Z. F. Wang

Tuning the electronic structure of graphene nanoribbons through chemical edge modification : a theoretical study

We report combined first-principle and tight-binding (TB) calculations to simulate the effects of chemical edge modifications on structural and electronic properties. The C-C bond lengths and bond angles near the GNR edge have considerable changes when edge carbon atoms are bounded to different atoms. By introducing a phenomenological hopping parameter

Z-shaped graphene nanoribbon quantum dot device

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Chiral selective tunneling induced negative differential resistance in zigzag graphene nanoribbon: A theoretical study

for nearest-neighboring hopping to represent various chemical edge modifications, we investigated the electronic structural changes of nanoribbons with different widths based on the tight-binding scheme. Theoretical results show that addends can change the band structures of armchair GNRs and even result in observable metal-to-insulator transition.

Ballistic rectification in a Z-shaped graphene nanoribbon junction

Stimulated by recent advances in isolating graphene, we discovered that quantum dot can be trapped in Z-shaped graphene nanoribbon junciton. The topological structure of the junction can confine electronic states completely. By varying junction length, we can alter the spatial confinement and the number of discrete levels within the junction. In addition, quantum dot can be realized regardless of substrate induced static disorder or irregular edges of the junction. This device can be used to easily design quantum dot devices. This platform can also be used to design zero-dimensional functional nanoscale electronic devices using graphene ribbons.Stimulated by recent advances in isolating graphene, the authors discovered that a quantum dot can be trapped in a Z-shaped graphene nanoribbon junction. The topological structure of the junction can completely confine electronic states. By varying the junction length, the authors can alter the spatial confinement and the number of discrete levels within the junction. In addition, a quantum dot can be realized regardless of substrate induced static disorder or irregularities on the edges of the junction. The method can be used to easily design quantum dot devices. The authors also provide a platform to design zero-dimensional functional nanoscale electronic devices using graphene ribbons.

Electronic structure of bilayer graphene: A real-space Green's function study

The electronic and phase-coherent transport properties of a doped zigzag graphene nanoribbon are studied theoretically in this paper. The I-V curve of the device shows an interesting negative differential resistance (NDR) phenomenon. We found that the NDR is caused by the chiral tunneling of graphene, which is attributed to the symmetry of the eigenstates of individual subbands. This new physics finding is helpful for us to gain more insights about carrier transport in graphene nanoribbons and to design graphene-based nanoelectronic devices.

Modeling STM images in graphene using the effective-mass approximation

In this paper, we focus on a graphene heterojunction device: a Z-shaped graphene nanoribbon, which consists of two armchair leads and a zigzag junction. Based on the Landauer–Buttiker formula and the tight binding model, we found that the rectifying behavior can be achieved by applying an external gate voltage in the heterjunction region. We also found that the rectification effect is independent of junction width and length, it is an intrinsic property of the Z-junction graphene nanoribbon. This platform can be used to design and study functional graphene nanoscale devices.

A tunable quantum-dot device based on cross-bar graphene nanoribbon structures.

In this paper, a real-space analytical expression for the free Green’s function propagator of bilayer graphene is derived based on the effective-mass approximation. Green’s function displays highly spatial anisotropy with threefold rotational symmetry. The calculated local density of states LDOS of a perfect bilayer graphene produces the main features of the observed scanning tunneling microscopy STM images of graphite at low bias voltage. Some predicted features of the LDOS can be verified by STM measurements. In addition, we also calculate the LDOS of bilayer graphene with vacancies by using the multiple-scattering theory scatterings are localized around the vacancy of bilayer graphene. We observe that the interference patterns are determined mainly by the intrinsic properties of the propagator and the symmetry of the vacancies.