Study Of Electronic Transport Properties In Moleculer Rectifier Based On Graphene

Nano-electronic devices attracted extensive attention in recent years.The molecular rectifier,which is the most basic functional molecular device,play an important role in future electronic logic circuits.Many methods have been proposed to improve the performance of rectifier devices both experimentally and theoretically.Graphene is considered as an ideal candidate for replacing silicon-based semiconductor materials for its excellent electrical properties.In this dissertation,I investigated the electronic transport properties of the molecular rectifying devices based on graphene nanoribbons using non-equilibrium Green's function formalism?NEGF?combined with first-principles density functional theory?DFT?.The doping,edge modification and trimming are proposed to improve the performance of devices.The conclusions obtained are as follow:?1?Calculating the I–V characteristics of the two co-doped 10-AGNR devices doped by boron and phosphorus atoms,we found the I–V curve is obvious asymmetry,which shows a strong rectification effect.If carbon atoms in the center of 10-AGNR device have been replaced by the boron and phosphorus atoms,the maximum reverse rectification ratio can reach 10⁷.The asymmetric doping of device can lead to a clear inverse rectification,which can be used to design a molecular rectifier with good performance.As the impurity atoms move to the edge from center position of 10-AGNR device,the observed rectification becomes to decrease.The results indicate that the asymmetric doping with different position of the impurity atom influences the electron transport of the device and plays an important role for the future design of graphene rectifiers.?2?We investigated the electronic transport of the 12-ZGNRs devices with modified edge by OH/NH₂,OH/NO₂ and OH/SO₂.For devices with modified edge by OH/NH₂,OH/NO₂,the currents display the obvious symmetry,which shows a weak rectification effect.For 12-ZGNRs device with modified edge by OH/SO₂,the maximum rectification ratio and reverse rectification ratio can reach 2076.33 and 1937.33 respectively.The results suggest that the edge modification of the OH/SO₂ has a positive effect on the electron transport of the device,and may be a potential application in designing future graphene rectifiers.?3?We studied the electron transport properties of AGNRs,in which 1,3,and 5 layers of carbon atoms are cut in the right half.When 1 or 3 layers of carbon atoms are cut in the device,the current-voltage curve shows a clear symmetry over the entire bias voltage range,which leads to a weaker rectification effect.When 5 layers of carbon atoms are cut in the device,the maximum rectification ratio and maximum reverse rectification ratio can reach259 and 218,respectively.The results show that the cutting has a certain influence on the electron transport of the graphene nanoribbon devices,and can provide direction for the design of future high-performance graphene rectifiers.