A Study On Spin Transport Properties Of Graphene/h-BN Heterostructures

With the continuous improvement of the microelectronic devices' integration,the size of the silicon-based microelectronic device will reach the physical limit.As device size continues to decrease,the device fabrication process will become difficult due to the lithography and economic conditions.The device performance will also be changed due to wave-particle duality and thermodynamic restriction.Therefore,when the size of device reaches to nanometer level,the quantum effect must be considered.The emergence of nanoelectronics breaks through these limitations.Meanwhile,due to the introduction of quantum effect,many new features are found in the nano-electronic devices,such as negative differential resistance effect,nano-switches and so on.In addition,the development of nanoelectronics motivate people to pay attention to the application of electron spin properties in nanoelectronic devices,which produces nano-spintronic devices.By precisely manipulating the electron spin properties,the nano spintronic devices have the characteristics of faster response,lower power consumption and higher integration.Since the monolayer graphene was prepared experimentally in 2004,the study on graphene-based nano(spin)electronic devices has attracted a great attention.However,duo to the zero-bandgap of the graphene,it has many limitations in practical device applications.At the same time,it is noticed that hexagonal boron nitride(h-BN)has a similar lattice structure compared to the graphene.But the h-BN is a semiconductor with a broad bandgap.Therefore,the synthesis of graphene/h-BN is considered to be a good way to adjust the band structure.In 2010,Ci et al.firstly fabricated hybrid domains of graphene and h-BN in experiment.In 2014,Liu et al.fabricated the graphene/h-BN heterojunction by growing the h-BN on the edge of graphene.Subsequently,the study on the graphene/h-BN heterojunction has being thriving.The results show that the heterojunction has good conductivity and new electrical transport properties.However,still many problems on heterojunction has not been studied,such as the influence of interface type and metal doping on the transport properties.In our work,we systematically investigated the spin transport properties of the graphene/h-BN heterojunction by using the functional theory combined with on-equilibrium Green's function.For the emerging transport phenomena,we also discuss the physical mechanism and the application in the spintronic devices.The main contents and conclusions of the studies are as follows:1.Spin transport properties in graphene/h-BN heterojunction with different interface typesThe graphene/h-BN heterojunction mainly consists two geometries structures:zigzag interface and armchair interface.For the zigzag heterojunction,the theoretical studies show that the spin transport properties are better and the interface types of C-B and C-N are prepared in experiment.Based on this,we study the spin transport properties of the heterojunction of graphene/h-BN.The results show that the both C-B and C-N devices exhibit obvious spin filtering effect and the C-N device behaves the negative differential resistance properties.2.Spin transport properties of Fe-doped the heterojunction of graphene/h-BN.Because Fe has an important influence on the electronic structure and transport of graphene and h-BN,we simulated the regulation of spin transport by doping Fe at different sites of the heterojunctions.The study find that the device behaves spin-filtering,the negative differential resistance and rectifying effect.These results show that the heterojunction has great application in nano spin devices.At the time,these studies help us to design nano spin devices purposefully.