Electro-catalytic Performance And FET Applications Of Few-layer MoS₂

Energy and environmental crises and the demand of higher performance material spurred the search for clean,efficient and high-performance materials.Geim and his study groups succeeded in obtaining single-layer Graphene in 2004.Due to the excellent chemical and physical properties of Graphene,it has received much concern.And it has a range of applications,such as microelectronics,energy storage and conversion.Thus,two-dimensional materials with excellent electrical and optical properties were widely explored.The structure of two-dimensional transition metal dichalcogenides are similar to Graphene with strong covalent bonding in layer and van der Waals bonding between layers.We can obtain few-layer or single-layer due to their layer structure.MoS2 is an indirect bandgap semiconductor with a band gap size of 1.3 eV.While the layers decrease,the band gap size increase.When the layers decrease to single-layer,MoS2 becomes a direct band gap semiconductor,and the gap size is 1.95 eV.MoS2 is widely used in field-effect transistors,optoelectronic devices and electrochemical catalytic and so on.When MoS2 using as a catalyst,the catalytic active sites are located in the edge of MoS2,while the in-plane of MoS2 is catalytic inert.Besides,MoS2 is a semiconductor,and its electrical conductivity is limited.Therefore,we need to improve the electrical conductivity and expose more catalytic active sites to improve the catalytic performance of MoS2.MoS2 is a promising material as an electric channel material in field-effect transistor,which is expected to replace silicon.But the mobility of MoS2 based back-gate field-effect transistors at room temperature is among 10-1 to 101 cm2 V-1s-1,thus there is an urgent need to improve its performance.Here we prepared metallic NbSe2 nanobelts through solid-phase reaction.Then using NbSe2 nanobelts as a supporting material,we synthesized MoS2/NbSe2 hybrid nanobelts with MoS2 nanosheets epitaxial growth on NbSe2 nanobelts'surface.The hybrid nanobelts have a core-shell structure.The hybrid structure reduced the stack of MoS2 nanosheets,exposing more catalytic active sites.And the metallic NbSe2 increases the electrical conductivity of hybrid nanobelts.Thus the hybrid nanobelts improve the efficiency of catalytic hydrogen produntion.We characterized the structure and composition of the sample through SEM,TEM,XRD,XPS and other methods.We also prepared MoS2 nanosheets by solid state reaction,and then the obtained MoS2 was tableted to a cylinder,then sintering again at high temperature in order to obtain larger size polycrystalline MoS2.This method is a very simple and efficient way to synthesis polycrystalline MoS2.We can obtain few-layer MoS2 by micro-mechanical exfoliation,using the few-layer MoS2 sample to fabricate back gate field-effect transistor and study the electrical performance at room and low temperature.We characterized the structure and composition of the sample through TEM,XRD,XPS;Raman,PL and other methods.