Study On The Electronic Transport Properties Of Optical Molecular Switch

With the rapid development of the computer, microelectronic devices based the traditional semiconductor materials silicon have reached their limit due to the limitation of the physical principle and the production process. The majority of researchers manufacturer molecular devices with different functions using nanometer scale molecules to solve this dilemma. With the development of advanced technology, many methods are applied to design and measure molecular devices with different functions, such as scanning tunneling microscopy(STM), mechanical controlled splitting, self-assembled monolayer and electromigration. It is found that molecular devices show a few of characters that ate similar to conventional microelectronic devices based silicon, for example, molecular rectification, negative differential resistance, memory function and molecular switch, etc.. Study on the molecular switch attracts more concern because it is the foundation of the future molecular circuit and information storage. Molecular switch is a kind of bistable quantum system with two different conduction characteristics under different trigger conditions. Common trigger conditions are STM, redox reaction, electric field regulation and light and so on. Among them, light stimulation is most likely to be used in the future, because it is easy to integration, address, fast switching speed, and the trigger condition is simple and convenient.In this paper, we investigated the electronic transport properties of a dithienylethene,hydantoin derivatives, and dicyanoethylene derivatives molecule sandwiched between two Au electrodes by applying non-equilibrium Green's function formalism(NEGF) combined with first-principles density functional theory(DFT). The main investigations are as follows:(1) It has been found from the dithienylethene molecular device that the current through the closed form is larger than that of the open form. The difference of the current is discussed in term of transmission spectra and molecular projected self-consistent Hamiltonian(MPSH) states.(2) According to the analysis of the I-V curve of hydantoin derivatives, we found that the current through the trans form is lager than that of the cis form. It clearly shows switching characteristics. In addition, we find that it will significantly improve the performance of the switch by adding fluorine atoms.(3) It can be found from the I-V curves of dicyanoethylene derivatives molecular devices that the current through the cis form is larger. The electronic transport properties for cis and trans forms are discussed in detail by the transmission spectra and molecular projected self-consistent Hamiltonian states. The observed negative differential resistance effect in the cis form is explained based on the transmission eigenstates of HOMO energy level.