Charge transport and mobility engineering in two-dimensional transition metal chalcogenide semiconductors

摘要

Two-dimensional (2D) van der Waals semiconductors represent the thinnest, airstable semiconducting materials known. Their unique optical, electronic andmechanical properties hold great potential for harnessing them as keycomponents in novel applications for electronics and optoelectronics. However,the charge transport behavior in 2D semiconductors is more susceptible toexternal surroundings (e.g. gaseous adsorbates from air and trapped charges insubstrates) and their electronic performance is generally lower thancorresponding bulk materials due to the fact that surface and bulk coincide. Inthis article, we review recent progress on the charge transport properties andcarrier mobility engineering of 2D transition metal chalcogenides, with aparticular focus on the markedly high dependence of carrier mobility onthickness. We unveil the origin of this unique thickness dependence andelaborate the devised strategies to master it for carrier mobilityoptimization. Specifically, physical and chemical methods towards theoptimization of the major factors influencing the extrinsic transport such aselectrode/semiconductor contacts, interfacial Coulomb impurities and atomicdefects are discussed. In particular, the use of \textit{ad-hoc} moleculesmakes it possible to engineer the interface with the dielectric and heal thevacancies in such materials. By casting fresh light onto the theoretical andexperimental works, we provide a guide for improving the electronic performanceof the 2D semiconductors, with the ultimate goal of achieving technologicallyviable atomically thin (opto)electronics.