Preparation And Performance Study Of MoS₂ Heterojunction Photodetector Based On Surface Plasmon

Transition metal dichalcogenides（TMDs）materials of MoS₂ class have become one of the potential material types in the field of optoelectronic detection due to their advantages such as fast photoelectric conversion speed,small size,and low power consumption.Van der Waals heterojunctions can be formed by selecting ultra-thin TMDs with different band characteristics and using precise transfer stacking methods.The special band structure constructed provides feasibility for achieving integrated precision photoelectric detection,high sensitivity and wide spectral detection,and is one of the hotspots in international research today.However,due to the fact that the thickness of MoS₂ type ultra-thin materials is only on the atomic level,they exhibit a low light absorption rate,which leads to fatal problems such as the photoelectric conversion efficiency,slow response speed,and large dark current flow of corresponding devices,severely limiting their potential for further application in the field of optoelectronic detection.As is well known,surface plasmon effect is an electromagnetic mode formed by the interaction between electrons and photons in the interface region of micro/nano metal structures and media.When this effect is combined with semiconductor materials,the electromagnetic field is limited to a small range on the metal surface and strengthened.In response to the aforementioned issues,this work focuses on the MoS₂ heterojunction modified by gold nanoparticles.By exciting the local surface plasmons of gold nanoparticles,the light absorption of the device is increased,thereby improving the photoelectric detection performance of the device.Exploring the effects of the density,size,and preparation process of gold nanoparticle layers on the interface localized electric field,carrier generation,and transport in MoS₂ heterojunctions from two aspects:simulation model calculation and device preparation and testing.Based on the above ideas,this thesis calculates and selects P-type semiconductor material Mo Te₂ with a bandgap of 0.8 e V and N-type semiconductor material MoS₂ with a bandgap of 1.2 e V to stack,forming a heterojunction with a barrier height of 0.3 e V and a type II band structure.By combining FDTD and COMSOL software with simulation,calculations have shown that MoS₂ and Mo Te₂ exhibit an incident light intensity of 0.4～1μm and the maximum light absorption rate in the range is 0.4.After introducing gold nanoparticles with micro/nano structures,the light absorption rate of MoS₂/Mo Te₂/gold nanoparticles composite structure increased to over 0.8 under 400 nm illumination,and it was demonstrated that when the distance between gold nanoparticles was smaller than their diameter,strong local electric fields were excited between gold nanoparticles and between gold nanoparticles and MoS₂.Based on the above simulation results,gold nanoparticles modified MoS₂/Mo Te₂ van der Waals heterojunctions were prepared using techniques such as laser direct lithography,precise stacking of two-dimensional materials,and capillary effect assembly.The experimental results show that the MoS₂/Mo Te₂heterojunction,modified with gold particles with a diameter of 160 nm,can obtain a photocurrent of 10^-4 A under incident light irradiation at a wavelength of 405 nm,and achieve a maximum response rate of 2771 A/W at a wavelength of 520 nm.The response time of the device can reach as fast as 1.85 ms and maintain a stable current output after100 periods of switching response.The above results indicate that the localized strong electric field generated by gold nanoparticles and the hot electrons on them can significantly improve the photoresponsivity and photocurrent of MoS₂/Mo Te₂heterojunctions,while maintaining ultra-high stability.This result is also consistent with the simulation calculation results of light absorption rate.