/ZnPc heterostructure by the above method based on few layers of MoS₂ which obtained by mechanical exfoliation and carried out comparative study.It was found that the fast response performance decreased with the increase of MoS₂thickness.By using the depletion effect of p-type ZnPc molecules on the surface of it,the channel conductance can be restricted near the MoS₂/SiO₂ interface,thus enhancing the interface defect trapping effect under the regulation of back-gate field effect,and exploring its storage characteristics accordingly.By applying a back gate voltage,deep level defects of the interface state with the substrate are filled or released,thereby greatly changing the MoS₂ channel conductance.This heterojunction device exhibits excellent memory performance,including large memory window?⁶3 V?,high on/off ratio?10⁵?and excellent cycling endurance?10³ cycles?.Finally,we further explored the possibility of using this device configuration to mimic biological neurons,initially achieving synaptic short-term plasticity?STP?and long-term plasticity?LTP?behavior,including inhibitory postsynaptic current?IPSC?,paired pulse suppression?PPD?and other characteristics.The above results indicate that the method based on ZnPc molecular modification can improve the performance of MoS₂ functional devices,which has promising research value in the field of optoelectronics and microelectronic devices.