Study On The Spin-Dependent Transport Properties Of Graphene-Based Devices

Based on the Moore’s law, the number of the transistors in the integrated circuit will be doubled every 18-24 months. As a law based on observation, its accuracy has been lasted over fifty years and it is said that it will also be right until the year 2020. As the size of the typical silicon-based semiconductors becoming smaller, we must take account of the principles of quantum mechanics. On the other hand, the techniques improved by experimentalists will be important support for finding materials with novel properties. So the study on theory is also necessary. To overcome the limits of the Moore’s law, there are two active fields:quantum computation and molecular electronics. The task of quantum computation is to compute, code and transport information using the principles of quantum mechanics. And the most annoying difficulty in quantum computation is the physical realization. However, the molecular electronics is focused on the typical logical devices to answer how the electron will move in molecules. Then spintronics has made the spin degree of electron to be considered in single molecule. So this is the molecular spintronics.Reed et al. measured the Ⅰ-Ⅴ curve of a single molecule for the first time in the year 1997. Then the molecular electronics became one of the promising fields for fabricating molecular computer. In 2004 Novoselov et al. firstly found the existence of graphene in experiment and it behave high quantity for conductance and novel electrical properties. There have been a majority of study on the graphene in the next years. In 2006, Son et al. observed that the zigzag-edged graphene nanoribbons behave spin polarized behaviors in the electric filed. This opened an field for the realization of spin filtering devices based on graphene. As two-dimensional GNRs can be easily designed as functionalized nanodevices by cutting into various shapes, changing its geometric configurations, chemical doping, introducing vacancy and so on, we can see the promise for applications in spin related electronic devices. ZGNRs can be used as electrodes to act as spin generation materials. The magnetic configurations of ZGNRs electrodes can be designed as parallel (P) or antiparallel (AP) by changing the relative direction of the local magnetic field applied on the electrodes. On the other hand, graphitic carbon nitrides (g-C3N4) has attracted considerable attention because of its promising application in electronic devices, since it has been synthesized by a variety of methods. G-C3N4 is regarded as the most stable allotrope in ambient conditions, and the electronic structures differing significantly from those of graphene.In our work, using nonequilibrium Green’s functions in combination with the density functional theory, we investigate the electronic transport properties of two nanostructe devices based on graphitic carbon nitrides bridging two zigzag graphene nanoribbons. We will also consider the hererojunctions based on zigzag-edged graphene nanoribbons and g-C3N4 nanoribbons. It is reported that our constructed devices behave spin negative differential resistance properties, high spin filtering and high rectification ratio. The magnetic properties indicate potential application in molecular spintronics.