We present a compact physics-based model of the current-voltage characteristics of graphene field-effect transistors, of especial interest for analog and radio-frequency applications where bandgap engineering of graphene could be not needed. The physical framework is a field-effect model and drift-diffusion carrier transport. Explicit closed-form expressions have been derived for the drain current covering continuosly all operation regions. The model has been benchmarked with measured prototype devices, demonstrating accuracy and predictive behavior. Finally, we show an example of projection of the intrinsic gain as a figure of merit commonly used in RF /analog applications.
Electronic sensors based on graphene have a high potential in many applications, due to the unique properties of the graphene material. This study is a review where the authors discuss the properties of graphene which are useful to sensing applications and they report and describe different types of graphene electronic sensors: biological, mechanical, gas and chemical sensors. They also discuss the ways to functionalise graphene and the used device structures. They compare the performance of the main types of biological, mechanical and chemical sensors. Finally, they explain the future challenges of graphene-based sensors, in order to make graphene sensing systems and smart sensors, which would be their main breakthrough application. 1 Motivation and background After the award of the 2010 Nobel prize in Physics from 'groundbreaking experiments regarding the two-dimensional (2D) material graphene', there has been huge interest in using graphene for various applications including in electronics, photonics, displays, optoelectronics, photovoltaics, batteries and sensing. The significant amount of research work for the variety of applications is stimulated by graphene's exceptional material propertieselectrical, optical, thermal, mechanical and magnetic. Interested readers can consult [1-5] for an excellent introduction to graphene, its road map and what are some interesting applications of this amazing material. Graphene has several important properties including † Thinnest material making it suitable for flexible electronics, pressure sensors, electronic paper and so on. † Largest surface area per unit weight (∼2.7 × 10 3 m 2 /g) which is very important for sensing applications. † Excellent mechanical properties including being among the strongest material ever measured; extremely stiff and even stiffer than diamond; and very stretchable with up to ∼20% elasticity that are very important for sensors, flexible electronics and composites. † Record thermal conductivity that is higher than diamond for applications such as heat sinks to help alleviate thermal problems. † High current carrying capabilities, >10 2 higher than copper that makes it an exciting candidate for high-current density applications in nanoscale circuits. † Impermeable, for example, helium gas cannot get through which is important for nanofluidics and barriers. † Excellent electronic properties of very high intrinsic mobility; (>10 2 higher than silicon); charge carriers have zero rest mass; and long mean free path at room temperature on approximate millimetre range, properties that are critical for very high frequency electronics or terahertz imaging.
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