Electronic Transport Properties Of Molecular Devices Based On Pyridine And Siloxane Rings

Molecular devices have attracted much attention in nanoelectronics due to the advantages of their unique size and good performances.They are the basic elements of integrated circuits and have wide range of applications,including logic and storage devices,smart materials,sensors,molecular motors,molecular-scale transistors,etc.Molecular devices have become the focus of key development in various advanced countries in the world.The electronic transport properties of molecular devices and the effects of various factors on transport properties play a key role in the applications of devices.Therefore,the analysis of the electronic transport mechanism,the exploration of new molecules,and the influence of the electrode and other components on the transport properties are always needing be solved.Pyridine molecules are very popular in highly conductive molecular devices due to their characteristic pyridine rings.In this paper,firstly first-principles based on density functional theory and non-equilibrium Green's function method are used to explore the effect of different electrode materials(three-dimensional metal electrodes:gold,silver,copper;two-dimensional graphene electrodes;one-dimensional narrow zigzag graphene nanoribbon electrodes with different widths)on the electronic transport properties of basic pyridine molecule devices.The results show that the basic pyridine molecular device constructed with a 4-atomic wide zigzag graphene nanoribbon electrode has the best electronic transport performance.It is mainly manifested in that the device has the strongest electron transmission at the Fermi level,which is determined by its delocalized electronic states;only this device exhibits negative differential resistance effect with great application value,due to the weakened influence of the initial dominant molecular orbital on the electron transport;this device possesses the strongest coupling between the pyridine molecule and this electrode.Based on the one-dimensional narrow zigzag graphene nanoribbon electrodes with the best performance,this article then analyzes the electronic transport properties of two types of pyridine molecular(conjugated and saturated chain bridged)devices.The results show that these two types of molecular devices have been demonstrated excellent non-equilibrium electronic transport behavior by virtue of their unique molecules and electrodes.Conjugated pyridine molecular devices have strong currents,derived from delocalized electronic states,bimodal to unimodal transmission peak evolution because of the replacement of the dominant transport orbital,and strong negative differential resistance effect due to the weakening influence of the initial dominant orbital on the electron transport;the device connected by saturated bridges shows multiple negative differential resistance effects which is caused by the combination of the localized electronic states and higher velocities away from the Fermi level and rectification behavior due to the comprehensive effect of apparently asymmetric electronic states of the dominant transport orbital and its completely different response to positive and negative biases.These physical behaviors indicate that they have a wide range of applications in the development of high-speed logic devices,and show the bright application prospects of narrow zigzag graphene nanoribbon electrodes and pyridine molecules in molecular electronics.Molecular insulators are just as important as molecular conductors.They can prevent electronic crosstalk between conductors in a molecular array,and play a key role in the development of single-molecule electronic components.Inspired by the pyridine ring,we changed the normality of linear molecular insulators and have studied the electronic transport properties of the devices based on siloxane molecular rings in comparison with the devices with alkane rings.Results show that molecular devices with siloxane rings has stronger electron transport inhibition and faster size-dependent electron decay rate,which is caused by its highly localized electronic states,basically depending on the unique electronic coupling mode of siloxane molecular rings.Such mode is determined by the strong polarity of the Si-O bond,which results in the localization of the charge,making the siloxane ring's weak electronic coupling and suppressing the electron transport.The transport decay of the devices with alkane molecular rings is due to the increased localization of electronic states during the charge transfer process,that is,the enhancement of the potential barrier at the molecular-electrode interface.In addition,the weakened electronic transport of the molecular ring device results from the increased fluctuation degree of the overall structure of the molecular ring.These studies demonstrate the superiority of siloxane molecular rings as molecular insulators.This paper explores the electron transport properties of cyclic molecular devices from the perspective of molecular type,size,and electrodes,and predicts a number of different functional molecular devices.The research results in this article is helpful for understanding the transport properties of molecular devices and provide theoretical support for the design and application of functional molecular devices.They are of great significance to promote the application of circular molecules in integrated circuits.