Preparation Of Two-dimensional TiSe₂/TiO₂ Heterostructures By Laser Irradiation And Study On The Photo-electrical Behaviors

TiSe₂ is a member of the two-dimensional layered transition metal chalcogenides.In this thesis,the author innovatively applied laser irradiation on TiSe₂ that partialy converts it to TiO₂.By combining its abundant optoelectronic and electronic properties,the optoelectronic behaviors and electrical transport properteis of various heterostructures based on TiO₂ are explored,which are expected to develop high-performance photodetectors and transistor devices in future.Firstly,the optoelectronic characteristics of the UV detector based on the in-plane heterostructure of TiSe₂/TiO₂ were systematically investigated based on understanding the mechanism of laser irradiation induced oxidation process.The results show that the device exhibits significant photocurrent response under deep ultraviolet（DUV）illumination at 254 nm,with the observation of an unconventional superlinear response behavior.A maximum responsivity of 182.8 A/W is achivieved under the applied illumination light power density of 87.3μW/cm² and the drain-source bias of 5 V.The detectivity also reaches a high value of 5.0×10¹¹ Jones.The device exhibits a fast dynamic response with a rise/fall time of 53/252 ms,respectively,while is relatively stable during measurements.Secondly,benifiting from the high dielectric constant of TiO₂,a MoS₂/TiO₂vertical heterojunction-based phototransistor was fabricated using the developed laser irradiation induced oxidation method.The device maintains a relatively high on/off ratio with a low value of subthreshold swing close to 60 mV/dec,approaching the thermal limit of the conventional metal oxide semiconductor field effect transistor.Photocurrent response behavior within visible wavelength region is observed,while the photocurrent generation mechanism switches from avalanche effect to photogating effect as the power density increases.