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Graphene-Based One-Dimensional Terahertz Phononic Crystal: Band Structures and Surface Modes
- Source :
- Nanomaterials, Vol 10, Iss 11, p 2205 (2020)
- Publication Year :
- 2020
- Publisher :
- MDPI AG, 2020.
-
Abstract
- In this paper, we provide a theoretical and numerical study of the acoustic properties of infinite and semi-infinite superlattices made out of graphene-semiconductor bilayers. In addition to the band structure, we emphasize the existence and behavior of localized and resonant acoustic modes associated with the free surface of such structures. These modes are polarized in the sagittal plane, defined by the incident wavevector and the normal to the layers. The surface modes are obtained from the peaks of the density of states, either inside the bulk bands or inside the minigaps of the superlattice. In these structures, the two directions of vibrations (longitudinal and transverse) are coupled giving rise to two bulk bands associated with the two polarizations of the waves. The creation of the free surface of the superlattice induces true surface localized modes inside the terahertz acoustic forbidden gaps, but also pseudo-surface modes which appear as well-defined resonances inside the allowed bands of the superlattice. Despite the low thickness of the graphene layer, and though graphene is a gapless material, when it is inserted periodically in a semiconductor, it allows the opening of wide gaps for all values of the wave vector k// (parallel to the interfaces). Numerical illustrations of the band structures and surface modes are given for graphene-Si superlattices, and the surface layer can be either Si or graphene. These surface acoustic modes can be used to realize liquid or bio-sensors graphene-based phononic crystal operating in the THz frequency domain.
- Subjects :
- graphene
phonon
crystal
surface mode
resonant mode
Chemistry
QD1-999
Subjects
Details
- Language :
- English
- ISSN :
- 20794991
- Volume :
- 10
- Issue :
- 11
- Database :
- Directory of Open Access Journals
- Journal :
- Nanomaterials
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.809798d2531a487383c2c3f88d7a3b7a
- Document Type :
- article
- Full Text :
- https://doi.org/10.3390/nano10112205