•Z-shaped MoS2 nanoribbon atomic-perfect-interface planar junctions are constructed.•The electronic transport mechanism of Z-shaped devices is theoretically clarified.•Bipolar transistors and Schottky barrier diodes with good performance.•Different scaling rules of on/off ratio as a function of the length and width of the channel.Based on MoS2 nanoribbons, metal-semiconductor-metal planar junction devices were constructed. The electronic and transport properties of the devices were studied by using density function theory (DFT) and nonequilibrium Green's functions (NEGF). It is found that a band gap about 0.4 eV occurs in the planar junction. The electron and hole transmissions of the devices are mainly contributed by the Mo atomic orbitals. The electron transport channel is located at the edge of armchair MoS2 nanoribbon, while the hole transport channel is delocalized in the channel region. The I-V curve of the two-probe device shows typical transport behavior of Schottky barrier, and the threshold voltage is of about 0.2 V. The field effect transistors (FET) based on the planar junction turn out to be good bipolar transistors, the maximum current on/off ratio can reach up to 1 × 104, and the subthreshold swing is 243 mV/dec. It is found that the off-state current is dependent on the length and width of the channel, while the on-state current is almost unaffected. The switching performance of the FET is improved with increasing the length of the channel, and shows oscillation behavior with the change of the channel width.

Using the nonequilibrium Green’s function method combined with spin-polarized density functional theory, we investigate the spin-resolved electronic transport properties of devices made of poly-(terphenylene-butadiynylene) (PTB) between two symmetric ferromagnetic zigzag graphene nanoribbon (ZGNR) electrodes. The bipolar spin filtering effect, rectifying behavior, and negative differential resistance have been found. More interestingly, an on/off ratio in the order of 107 is also predicted by changing the angle between the PTB and ZGNR electrode planes. Further analyses show that the matching of the electronic wave functions among both electrodes and PTB plays a key role in the multi-functional PTB based device. And the coupling between the alkyne triple bond and the phenyl rings of PTB is critical to the value of the spin-resolved current and the on/off ratio. These phenomena suggest that the proposed PTB based devices have potential utilization in molecular spin diodes and molecular switches.

•The spin-dependent electronic transport properties of zigzag silicene nanoribbons.•Effects of the asymmetric edge hydrogenation on spin-dependent transport.•Bipolar spin-filtering, rectifying and giant magnetoresistance effects can be observed.Using the nonequilibrium Green's function method and the spin-polarized density functional theory, the spin-dependent electronic transport properties of zigzag silicene nanoribbons (ZSiNRs) with asymmetric edge hydrogenation have been studied. The results show that there exists nearly 100% bipolar spin-filtering behavior in the ZSiNR-based devices with antiparallel spin configuration. Moreover, rectifying behavior and giant magnetoresistance are found in the devices. Our calculation suggests ZSiNRs with asymmetric edge hydrogenation as a promising candidate material for spintronics.

The fluorination of dithiophene-tetrathiafulvalent (DT-TTF) was investigated by using the density functional theory combined with nonequilibrium Green's function method. It is demonstrated that fluorination can modify the electronic transport properties of DT-TTF. Negative differential resistance can be observed within a certain bias voltage range in 4FDT-TTF.Highlights► Fluorination effects on the electronic transport in TTF molecular junction. ► F-substitution can modify the electronic transport properties of DT-TTF. ► NDR can be observed within a certain bias voltage range in 4FDT-TTF.

By using nonequilibrium Green’s function method and first-principles calculations, the electronic transport properties of doped C60 molecular devices were investigated. It is revealed that the C60 molecular devices show the metal behavior due to the interaction between the C60 molecule and the metal electrode. The current-voltage curve displays a linear behavior at low bias, and the currents have the relation of M1>M3>M4>M2 when the bias voltage is lower than 0.6 V. Electronic transport properties are affected greatly by the doped atoms. Negative differential resistance is found in a certain bias range for C60 and C58BN molecular devices, but cannot be observed in C59B and C59N molecular devices. These unconventional effects can be used to design novel nanoelectronic devices.

In order to simulate the stress of turbine rotor in aeroengine, based on the ANSYS, the simplification model of the turbine rotor was built up. By applying the simplification model, the contact stress of turbine rotor was computed. The maximum contact stress appears at the chamfer below the flank, which agrees with experiment result. At the same time, the contact stress changing with the flank angle and friction coefficient was calculated, The results show that the contact stress in the flank increases slowly with the increase of flank angle; with the friction coefficient increasing, the contact stress in flank length decreases; the contact stress will not change when the friction coefficient is over 0.25.

By using nonequilibrium Green's functions in combination with the density–function theory, we investigate electronic transport properties of molecular devices with pristine and partial hydrogenation. The calculated results show that the electronic transport properties of molecular devices can be modulated by partial hydrogenation. Interestingly, our results exhibit negative differential resistance behavior in the case of the imbalance H-adsorption in C60 molecular devices under low bias. However, negative differential resistance behavior cannot be observed in the case of the balance H-adsorption. A mechanism is proposed for the hydrogenation and negative differential resistance behavior.Highlights► The transport properties can be modulated by partial hydrogenation. ► The transport properties of C60 molecular devices depend on the absorptions site. ► At low biases, the imbalance H-adsorption can enhance the electron transport. ► At low biases, the balance H-adsorption can suppress the electron transport. ► Negative differential resistance behavior can be observed in the case of pristine.

By using the first-principle calculations and nonequilibrium Green functions method, the electronic transport properties of molecular devices constructed by C82, C80BN and C80N2 were studied. The results show that the electronic transport properties of molecular devices are affected by doped atoms. Negative differential resistance (NDR) behavior can be observed in certain bias regions for C82 and C80BN molecular devices but cannot be observed for C80N2 molecular device. A mechanism for the negative differential resistance behavior was suggested.

The fluorination of dithiophene-tetrathiafulvalent (DT-TTF) was investigated by using the density functional theory combined with nonequilibrium Green's function method. It is demonstrated that fluorination can modify the electronic transport properties of DT-TTF. Negative differential resistance can be observed within a certain bias voltage range in 4FDT-TTF.Highlights► Fluorination effects on the electronic transport in TTF molecular junction. ► F-substitution can modify the electronic transport properties of DT-TTF. ► NDR can be observed within a certain bias voltage range in 4FDT-TTF.

•The phenomenon of single-electron field emission in a transistor setting using self-assembled gold nanoparticles was investigated.•The transfer characteristics can be well explained by the model that is a combination of Coulomb blockage and field emission.•This transport mechanism is novel and may be used in many applications in field emission devices.Coulomb blockade mediated field-emission current was observed in single-electron tunneling devices based on self-assembled gold nanoparticles at 300 K. According to Raichev's theoretical model, by fixing a proper geometric distribution of source, island and drain, the transfer characteristics can be well explained through a combination of Coulomb blockade and field emission. Coulomb blockade and field emission alternately happen in our self-assembled devices. The Coulomb island size derived from the experimental data is in good agreement with the average size of the gold nanoparticles used in the device. The integrated tunneling can be adjusted via a gate electrode.