Preparation And Properties Of Molybdenum Diselenide And Its Microelectronic Devices

In recent years,two-dimensional（2D）materials have attracted a lot of attention due to their unique physical structures and chemical properties.Molybdenum diselenide（MoSe₂）,a bandgap-tunable two-dimensional material with a special crystal structure,exhibits different electrical and optical properties and has potential as a candidate material for microelectronic devices.In this paper,we used MoSe₂ was prepared by hydrothermal method,and the morphology and structure of the material were adjusted by process parameters;and the resistive memory（RRAM）with low power consumption,high switching ratio and high cycle times was prepared by using it as a resistive layer,and the switching ratio and tolerance of the device were further improved by coating with polymethyl methacrylate（PMMA）.Finally,MoSe₂ was used as the photosensitive layer of the photodetector,and its photosensitive characteristics were investigated under different test conditions.The following research results have been achieved:（1）MoSe₂ was successfully synthesized by the hydrothermal method with Na₂Mo O₄and Se powder as raw materials,and N₂H₄·H₂O and H₂O as solvents.The MoSe₂ morphology and structure were regulated by changing the ratio of N₂H₄·H₂O to H₂O and the reaction time.The final flower spherical structure,which could be assembled by nanosheets,was obtained with a regular morphology and a particle size of about 200 nm.The optimal process was a 1:1 ratio of water to hydrazine hydrate and a reaction time of 48 h.（2）The MoSe₂ dispersions were prepared into resistance-switching layer films by adopting the suction filtration method.The Ag/MoSe₂/Cu and Ag/MoSe₂-PMMA/Cu structured RRAMs were constructed with glass sheets as substrates,respectively,and their resistance characteristics were studied.The current-voltage（I-V）curve of the Ag/MoSe₂/Cu RRAM demonstrated that the device has the bipolar resistive switching phenomenon,which featuring good endurance with the operating voltage of about 0.74 V,the switching ratio of about 1.3×10~2,and the cycle number of about 10~3.Other than that,by coating with PMMA,the on-off ratio increased to about 2×10~2;and the cycle number increased to about 1.6×10~3,which demonstrated a 1.5 and 1.6 times enhancement,respectively.Furthermore,the flexible performance of the device was investigated using polyethylene terephthalate（PET）as the substrate.The device without PMMA lost its resistive switching characteristics after bending 10~3 times,while that with PMMA still maintained its resistive switching characteristics.According to the I-V curves fitting analysis of MoSe₂ and MoSe₂-PMMA RRAM,the resistance mechanism is mainly led by the SCLC mechanism to transport the charge,forming localized conductive filaments,and realizing multi-level storage characteristics through the control limiting current(I_cc)and cut-off voltage(V_stop).（3）A prototype MoSe₂ photodetector device was prepared,and its photoelectric properties were systematically investigated.The results show that the MoSe₂ photodetectors possess good photoelectrical properties under the irradiation of different laser wavelengths,with the maximum responsivity of 7.5×10^-5A/W and the corresponding optical detectivity of 1×10~6 cm·Hz^1/2/W at the laser intensity of 0.5 m W.Besides,the responsivity and detectivity increase with the increase of laser power.In addition,the detector response is fast,when a rising response time is 68 ms and a falling response time is 57 ms.