Electron Transport Properties Of Several Organic Molecules

In recent decades,with the continuous development of science and technology,electronic components based on silicon materials have become increasingly unable to meet the needs of people.The requirements for molecular devices are not limited to size,but also need to be further improved in performance.When reducing the size of a single electronic component,not only the production process complexity,production costs will increase significantly and the performance can not achieve a qualitative leap,but also restricted by quantum mechanics and thermodynamics,the development of silicon single molecular device is very difficult.But with the development of micro manipulation technology,micro assembly technology and micro observation technology,people can not only manipulate individual molecules of nanoscale molecular devices,making specific functions,but also on the molecular device structure observation and simulation.These molecular devices are considered to be the most suitable replacements for conventional electronic devices slowly approaching the scale limit.Therefore,people will pay more attention to the experiment and theory study.In this paper,based on the first principles method of density functional theory(DFT)and the non-equilibrium Green's function,we have studied the electronic transport properties of molecular devices.The research work includes the following three aspects:(1)The electronic transport properties of Sn-phthalocyanine(SnPc).The results show that,the spin-up/spin-down PDOS peak at 0.74 eV of SnPc will firstly move toward to the Fermi level and then be away from the Feimi level as the Sn atom is pulled out.A transform from spin-down filter to spin-up filter can be observed in parallel configuration due to spin flipping introduced by structural reorganization.While in anti-parallel configuration,the band structures of the two electrodes will play the dominant role in the electron properties of SnPc.The spin filter type conversion can be realized by pulling the Sn atom out of the SnPc or flipping the magnetic field of one electrode.(2)The effects of embedded magnetic atoms on the edge states and spin-dependent transport properties of zigzag 6,6,12-graphyne nanoribbon(6,6,12-Z GYNRs).The results show that spin splitting occurs when doping magnetic atoms in the natural "holes" of the 6,6,12-Z GYNRs.Particularly,the half-metallicity can be achievable by the magnetic doping of the Co atom,which originates from the reversion of magnetic moment of edge carbon atoms induced by the coupling between the edge and the impurity states.Furthermore,in such doped nanoribbons,a high spin-filtering effect in rather wide bias range is found,opening a huge possibility in spintronics device applications.(3)The effect of the coupling effect between the central molecule and the electrodes on the electronic transport properties of molecular devices is studied.The main observation angles between phenalenyl molecules and graphene nanoribbons are 0 °,30 ° and 60 °,which perform different electronic transport properties.The results show that the voltage and current characteristics of the molecular device are better with the increase of the deflection angle.