Theoretical Study And Performance Modulation Of Multifunctional Organic Conjugated Molecular Devices

With the advancement of science and technology,the number of electronic devices on integrated circuits has gradually increased,and the requirements for device size have become higher and higher,which has reached the micro-nano scale.Traditional semiconductor silicon-based devices are facing great challenges.Molecular electronics is one of the methods that can increase the degree of integration.Many researchers look for various molecular devices with different functions on the nanometer scale to solve the size and efficacy problems of traditional devices.Among them,conjugated organic molecules are attracted much attenation due to their many types,easy preparation,low material cost,and?system conductive to electron delocalization.It is found that devices based on conjugated organic molecules have many good functions.Molecular devices of fused condensed-ring aromatic hydrocarbons and their derivatives are one of the research hotspots to date.Therefore,in this paper,the transport properties and regulation of1,4,5,8-naphthalenetetracarboxylic dianhydride?NTCDA?and 1,4,5,8-naphthalenetetra carbox diimide?NTCDI?based on the first-principles density functional theory?DFT?combined with nonequilibrium green's function?NEFG?were studied.This thesis mainly included the following parts:1,we mainly introduced the research background of molecular electronics and spintronics,the research status of organic conjugated molecular devices,several typical functions of molecular electronic devices,and briefly explained the basis of our research system and the significance of the research purpose.2,we mainly introduced the density functional theory and non-equilibrium Green's function method used in this paper,summarized the calculation methods of model design and performance parameters in the calculation of molecular device transport properties,and related calculation software used in the calculation process.package.3,we regulated the function of graphene electrode-NTCDA molecular devices through heteroatoms.In the calculation of the current-voltage curves before and after the regulation,it was found that after the carbon atoms at the junction were replaced by oxygen atoms,the rectification performance of the molecular device and the?double?spin filtering effect were improved.4,we mainly studied the spin transport performance of the graphene electrode-NTCDI molecular device,and found that its device has good spin filtering,double spin filtering,negative differential resistance,and rectification effects;then we rotated the central molecule to changes its relative position with the electrode to study the influence of the configuration on the switching performance of the molecular device.5,we connect the organic conjugated molecule NTCDI with another organic conjugated molecule benzene through acetylene to form an asymmetric molecular device.First,we study the charge transport properties and switching properties.By introducing functional groups amino?-NH₂?and Nitro?-NO₂?to regulate the performance of molecular devices.It was found that the electrical signal was significantly enhanced after the introduction of functional groups,and the switching ratio became larger.6,we made a brief summary and prospect of this research.