Research on Two Dimensional Transition Metal Dicholcogenides Based Heterostructures’ Gas Sensing and Photoelectric Properties

Author:Niu Yue

Supervisor:wang rong guo jiao wei cheng


Degree Year:2018





Since the first experimental isolation of graphene in 2004,the interest on other layered 2D materials have kept growing.Moreover,the community working on 2D materials is rapidly moving from the fundamental study of these atomically thin materials towards integrating them with other advanced materials to create hybrid devices.Recently,a great deal of work on 2D materials based heterostructures has been done on different field like catalyst and energy.But for now,the heterostructures based on transition metal dichalcogenides are still very scarce for sensing application.In view of the above problems,this paper offers different methods for preparing transition metal dichalcogenides(TMDs)based heterostructures with different structures and morphology,and studies their gas sensing mechanism and photoelectric detective mechanism.We reported a facile way to produce reduced graphene oxided/MoS2(G/M)fibers for gas sensing.The gas sensing mechanism of the device was studied.And the sensing properties of G/M fibers were evaluated with NO2,NH3,humidity and other organics.And the gas sensitivities of G/M fiber devices with different proportion of graphene were also measured.The synergistic effect of rGO and MoS2in devices shows a higher sensitivity than individual components and ability to be manipulated by light illumination.The gas sensitivities of G/M fiber devices to NO2and NH3 are 75%and 200%,respectively.We reported a facile technique for the synthesis of G/M QDs for gas sensing.The as-prepared quantum dots show strong fluorescence.We studied the gas sensing mechanism for the quantum dots and assessed their sensing properties for NO2,NH3.To investigate the proper proportion of components,the gas sensitivities of G/MQDs with different proportion of GQDs were measured.At last,the photo-thermal performances of G/M QDs are studied to confirm the enhancement mechanism of light illumination.The theoretical LODs to NO2 and NH3 are calculated to be 41.4 ppb and 35.5 ppb,respectively.In this work we fabricated a vertical heterostructure by transferring the mechanical exfoliated MoS2 flakes on top of a LSMO thin film.The number of layers of TMDs flakes is determined by their optical properties.With the help of a homebuilt probe station equipped with carbon fiber microprobes,we investigated the electrical transport properties of the MoS2/LSMO heterostructures.The device presents a very large rectification ratio of103 and upon illumination displays photovoltaic effect with Voc up to 0.4 V.By staking a TiS3 ribbon onto p-type silicon,we fabricated a p-n junction based photodiode geometry.The optoelectronic performances of the fabricated TiS3devices are characterized in dark and upon illumination using a homemade scanning photocurrent system.Taking advantage of the high-speed optical communication and high responsivity of our devices,we demonstrated a single-pixel camera based on an ultrathin TiS3/Si photodetector.After testing the optoelectronic properties of TiS3/Si junctions for unpolarized light,we discussed the performances of these devices for polarized light detection,like polarized responsivity and detectivity.The heterostructure device demonstrates a broadband photodetecting range(from 405nm to 1050 nm)with high photo-responsivity(35 mA/W),but also shows a high sensitivity to polarized infrared illumination photodetection.The polarized contrast between b and a-axis direction of the TiS3 lattice is up to 350%and the anisotropy ratio for short circuit current reaches 0.64.