The Study On Electronic Transport Properties Of Heterogeneous Nanojuctions Composed By Ultra Small Diameter Carbon Nanotubes

Miniaturization of electronic devices is a significant feature in today’s scientific andtechnological development, which makes nanoelectronics become an intersecting disciplinecomposed by quantum chemistry, materials science and condensed matter physics. Dut to itsultra small and notable buckling effect, carbon nanotubes in small diameter have become ahot topic in theoretical and experimental studies. Currently, the smallest carbon nanotubewhich has been discovered so far in experiment is about0.3nm. Being Distinguished fromchirality, they are mainly armchair (2,2)carbon nanotube (CNT), zigzag (4,0)CNT, and spiral(3,1)CNT. The researching and studying on the electronic and transport properties ofultrasmall heterojunction composed by carbon nanotubes ench orther and their similardiameter semiconductor boron nitride nanotubes (BNNT) is a new issue of theoretical physics,especially to study the electronic properties and composition of new nano-heterojunction theelectronic transport properties, having a very important scientific significance, it will bepossible to promote the development of the most heterogeneous nano-thin nanoscale devices.In this paper, using first-principles calculation based on density functional theorycombining with Green’s function to electron transport calculation. Studying of the diameterof ultrafine carbon (2,2)nanotube,(4,0)carbon nanotube themselves or super latticestructure forming each other, and their corresponding superlattice diameter BN nanotubescomposed microstructure structure, electronic properties, transmission spectra, IVcharacteristics. By calculating and designing the new nanotube heterojunction and discussingtheir transport properties, laying the foundation for the kind of new nano-heterojunctionpotential nanodevice applications. Main results are:Formation energy of superlattice structure of (2,2)carbon nanotubes and boron nitridenanotubes is-3.072eV, indicating that this structure is stable and viable existence. Energy gapis1.37eV, existing among the energy gap in semiconductor materials. Coupling them betweentwo semi-infinite gold electrodes,to study the transport properties, results show that thiscomposite structure between Au electrode and nanotube is of strong coupling effect,effectively improveing the transport properties of nanotubes. By calculating respectively theIV characteristic curve of (2,2)CNT,(2,2)BNNT and (2,2)CNT/BNNT three electrodeconfiguration with gold, the results are similar to the large-diameter nanotubes and presentlinear characteristics which may be used in the quantum nano-diode circuit. Formation energyof superlattice structure of (4,0)carbon and boron nitride nanotubes is-5.0827eV, showingthat this structure is stable exist. Bandgap is0.738eV, therefore it is a narrow bandgap semiconductor material. Connecting them between two semi-infinite gold electrodes, thestrong coupling effect of the composite structure effectively improves their transportproperties. By calculating respectively the IV characteristic curve of (4,0)CNT,(4,0)BNNT,(4,0)CNT/BNNT three structures with gold electrodes, performing linear characteristics.Based on the above studies with chiral tube heterojunction, we also designed differentchiral nanotubes superlattice structure between (4,0)CNT or (4,0)BNNT tube and (2,2)CNTor (2,2)BNNT. Having Studied their electronic structure, the transmission spectra, and the IVcharacteristic curve. Discovering no matter what the heterojunction composite pipecombinated with the same or different nanotube chirality,IV characteristic curve after addingthe Au electrode showes that at the same bias the current is larger than any diametertube.indicating that the electronic transport properties of the ultrafine nanotubes is better thanlarge diameter nanotubes. This conclusion has important significance in the application ofnano-circuits.