The Investigation Of Modified Phenyl Molecule's Transport Behavior And Its Application For ADC's Quantization Coding

With the development of traditional silicon semiconductor devices,the size of the devices becomes smaller and smaller,and the electronic law applied to describe the macro-scale devices will be replaced by quantum laws.Faced with the various restrictions,the traditional methods could not meet the needs of the development of miniaturized devices.Hence it is necessary to find new ways to describe the smaller devices.Compared to the traditional silicon semiconductor devices,the molecular devices have the advantage of miniaturization.During the past decades,tremendous achievements have been made.In theory research,first-principles non-equilibrium Green's method and condensate plastic model of multiple scattering matrix calculation method,etc.have been proposed.In this work,using first-principles method based on density functional theory combining with non-equilibrium Green's method,some devices model are built,and the corresponding transport properties,such as,the relationship between conductance and bias voltage,temperature or molecule length,are investigated.We introduce the development of the molecular devices and research significance of molecular devices,and introduce the density functional theory,non-equilibrium Green's method,and the software used in our calculation.Firstly,we investigate the conductance and transmission of three models,including the conductance and transmission spectrum influenced by electrode relative position,the conductance and transmission spectrum,influenced by angle between two electrodes in the counter-position device,as well as the conductance and transmission spectrum influenced by the section of electrode.Then,we analyze and discuss conduction mechanism in the different voltage and temperature.The results show that thermionic emission and Fowler-Nordheim tunneling exist in device based on BDT molecule.In addition,the linear relationship between conductance and temperature shows that the device based on BDT molecule could be used in the port of the quantization and coding in the analog-to-digital converter(ADC)device and the input-output(I-O)unit,and we discuss that the noise temperature is influenced by the linear temperature-draft.Lastly,we select thermionic emission as the main conduction mechanism,and investigate that conductance is influenced by the temperature,voltage and molecule length.Around Fermi surface,the linear temperature-draft is confirmed by continuous distribution of density of states.The breakdown voltage introduced is proved by the transmission spectrum under different voltage,which is consistent with the experiments.In order to explain experiment results,we put forward the special function determined by the effective section,the molecule length and the proportion of elements,and propose the mathematical formula.