Sub-THz Characterisation of Monolayer Graphene

Research Article Sub-THz Characterisation of Monolayer Graphene Ehsan Dadrasnia, 1 Sujitha Puthukodan, 1 Vinod V. K. Thalakkatukalat hil, 1 Horacio Lamela, 1 Guillaume Ducournau, 2 Jean-Francois Lampin, 2 Frédéric Garet, 3 and Jean-Louis Coutaz 3 Optoelectr onics and Laser T echnology Group (GOTL), Carlos III de Madrid University, Leganes, Madrid, Spain IEMN, UMR CNRS , University of Lille, Avenue Poincar ´ e, BP , Villeneuve d’Ascq, France IMEP-LAHC, UMR CNRS , Univers ity of Savoie, Le Bourget du Lac Cedex, Fran ce Correspondence should be addressed to Horacio Lamela; [email protected] m.es Received December ; Accepted May ; Published July Academic Editor: Eugen Culea Copyright © Ehsan Dadrasnia et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We explore the optical and electrical characteristics o monolayer graphene by using pulsed optoelectr onic terahertz time-domain spe ctrosc op y in the re que ncy ra ngeo – GHz bas ed on ast dir ect mea sureme nt s o pha se andampl itude. We also sho w that these parameters can, however, be measured with higher resolution using a ree space continuous wave measurement technique associated with a vector network analyzer that offers a good dynamic range. All the scattering parameters (both magnitude and phase) are measured simultaneously. Te Nicholson-Ross-Weir method is implemented to extract the monolayer graphene parameters at the aorementioned requency range. 1. Introduction One-dimensional (D) carbon nanotubes (CNs) and two- dimensional (D) graphene orms o carbon nanostructures are considered as alternative materials to indium-tin oxide (IO) or exible transparent conductive lms, since they hav e uniqu e electri cal, optical, thermal, and mechanica l pro perties [–]. Car bon nan ostruc tur es hav e bee n appli ed in electronic devices, such as conductive exible adhesives [ ] and eld-effect transistors [ ]. Te high mobility o electrons [] and opt ica l con ductivit y [] in grap hene ha ve bee n exper - imentally investigated to study the ultraast intra-/interband transitions o two-dimensional Dirac ermions and ballistic transport at room temperature [ , ]. Contact devices have bee n emp loy ed to cha rac terize the cur ren t vol tag e o met alli c and semiconducting carbon nanostructure samples and to determine their remarkable electrical properties [ , ]. Many materials that are opaque to visible and inrared light are transparent to terahertz (Hz) radiation. Moreover , microwave and ar inrared (IR) absorption spectroscopy have limitations because o the complicated numerical trans- orma tion proce ss. Te nond estru ctive and nonco ntact opto - electr onic setups that generat e and detect coher ent Hz electr omagn etic wave s acili tate to char acterize both thin and bul k mat eri als . Te advan tag es o con tin uou s wave (CW) char acterization using vecto r netwo rk analy zer (VNA) over pulsed terahertz time-domain spectroscopy (Hz- DS) are higher spectral resolution and huge dynamic range in the sub- Hz requen cies (– dB around GHz) [ ]. For above GHz, pulsed Hz- DS offers better spectral resolution and dynamic range. Electrical properties, such as con ductiv ity , can be eas ily der ive d rom the measured opt ica l constants at Hz requencies [ , ]. I t wa s beli ev ed that the sy nt hesis o a single sheet graphene was difficult. But in , Novoselov and Geim show ed that it is possi ble to isola te monolaye r graph ene and to deposit it on a substrate and that the electrical and optical measurements can be perormed [ , ]. Here we present the experimental study o MG deposited on a used quart z substra te in the requency rang e o – GHz by Hindawi Publishing Corporation Journal of Spectroscopy Volume 2014, Article ID 601059, 6 pages http://dx.doi.org/10.1155/2014/601059

Documents

Sub-THz Characterisation of Monolayer Graphene