11 research outputs found
Topological Line Defects around Graphene Nanopores for DNA Sequencing
Topological line defects in graphene represent an ideal way to produce highly
controlled structures with reduced dimensionality that can be used in
electronic devices. In this work we propose using extended line defects in
graphene to improve nucleobase selectivity in nanopore-based DNA sequencing
devices. We use a combination of QM/MM and non-equilibrium Green's functions
methods to investigate the conductance modulation, fully accounting for solvent
effects. By sampling over a large number of different orientations generated
from molecular dynamics simulations, we theoretically demonstrate that
distinguishing between the four nucleobases using line defects in a
graphene-based electronic device appears possible. The changes in conductance
are associated with transport across specific molecular states near the Fermi
level and their coupling to the pore. Through the application of a specifically
tuned gate voltage, such a device would be able to discriminate the four types
of nucleobases more reliably than that of graphene sensors without topological
line defects.Comment: 6 figures and 6 page
The quantum confined Stark effect in N-doped ZnO/ZnO/N-doped ZnO nanostructures for infrared and terahertz applications
The terahertz (THz) frequency range is very important in various practical applications, such as terahertz imaging, chemical sensing, biological sensing, high-speed telecommunications, security, and medical applications. Based on the density functional theory (DFT), this work presents electronic and optical properties of N-doped ZnO/ZnO/N-doped ZnO quantum well and quantum wire nanostructures. The density of states (DOS), the band structures, effective masses, and the band offsets of ZnO and N-doped ZnO were calculated as the input parameters for the subsequent modeling of the ZnO/N-doped ZnO heterojunctions. The results show that the energy gaps of the component materials are different, and the conduction and valence band offsets at the ZnO/N-doped ZnO heterojunction give type-II alignment. Furthermore, the optical characteristics of N-doped ZnO/ZnO/N-doped ZnO quantum well were studied by calculating the absorption coefficient from transitions between the confined states in the conduction band under the applied electric field (Stark effect). The results indicate that N-doped ZnO/ZnO/ N-doped ZnO quantum wells, quantum wires, and quantum cascade structures could offer the absorption spectrum tunable in the THz range by varying the electric field and the quantum system size. Therefore, our work indicates the possibility of using ZnO as a promising candidate for infrared and terahertz applications