Study On The Electronic Transport Properties Of Graphene Nanoribbon Devices

With the rapid development of modern science and technology,the demand for integrated circuits and electronic devices tends to be smaller,colder and faster.Therefore,the development of traditional silicon-based devices has entered a bottleneck stage,molecular electronics has gradually emerged and has attracted a lot of interest from researchers.In recent years,with the appearance of high-tech such as molecular assembly structure technology,molecular material preparation technology,and molecular design technology has made it possible to manipulate atoms at the molecular scale.By combining single molecules with metal electrodes,scientists have produced functional molecular devices with diverse properties,including molecular rectification effects,negative differential resistance?NDR?,and molecular switching.In this paper,a first-principles calculation method combining density functional theory?DFT?and non-equilibrium Green's function?NEGF?is used,to study the charge transport properties of two typical central molecules based on graphene nanoribbons?GNRs?and graphene-like C₂N-h2D nanoribbons electrodes,and a series of interesting results were found.The specific research content has the following three points:?1?A dipyrimidinyl-diphenyl molecular device based on an armchair-edged graphene nanoribbon?aGNRs?electrode was constructed.We investigated the effects of asymmetric doping of electrodes on the electronic transport properties of molecular devices.The results show that,the diblock co-oligomer molecular device can have rectification and NDR characteristics by doping nitrogen atoms,and the doping position has a great influence on the electronic transport properties of the molecular device.Doping at the edge of the right electrode can cause rectification effect.Doping at the center of the right electrode can not only improve the conductivity of the molecule,but also produce a significant NDR effect and a more significant rectification effect.The rectification ratio is up to 42.9 at a voltage of 1.5 V.?2?We studied the electronic transport properties of dipyrimidinyl-diphenyl molecules embedded in a carbon atomic chain sandwiched between zigzag-edged graphene nanoribbon?zGNRs?and different edge geometries C₂N-h2D electrodes.Compared with the graphene electrodes,the C₂N-h2D electrode can cause rectifying and NDR effects.For C₂N-h2D with zigzag-edged,there was a more remarkable NDR phenomena,whereas for armchair-edged C₂N-h2D,which can give rise to much better rectifying behaviors.The rectification ratio is up to 15.6 at a bias voltage of 0.4 V,which is almost four times of the zigzag-edged C₂N-h2D nanoribbon.?3?The effect of the edge shape of the GNRs electrode on the switching characteristics of the photo-switching molecule butadienimine was investigated.The results show that a higher current switching ratio can be obtained for the molecular junctions with zGNRs,and the switching ratio can up to 8.7,which is greater than the switching ratio of the butadieneimine molecule which is connected to the gold electrode.When the electrode is an aGNRs electrode,the switching ratio is controlled by the band gap,and the smaller the band gap,the larger the switching ratio.These results can be potentially useful for the design of logic and memory devices.