Journal Article

Gate-tuning of graphene plasmons revealed by infrared nano-imaging

Andreev, G. O., Rodin, A. S., McLeod, A. S., Thiemens, M., Bao, W., Zhao, Z., Wagner, M., Fogler, M. M., Basov, D. N., Keilmann, F., Lau, C. N., Dominguez, G., Fei, Z., Neto, A. H. Castro, Zhang, L. M.

2012

Overview

Plasmons are directly launched in graphene, and their key parameters — propagation and attenuation — are studied with near-field infrared nano-imaging. Voltage-controlled graphene plasmonics Plasmonic devices, which exploit surface plasmons (electromagnetic waves that propagate along the surface of metals) offer the possibility of controlling and guiding light at subwavelength scales. All eyes are on graphene — atom-thick layers of carbon — as a promising platform for plasmonic applications because it can strongly interact with light and host surface plasmons in the infrared range. Two independent groups reporting in this issue of Nature show that plasmons can be directly launched in graphene, and observed with near-field optical microscopy. Moreover, the wavelengths and amplitudes of the plasmons can be tuned by a gate voltage, a promising capability for the development of on-chip graphene photonics for use in applications including telecommunications and information processing. Surface plasmons are collective oscillations of electrons in metals or semiconductors that enable confinement and control of electromagnetic energy at subwavelength scales 1 , 2 , 3 , 4 , 5 . Rapid progress in plasmonics has largely relied on advances in device nano-fabrication 5 , 6 , 7 , whereas less attention has been paid to the tunable properties of plasmonic media. One such medium—graphene—is amenable to convenient tuning of its electronic and optical properties by varying the applied voltage 8 , 9 , 10 , 11 . Here, using infrared nano-imaging, we show that common graphene/SiO 2 /Si back-gated structures support propagating surface plasmons. The wavelength of graphene plasmons is of the order of 200 nanometres at technologically relevant infrared frequencies, and they can propagate several times this distance. We have succeeded in altering both the amplitude and the wavelength of these plasmons by varying the gate voltage. Using plasmon interferometry, we investigated losses in graphene by exploring real-space profiles of plasmon standing waves formed between the tip of our nano-probe and the edges of the samples. Plasmon dissipation quantified through this analysis is linked to the exotic electrodynamics of graphene 10 . Standard plasmonic figures of merit of our tunable graphene devices surpass those of common metal-based structures.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/766/400/1021 / Collective excitations (including excitons, polarons, plasmons and other charge-density excitations) / Condensed matter: electronic structure, electrical, magnetic, and optical properties / Electric properties / Electromagnetic Fields / Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures / Electronic structure of nanoscale materials : clusters, nanoparticles, nanotubes, and nanocrystals / Exact sciences and technology / Experiments / Graphene / Graphite - chemistry / Humanities and Social Sciences / Imaging systems / Infrared Rays / Interferometry / letter / Methods / Microscopy, Atomic Force / multidisciplinary / Nanotechnology / Nanotechnology - methods / Optical properties / Physics / Plasmons (Physics) / Science / Science (multidisciplinary) / Standing waves / Static Electricity / Surface and interface electron states / Surface Properties / Technology application