Quantum Transport Research On The Several New Two Dimension Molecular Devices

Accompanying the continuous miniaturization of electronic device, the conventionalsilicon-based electronic device will be in the face of the quantum effect challenge, likeelectronic diffraction, tunneling and interference. So the molecular electronics which is themolecular level electronics attract considerable attentions of theoretical and experimentalresearches. Molecular electronics whose purpose is using molecular clusters, supermolecules or single molecules instead of macroscopical electronic component likeconventional Silicon-based semiconductor devices to compose logical circuits orpowerfully computer can conquer the difficulty of the quantum effect and break thoughphysics and size limit. The main content of molecular electronics contain the molecularelectronic devices’ synthesis, realize certain logical circuits by assembling molecularelectronic devices and capability testing. The new generation molecular electronic devicesare believed to exceed CMOS technology and realize innovative device paradigm whichbase on advanced quantum transport mechanism like using spin instead of charge current.Spintronics research the quantum transport mechanisms of spin-polarization, spin currentand how to manipulate the spin degree in condensed matter physics. Comparing to theconventional electronics devices, the spintronics devices possess the following advantages:high sensitive, low power consumption, quick working speed and high density. By usingadvanced calculation technique, I make systemic investigations of some nanoscaleelectronic devices’ transport property like voltage-current curve, transmission spectrum,the molecular projected self-consistent Hamiltonian and energy band structure. The resultsshow that they are excellent nanoscale electronic devices with rectification effect, negativedifferential resistance phenomenon, spin diode effect and tunneling magneto resistance.My studies concentrate on the following several aspects: First, I utilize Boron-dopedgraphene nanoribbons to construct p-n junction. The right part of p-n junction is B-dopedat center of zigzag graphene nanoribbon and the left part of p-n junction is B-doped at theedge. I calculated the transport properties of this B-doped graphene nanoribbons p-njunction by nonequilibrium Green’s function method which is combining densityfunctional theory approach. The voltage-current curve, transmission spectrum, the molecular projected self-consistent Hamiltonian are showed to analyze B-doped graphenenanoribbons p-n junctions’ obvious rectification effect and novel negative differentialresistance phenomenon. I also find that the Boron-doping density’s modulation canmanipulate rectification ratio and induce novel negative differential resistancephenomenon. That is different from traditional p-n junction which is realized by introducedonor and acceptor impurity. It is considered that the mechanism of this transport propertyoriginate from this correlation between charges at center and edges and interactionbetween charge carriers and impurity. Second, experiment realizes the zinc-blend-typeCrTe thin films which grow on the ZnTe semiconductor by molecular-beam epitaxialgrowth method. So I make use of ZnTe/CrTe heterogenous junction to construct p-njunction and magnetic tunnel junction. The surfaces are chosen as (001) and (011) whichare realized in experiment. The zinc-blend-type CrTe is half-metallic magents and theZnTe is semiconductor. The results show that ZnTe/CrTe p-n junction possess outstandingspin diode effect and peculiar anisotropy. The rectification ratio of ZnTe(001)/CrTe(001)p-n junction is much higher than ZnTe(011)/CrTe(011) p-n junction. The spin diode effectis shown as minority spin current is completely inhibited and the majority spin current ofnegative voltage is obviously less than positive voltage’s. The magneto resistance ratio ofCrTe/ZnTe/CrTe magnetic tunnel junction is highly about4×109%which shows excellentapplication potential.