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In this article it iimplemented a set of circuit models to be exploited in conventional circuit simulators used in engineering degrees. The models capture the physics of the graphene-based transistors, characterized by the ambipolar conduction, and its resulting V-shaped transfer characteristics (current vs. gate voltage). These models can be exploited by the engineering students to explore ambipolar electronics opening the possibility to 1) redesigning and simplifying of conventional circuits; and 2)seeking of new functionalities in both analogue/RF and digital domains. In thisregard, as an example by just considering that the V-shaped transfer characteristicsbehaves as a parabola, we present new insights for the design of graphene-based RFpower amplifiers, mixers, phase shifters and frequency multipliers that specifically, En este trabajo, se implementan un conjunto de modelos que resuelven la física de los transistores basados en grafeno, capturando la conducción ambipolar y proporcionando las peculiares curvas de corriente frente a voltaje de puerta con forma de “V”. Estas herramientas pueden ser potencialmente utilizadas por estudiantes de ingeniería para explorar la electrónica ambipolar, abriendo la posibilidad de 1) rediseñar y simplificar aplicaciones de microondas convencionales; y 2) buscar nuevas funcionalidades en el ámbito analógico y de alta frecuencia. A este respecto, como ejemplo, presentamos nuevos enfoques para el diseño de multiplicadores de frecuencia, amplificadores de potencia, mezcladores y desfasadores en radiofrecuencia que específicamente aprovechan la ambipolaridad, PAIDI 2020 y de European Social Fund Operational Programme 2014–2020 no. 20804, Contrato PTA, con referencia PTA2020-018250-I

The progress made toward the definition of a modular compact modeling technology for graphene field-effect transistors (GFETs) that enables the electrical analysis of arbitrary GFET-based integrated circuits is reported. A set of primary models embracing the main physical principles defines the ideal GFET response under DC, transient (time domain), AC (frequency domain), and noise (frequency domain) analysis. Another set of secondary models accounts for the GFET non-idealities, such as extrinsic-, short-channel-, trapping/detrapping-, self-heating-, and non-quasi static-effects, which can have a significant impact under static and/or dynamic operation. At both device and circuit levels, significant consistency is demonstrated between the simulation output and experimental data for relevant operating conditions. Additionally, a perspective of the challenges during the scale up of the GFET modeling technology toward higher technology readiness levels while drawing a collaborative scenario among fabrication technology groups, modeling groups, and circuit designers, is provided., European Commission 881603, Spanish Government European Commission RTI2018-097876-B-C21 European Commission, Departament de Recerca i Universitat 001-P-001702

In this paper, the advances in radio-frequency (RF)/microwave biosensors based on graphene nanomaterials including graphene, graphene oxide (GO), and reduced graphene oxide (rGO) are reviewed. From a few frontier studies, recently developed graphene nanomaterials-based RF/microwave biosensors are examined in-depth and discussed. Finally, the prospects and challenges of the next-generation RF/microwave biosensors for wireless biomedical applications are proposed.

The quality of graphene in nanodevices has increased hugely thanks to the use of hexagonal boron nitride as a supporting layer. This paper studies to which extent hBN together with channel length scaling can be exploited in graphene field effect transistors (GFETs) to get a competitive radio frequency (RF) performance. Carrier mobility and saturation velocity were obtained from an ensemble Monte Carlo simulator that accounted for the relevant scattering mechanisms (intrinsic phonons, scattering with impurities and defects, etc.). This information is fed into a self consistent simulator, which solves the drift diffusion equation coupled with the two dimensional Poisson's equation to take full account of short channel effects. Simulated GFET characteristics were benchmarked against experimental data from our fabricated devices. Our simulations show that scalability is supposed to bring to RF performance an improvement that is, however, highly limited by instability. Despite the possibility of a lower performance, a careful choice of the bias point can avoid instability. Nevertheless, maximum oscillation frequencies are still achievable in the THz region for channel lengths of a few hundreds of nanometers., Comment: 29 pages, 7 figures, 1 table, Supplementary Information (10 pages) Funded by: 1 Micronova Nanofabrication Centre 2 European Union's Horizon 2020 (696656) 3 MINECO (TEC2013-42622-R, TEC2015-67462-C2-1-R, TEC2016-80839-P, MINECO/FEDER, FJCI-2014-19643) 4 MECD (CAS16/00043) 5 Generalitat de Catalunya (2014 SGR 384)

Channel length scaling in graphene field effect transistors (GFETs) is key in the pursuit of higher performance in radio frequency electronics for both rigid and flexible substrates. Although two-dimensional (2D) materials provide a superior immunity to Short Channel Effects (SCEs) than bulk materials, they could dominate in scaled GFETs. In this work, we have developed a model that calculates electron and hole transport along the graphene channel in a drift-diffusion basis, while considering the 2D electrostatics. Our model obtains the self-consistent solution of the 2D Poisson's equation coupled to the current continuity equation, the latter embedding an appropriate model for drift velocity saturation. We have studied the role played by the electrostatics and the velocity saturation in GFETs with short channel lengths L. Severe scaling results in a high degradation of GFET output conductance. The extrinsic cutoff frequency follows a 1/L^n scaling trend, where the index n fulfills n < 2. The case n = 2 corresponds to long-channel GFETs with low source/drain series resistance, that is, devices where the channel resistance is controlling the drain current. For high series resistance, n decreases down to n= 1, and it degrades to values of n < 1 because of the SCEs, especially at high drain bias. The model predicts high maximum oscillation frequencies above 1 THz for channel lengths below 100 nm, but, in order to obtain these frequencies, it is very important to minimize the gate series resistance. The model shows very good agreement with experimental current voltage curves obtained from short channel GFETs and also reproduces negative differential resistance, which is due to a reduction of diffusion current., 27-pages manuscript (10 figures) plus 6 pages of supplementary information. European Union Action H2020 (696656) / Department d'Universitats, Recerca i Societat de la Informaci\'o of the Generalitat de Catalunya (2014 SGR 384) / Ministerio de Econom\'ia y Competitividad of Spain (TEC2012-31330 and TEC2015-67462-C2-1-R) / MINECO FEDER

This thesis discusses the nanostructuration of local gates for electronic transport in graphene. The nanostructured gates enable a full control of the graphene doping profile at the Fermi wavelength scale which is the primary condition for Dirac Fermion optics experiments. This control of the doping profile proves to be necessary for the realization of high frequency transistors as well.In this work, I first present a new technology based on local bottom gates and high mobility graphene on thin boron nitride. This allows the realization of sharp and tunable p-n junctions which are the building blocks for Dirac Fermion optics. I will discuss a direct application of this technology, the Klein tunneling transistor, which takes advantage of the refractive properties of Dirac Fermions to open a transmission gap in graphene. Then this technology is implemented in a device with a gate located underneath the contact area in order to tune in situ the work function difference between the metal and the contacted graphene. The contact doping is monitored by measuring the resistance of the contact junction. In particular, the contact resistance is tuned and the polarity reversal of the contacted graphene is demonstrated.The last two chapters are devoted to the study of our devices when they are driven at high bias, which is the relevant regime for a high frequency transistor. In this regime, a current saturation is observed due to the electron-phonon inelastic scattering. From the current saturation measurement we extract the relevant phonon energy scale, pointing out a mechanism dominated by the surface phonons of the boron nitride substrate. In addition, we observe and model the non-uniform doping profile that arises in local gated devices at high bias which contributes also to the current saturation. Finally, the devices are measured in the gigahertz range to show how those current saturation mechanisms can improve the power gain of a graphene microwave transistor., Cette thèse traite du contrôle du profil de dopage dans le graphène au moyen de grilles locales nano-structurées, pour l’électronique des fermions de Dirac. Cette nano-structuration à l’échelle de la longueur d’onde de Fermi s’avère essentielle pour réaliser des expériences d’optique de fermion de Dirac ainsi que, dans un registre plus appliqué, pour l’électronique haute-fréquence. Dans ce travail, je commence par présenter notre technologie, qui repose sur des grilles arrières locales et du graphène haute-mobilité sur nitrure de bore hexagonal. Cela nous permet de réaliser des jonctions p-n abruptes, accordables et balistiques, qui sont l’élement de base pour l’électronique des fermions de Dirac. Je traiterai une application possible de cette technologie, le transistor à effet tunnel de Klein, qui utilise la réfraction des fermions de Dirac pour controler l’ouverture et la fermeture du canal d’un transistor graphène. Ensuite, cette technologie est mise en application pour équiper un transistor d’une grille placée sous le métal de contact. Cette grille de contact donne un contrôle complet du dopage du graphène contacté et permet de moduler la resistance de la jonction de contact jusque dans le gigahertz.Les deux derniers chapitres sont dévolus au régime de fort biais qui est pertinent pour les applications hautes fréquences ; dans ce régime le profile de dopage dépend aussi de la tension drain-source appliquée. Nous observons et modélisons la saturation de courant comme la conséquence de deux effets : la diffusion par les phonons de surface du substrat hBN et l’inhomogénéité de dopage dans les dispositifs à grilles locales. Enfin, nous évaluons les performances de nos dispositifs comme transistors radio-fréquences dans ce régime de saturation, notamment en terme de fréquence de coupure du gain de puissance.

Cataloged from PDF version of article. In this work, we present a method to probe molecular interactions on single-walled carbon nanotube (SWNT) surfaces using a surface plasmon sensor. SWNT networks were synthesized by chemical vapor deposition and transfer-printed on gold surfaces. We studied the excitation of surface plasmon-polaritons on nanotube coated gold surfaces with sub-monolayer, monolayer, and multilayer surface coverage. Integrating the fabricated sensor with a microfluidic device, we were able to obtain binding dynamics of a bovine serum albumin (BSA) protein on SWNT networks with various tube densities. The results reveal the kinetic parameters for nonspecific binding of BSA on SWNT coated surfaces having various tube densities. (C) 2012 American Institute of Physics.