Theoretical Calculation Of Electronic Transport Properties Of Several Single Layer Nanomaterials

The early 20th century was the golden age of electronic science,and the advent of electronic diodes was called the beginning of electronic technology.The emergence of integrated circuits has opened the way of miniaturization of electronic devices.With the rapid development of electronic technology,the requirements for the integration of electronic devices are getting higher and higher,and traditional electronic devices have been unable to meet people's development requirements.Therefore,the research of nanometer and molecular devices is of great significance.Low-dimensional nanomaterials,such as graphene,single-molecule,heterojunctions,exhibit electronic properties similar to those of microscale electronic devices,such as negative differential resistance characteristics,current limiting characteristics,etc.In this dissertation,the non-equilibrium Green's function and density functional theory are used to explore the electronic transport properties of several types of single-layered nanomaterials,including heterojunctions,edge modified or doped nanoribbon structures.The main job consists of the following parts:1.We have explored the electron transport properties of phosphorene-like MX?M=Ge/Sn,X=S/Se?nanostructures.The Ge S and GeSe nanoribbons display the very similar electronic transport properties.Their current-voltage?I–V?curves exhibit the interesting negative differential resistive?NDR?effect and are insensitive to their ribbon widths.The currents propagate through the GeS and GeSe nanoribbons mainly along the metal-termination.Most SnS nanoribbons could present the current-limited effect.Under the low bias,the SnSe nanoribbons also show a negative differential resistive effect only.2.We investigate the electronic structures and transport properties of zigzag blue phosphorene nanoribbons?ZBPNRs?,whose both edges are passivated with different groups?i.e.,-H,-O,and-OH?.These groups can obviously tune the electronic structures and transport properties.ZBPNRs-H presents a semiconductor property,and their indirect band gap changes little with the ribbon width increasing.ZBPNRs-O displays the metallic characters and its current-voltage curve exhibits a negative differential resistance effect and is independent of its ribbon widths.ZBPNRs-OH displays a similar semiconductor property with a direct band gap.3.We study the electronic transport properties of zigzag MoS₂ nanoribbons?ZMoS₂NRs?.The current-voltage curves of ZMoS₂NRs show the negative differential resistive effect,and are independent of nanoribbon width.The current flowing through the nanoribbon is mainly along the Mo-edge,with two different local current channels?Mo?Mo hop current and S?Mo?S bond current?.The current will be suppressed when introducing a Mo vacancy-defect at the Mo-edge under the low biases.While,under the high biases,the current through the defected Z-MoS₂NRs will increase a little,due to the other S-edge channel is opened.4.We study the electronic transport properties of several types of zigzag MoS₂–WS₂ lateral heterojunctions.The MoS₂–WS₂ lateral heterojunctions show an interesting negative differential resistive effect,due to owning very similar band structures to that of the pristine Mo S₂ and WS₂ nanoribbons.The electrons always propagate through the heterojunctions along the metal-terminations.The results demonstrate that the proposed transition-metal dichalcogenides heterojunctions could become the candidates of negative differential resistive devices,and have the potential applications in nanoelectronics.