Abstract- Transmission of Terahertz Acoustic Waves through Graphene-Semiconductor Layered Structures

http://scientificresearchpublishing.wordpress.com/2014/10/22/transmission-of-terahertz-acoustic-waves-through-graphene-semiconductor-layered-structures/

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http://www.scirp.org/journal/PaperInformation.aspx?PaperID=50635#.VEcXbVfHRK0

Author(s)

Shuhui Zhang1, Wen Xu1,2*, Francois M. Peeters3

Affiliation(s)

1Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei, China.
2Department of Physics, Yunnan University, Kunming, China.
3Department of Physics, University of Antwerp, Antwerpen, Belgium.

ABSTRACT

We present a theoretical study of the acoustic properties of graphene-semiconductor layered structures. The transmission coefficient for longitudinal acoustic waves through the structure is evaluated by using the usual transfer matrix method. We find that the finite thickness of the graphene layer can affect significantly the transmission spectrum of the proposed structure. The features of the sound transmittance depend strongly on the number of the graphene layers. For mul-ti-layer graphene-semiconductor structures, the sound transmission spectrum looks very similar to that for an ideal superlattice. For such structures, terahertz acoustic forbidden gap can be observed even when a thick semiconductor layer is considered. These results are the consequence of the Bragg’s condition for sound waves. This study is relevant to the exploration of the acoustic properties of graphene-based layered structures and to the application of graphene as high-frequency acoustic devices.

Abstract-Extraordinary terahertz absorption bands observed in micro/nanostructured Au/polystyrene sphere arrays

http://www.nanoscalereslett.com/

Guotao Duan, Fuhai Su, Wen Xu, Cunlin Zhang and Weiping Cai

Terahertz (THz) time-domain spectroscopy is carried out for micro/nanostructured periodic Au/dielectric sphere arrays on Si substrate. We find that the metal-insulator transition can be achieved in THz bandwidth via varying sample parameters such as the thickness of the Au shell and the diameter of the Au/dielectric sphere. The Au/polystyrene sphere arrays do not show metallic THz response when the Au shell thickness is larger than 10 nm and the sphere diameter is smaller than 500 nm. This effect is in sharp contrast to the observations in flat Au films on Si substrate. Interestingly, the Au/polystyrene sphere arrays with a 5-nm-thick Au shell show extraordinary THz absorption bands or metallic optical conductance when the diameter of the sphere is larger than 200 nm. This effect is related to the quantum confinement effect in which the electrons in the structure are trapped in the sphere potential well of the gold shell.