Xin-Jun Wang

Ballistic thermal conductance in graphene nanoribbon with double-cavity structure

We investigate phonon transport and thermal conductance in a Graphene Nanoribbon modulated with a double-cavity quantum structure at low temperatures. Two methods are compared: the force-constant and elastic wave continuum models. Calculations show that both the models show the similar thermal conductance property at low temperatures despite the excited theory of the discrete phonon modes in quantum structure being not the same. However, in the higher temperature region, the thermal conductance in the force-constant model is bigger than that in the elastic wave continuum model. The difference originates from the inequable cutoff frequencies of the phonon modes. A brief analysis of these results is given.

Plasmon resonances in a stacked pair of graphene ribbon arrays with a lateral displacement

We find that a stacked pair of graphene ribbon arrays with a lateral displacement can excite plasmon waveguide mode in the gap between ribbons, as well as surface plasmon mode on graphene ribbon surface. When the resonance wavelengthes of plasmon waveguide mode and surface plasmon mode are close to each other, there is a strong electromagnetic interaction between the two modes, and then they contribute together to transmission dip. The plasmon waveguide mode resonance can be manipulated by the lateral displacement and longitudinal interval between arrays due to their influence on the manner and strength of electromagnetic coupling between two arrays. The findings expand our understanding of electromagnetic resonances in graphene-ribbon array structure and may affect further engineering of nanoplasmonic devices and metamaterials.

Heat transport in multilayer abrupt graphene junctions modulated with convexity-shaped quantum structure

By using the force-constant and elastic wave continuum models, we investigate the ballistic phonon transport and thermal conductance in multilayer zigzag graphene nanoribbon junctions modulated with convexity-shaped quantum structures at low temperatures. The results show that the convexity-shaped (T-shaped or H-shaped) quantum structure can enhance thermal conductance at very low temperatures. The enhancement originates from the increased attenuation length of the evanescent modes in convexity-shaped quantum structures. A brief analysis of these results is given.

Synthesis of high-quality carbon nanotube arrays without the assistance of water

Long and high-quality carbon nanotube (CNT) arrays have been synthesized through a chemical vapor deposition process. The Fe/Al2O3 on silicon was used as the catalyst, ethylene as the carbon source, and a gasmixture of Ar and H2 gases as the carrying gas. It is found for the first time that the high-quality and superlong carbon nanotube array can be improved by varying the content of hydrogen and carbon source.

Plasmon resonances in a periodic square coaxial hole array in a graphene sheet

We present a computational study of the plasmon resonances in a periodic square coaxial hole array in a graphene sheet, which consists of a square hole array and a square strip array. According to charge oscillation picture, we find that a new plasmon mode, which locates on the edges of square hole along the polarization direction of incident light, emerges in our proposed structure. Two hybridized plasmon resonance modes (i.e., symmetric and asymmetric plasmon resonance modes) are formed due to two different manners of coupling between the new plasmon mode of square hole and the plasmon mode of square strip. The two plasmon resonance modes can be tuned over a wide wavelength range by a small change in the chemical potential of graphene. Furthermore, the two plasmon resonances can also be controlled by changing Lx and Ly (which are the strip offsets from the hole center perpendicular and parallel to the polarization direction of incident light, respectively), originating from the change in the strength of electromagnetic coupling between square hole and square strip. Our study gives an insight into the physical mechanism of plasmon resonances in square graphene coaxial hole array, and our findings will be useful for designing graphene-based plasmonic devices and metamaterials.

Light transmission through a one-dimensional metallic grating covered by a reduced cytochrome c molecule layer

We investigate the transmission characteristics of a one-dimensional metallic grating covered by a reduced cytochrome (Cyt) c molecule layer by using the finite-difference time-domain (FDTD) method. It is found that the introduction of reduced Cyt c molecule layer leads to a transmission dip due to the plasmon resonance energy transfer (PRET) from metallic grating to Cyt c molecules. The transmission dip depth can be controlled by the period of metallic grating, the width and length of slit, and the Cyt c molecule layer number, while the transmission dip wavelength is unchanged with these parameters. The findings expand our understanding of the PRET phenomenon and have potential applications in molecule identification and detection.

Plasmon Resonances in a Stacked Pair of Periodic Graphene Hole Arrays

In this paper, we investigate the plasmon resonances in a stacked pair of periodic graphene hole arrays by using charge oscillation picture. It is found that the plasmon resonances can be controlled by changing the longitudinal interval G between two arrays, and the lateral displacements Lx and Ly, which are parallel and perpendicular to the polarization direction of the incident light, respectively. The plasmon resonance can be tuned over a wide wavelength range by a small change of G due to its influence on the strength of electromagnetic coupling between two arrays. The lateral displacement Lx causes new plasmon resonance modes, originating from the appearance of new electromagnetic coupling manners, while the lateral displacement Ly leads to the splitting of plasmon resonance mode, which results from two different electromagnetic coupling manners. Our study gives an insight into the physical mechanism of plasmon resonances in two graphene hole arrays, and our findings may hold great promise in designing graphene-based plasmonic devices and metamaterials.

Low-temperature thermal conductance in three-dimensional nanowire embedded with phonon cavity

In this paper, we investigate low-temperature thermal conductance in three-dimensional nanowire embedded with phonon cavity based on the full scalar model of elasticity. The results show that at very low temperatures, the cavity can enhance the thermal conductance in certain lateral-width range, just as the constructive coupling of more phonon-modes excited in the cavity with modes in the transport region. At higher temperatures, however, the scattering of more interfaces formed from the cavity become a dominant factor to suppress the phonon transmission. Moreover, it is found that while the material in the cavity is substituted for the material with higher sound velocity than that in the transport region, the thermal conductance is also enhanced.