Research On Magnetoelectric Transport Characteristics Of 2D Materials Heterostructures

In the past fifty years,the semiconductor industry was booming.However,with the advent of the era of big data and artificial intelligence,the explosive growth of information and the consumer market have placed new demands on the data storage density and energy efficiency of semiconductor electronics and microelectronic devices.The significant quantum tunneling effect in small-sized devices and the high cost required for new device fabrication technologies make the further development of traditional semiconductor devices and microelectronic devices face huge challenges.In this context,the exploration of new materials and devices has become one of the potential solutions.The successful isolation of graphene in 2004 has led the academic community to pay considerable attention to two-dimensional(2D)nanomaterials.2D nanomaterial possesses almost all the functional properties of traditional materials,and researches based on 2D nanomaterials have extended to various fields.Due to their unique layered structure,2D materials exhibit novel physical and chemical properties that are different from traditional materials,such as the unconventional superconductivity in magic-angle graphene superlattices.On the other hand,the 2D material can form various heterojunctions with materials of any dimension without considering the problem of lattice adaptation based on the fact that each layer is connected by the van der Waals interactions,which is extremely important for the realization of multi-functional electronic,optoelectronic,spintronic devices.Among 2D materials,black phosphorus,transition-metal dichalcogenides(TMDs)and emerging magnetic 2D materials have also attracted wide attentions due to intriguing properties,such as ultra-high carrier mobility,strong spin-orbit coupling interaction,rich photoelectric characteristics and spin transport characteristics,which enrich the possibilities for fabrication of next-generation electronic nanodevices.Up to now,there have been a number of researches on the physical properties of these materials,however,the physical properties and mechanism of related heterostructures need further explorations.In this thesis,we mainly focus on the magnetoelectronic transport characteristics of black phosphorus(BP),SnS2,WTe2,Fe3GeTe2 and their heterojunctions.The main contents and results are as follows:(1)Research on magnetoelectric transport characteristics based on BP and BP-based heterojunction.The influence of channel length of BP and gate voltage on the electrical transport properties of BP-based transistors were studied.Multi-functionality and multi-state logic inverter were obtained in BP/SnSeS heterojunction by changing the BP channel length.Further,the spin orbit torque effect in BP/Permalloy heterojunction is investigated.Results revealed an out-of-plane spin-orbit torque due to the broken mirror symmetry in BP.(2)Research on magnetoelectric transport characteristics based on SnS2(WTe2)and SnS2(WTe2)-based heterojunction.Firstly,the SnS2 field effect transistor was employed as a carrier to explore the capability of the solid ionic liquid[EMP]+[TFSI]-.The capability of[EMP]+[TFSI]-was experimentally estimated to be?9.2 × 10-9 F/cm2.Next,the spin-orbit coupling effects of WTe2/in-plane magnetic anisotropy(WTe2/Permalloy)and WTe2/perpendicular magnetic anisotropy(WTe2/Ta 1 nm/TbCo 4 nm/Al 3nm)heterojunction systems were studied,respectively.Results demonstrated that there is a strong spin-orbit effect at the interface of both heterostructures.The spin-orbit torque efficiency in the WTe2/perpendicular magnetic anisotropy system increases as the thickness of WTe2 increases,and the maximum value reaches-0.14,which is higher than the values of heavy metals Pt.(3)Research on magnetoelectric transport characteristics based on Fe3GeTe2 and Fe3GeTe2/WTe2 heterojunction.The intrinsic perpendicular magnetic anisotropy of Fe3GeTe3 was verified by the abnormal Hall effect,and the Curie temperature Tc of 164.5 K was observed.By analyzing the anisotropic magnetoresistance effect,it is observed that the Fe3GeTe3 film undergoes a magnetic phase transition at around 120 K.The effects of current,magnetic field direction and temperature on the magnetoresistance effect of Fe3GeTe2/WTe2/h-BN heterojunction devices were studied.It is found that the Joule heat caused by the current dominates the variation of the device's magnetoresistance and that the magnetoresistance of this heterojunction is mainly determined by the perpendicular magnetoresistance of the Fe3GeTe3/WTe2 heterojunction.