Study On Transport Properties Of Carbon And Boron Based Low Dimensional Nanostructures

With the progress of science and technology and the development of nanotechnology and nanomaterials,the integration of electronic devices is getting higher and higher,and the size of devices is decreasing gradually,which also brings some problems such as quatum effect interference.In order to deal with these problems,the research of electronic devices based on low-nanometer materials has become the main development direction.Based on the first principles and non-equilibrium Green’s function and density functional theory,the electron transport properties of low-dimensional carbon-based and boron-based nanomaterials are studied.First of all,taking monolayer fluorinated diamond as the research object,one-dimensional fluorinated diamond nanoribbon is obtained by cutting,optimization and calculation.After the calculation of nanoribbons with different widths,it can be found that the spin-dependent electrothermal effect,namely Spin Seebeck effect,is accompanied by parity.When the width atom number is even,both ends of the fluorinated diamond bipolar structure have a temperature gradient,which makes the structure spontaneously generates spin polarization current.The spin up current is positive,the spin down current is negative,and the current value increases with increasing temperature.In order to explore the cause of the Spin Seebeck effect,the Fermi-Dirac distribution is drawn in this paper.Secondly,taking the cyclopropyl lithium derivative molecule[{μ-c-CSi Me₃ZC₂H₄}Li]₄ as the research object,the transition metal chromium was doped at different positions of the molecular structure,and the electron transport properties under different doping states were calculated.It is found that the molecular structure doped with chromium on the left and right sides can realize the regulation of spin polarization from negative to positive by changing the grid voltage in the case of building three different grid structures,and the regulation ability of different grids on the structure is also different.Meanwhile,this article constructs bicyclopropyl lithium derivative molecules and optimizes them to maintain stability.With the carbon chain coupling double molecular structure,set up double probe system,calculates the I-V characteristic curve,found that the molecular structure of double has significant negative differential resistance phenomenon.Through further analysis,it is found that the molecular state weakening under bias modulation leads to Negative Differential Resistance（NDR）.Finally,taking borazine derived nanowires as the research object,three kinds of nanowires with different lengths are constructed and optimized to ensure their stability.Then,the gold electrodes were coupled at appropriate positions at both ends of the nanowires,and the I-V characteristic curves were calculated respectively.Significant negative differential resistance phenomena were found in both of them.And as the length of the nanowires increases,the current at the same voltage decreases.By further calculating the local density of states and intrinsic transmission channels,it was investigated that the main reason for the occurrence of negative differential resistance phenomenon is the weakening of molecular states under bias modulation.The three structures studied in this paper are all low-dimensional nanomaterials.The unique electron transport properties of the three structures provide development directions for the design and research of electronic devices in the future.