Electronic structures and optical properties of a SiC nanotube with vacancy defects

Based on first-principle calculations, the electronic structures and optical properties of a single-walled （7, 0） SiC nanotube （SiCNT） with a carbon vacancy defect or a silicon vacancy defect are investigated. In the three silicon atoms around the carbon vacancy, two atoms form a stable bond and the other is a dangling bond. A similar structure is found in the nanotube with a silicon vacancy. A carbon vacancy results in a defect level near the top of the valence band, while a silicon vacancy leads to the formation of three defect levels in the band gap of the nanotube. Transitions between defect levels and energy levels near the bottom of the conduction band have a close relationship with the formation of the novel dielectric peaks in the lower energy range of the dielectric function.

Working mechanism of a SiC nanotube NO_2 gas sensor

The working mechanism of sensors plays an important role in their simulation and design, which is the foundation of their applications. A model of a nanotube NO2 gas sensor system is established based on an （8, 0） silicon carbide nanotube （SiCNT） with a NO2 molecule adsorbed. The transport properties of the system are studied with a method combining density functional theory （DFT） with the non-equilibrium Green＇s function （NEGF）. The adsorbed gas molecule plays an important role in the transport properties of the gas sensor, which results in the formation of a transmission peak near the Fermi energy. More importantly, the adsorption leads to different voltage current characteristics of the sensor to that with no adsorption; the difference is large enough to detect the presence of NO2 gas.

Electronic transport properties of the armchair silicon carbide nanotube

The electronic transport properties of the armchair silicon carbide nanotube（SiCNT） are investigated by using the combined nonequilibrium Green＇s function method with density functional theory.In the equilibrium transmission spectrum of the nanotube,a transmission valley of about 2.12 eV is discovered around Fermi energy,which means that the nanotube is a wide band gap semiconductor and consistent with results of first principle calculations. More important,negative differential resistance is found in its current voltage characteristic.This phenomenon originates from the variation of density of states caused by applied bias voltage.These investigations are meaningful to modeling and simulation in silicon carbide nanotube electronic devices.

Negative differential resistance in an(8,0)carbon/boron nitride nanotube heterojunction

Using the method combined non-equilibrium Green’s function with density functional theory,the electronic transport properties of an（8,0） carbon/boron nitride nanotube heterojunction coupled to Au electrodes were investigated.In the current voltage characteristic of the heterojunction,negative differential resistance was found under positive and negative bias,which is the variation of the localization for corresponding molecular orbital caused by the applied bias voltage.These results are meaningful to modeling and simulating on related electronic devices.