Physical Properties And Functional Devices Of Novel Two-dimensional Materials

The designing and exploring of new kinds of materials seem to be one of the anessential driving forces for the rapid development of modern technology.Especially,information devices based on novel materials have been playing a siginificant role in the applications of data storage and processing.Recently,two dimensional functional materials including graphene and transion metal dichalcogenides(TMDCs)are widely investigated for the advantages in their physical properties including tunable Fermi levels,amiable band gaps,and high carrier mobilities.They are thus believed to hold great promises in the implementations of next generation information devices including flexible electronics,smart dectors,and etc.In this dissertation,we systematically studied the physical properties of some layered compounds,such as few-layered GaTe,and designed nano devices with novel architecture based on them.Details of this study is list as follows:1.We synthesized single crystal GaTe with high-purity by self-flux method.GaTe field effect transistors(GaTe-FET),on which we performed electrical measurements,were prepared by nanofabrication technologies.To avoid the air-instability of GaTe-FET,we employed few-layered h-BN to encapsulate the thin GaTe flakes by a dry transfer method in a glove box.We hence fabricated h-BN/GaTe/h-BN van der Waals FETs,showing good stability in air and excellent electrical properties.2.We studied the electrical anisotropy of few-layered GaTe.Typical GaTe-FETs with 6 pairs of electrodes(300 angle between each two electrodes)were fabricated.By examine the electrical transport measurements,we found that few-layered GaTe exhibits strong electrical anisotropy,which can be further tuned by the gate voltage.3.Based on the above results,we fabricated a novel floating gate anisotropic memory with directional multi-level outputs.The floating gate memory was built in a full-vdW manner,employing few-layered graphene as the floating gate.This kind of device showed excellent memory properties such as largememory windows,high ON/OFF ratio,sensitive operating voltage response,as well as stable data storage capabilities4.In addition to the above studies of anisotropic 2D devices,we also investigated the possibility of 2D multi-ferroic devices for information applications.High quality CuInP2S6 and α-In2Se3 single crystals were also prepared by chemical vapor transport method,and their ferroelectric properties were characterized by PFM CuInP2S6 and a-In2Se3 field effect devices were fabricated and their electrical properties were characterized.Finally,we used van der Waals stacking technology to prepare MoS2/CuInP2S6/graphite heterostructure,and explored its potential application in a new two-dimensional ferroelectric resistive switching device.