Electromechanical Piezoresistive Sensing in Suspended Graphene Membranes

Monolayer graphene exhibits exceptional electronic and mechanical properties, making it a very promising material for nanoelectromechanical (NEMS) devices. Here, we conclusively demonstrate the piezoresistive effect in graphene in a nano-electromechanical membrane configuration that provides direct electrical readout of pressure to strain transduction. This makes it highly relevant for an important class of nano-electromechanical system (NEMS) transducers. This demonstration is consistent with our simulations and previously reported gauge factors and simulation values. The membrane in our experiment acts as a strain gauge independent of crystallographic orientation and allows for aggressive size scalability. When compared with conventional pressure sensors, the sensors have orders of magnitude higher sensitivity per unit area.Comment: 20 pages, 3 figure

An exact solution of the linearized Boltzmann transport equation and its application to mobility calculations in graphene bilayers

This paper revisits the problem of the linearized Boltzmann transport equation (BTE), or, equivalently, of the momentum relaxation time, momentum relaxation time (MRT), for the calculation of low field mobility, which in previous works has been almost universally solved in approximated forms. We propose an energy driven discretization method that allows an exact determination of the relaxation time by solving a linear, algebraic problem, where multiple scattering mechanisms are naturally accounted for by adding the corresponding scattering rates before the calculation of the MRT, and without resorting to the semi-empirical Matthiessen\u2019s rule for the relaxation times. The application of our rigorous solution of the linearized BTE to a graphene bilayer reveals that, for a non monotonic energy relation, the relaxation time can legitimately take negative values with no unphysical implications. We finally compare the mobility calculations provided by an exact solution of the MRT problem with the results obtained with some of the approximations most frequently employed in the literature and so discuss their accuracy

Discrete Geometric Approach for Modelling Quantization Effects in Nanoscale Electron Devices

This paper presents the solution of the Schrodinger-Poisson coupled problem for nanoscale electron devices obtained by means of the Discrete Geometric Approach (DGA). The paper illustrates a self-contained description of the DGA method for a Schrodinger-Poisson problem, discusses its implementation and compares the results of the DGA with respect to the ones obtained by the well established Pseudo-spectral (PS) method for two technologically relevant benchmark devices (i.e. a nanowire and a FinFET). Finally, the paper examines the merits of the DGA approach with respect to the Finite Differences (FD) and Finite Elements (FE), that are the most frequently used methods in the electron device community

Phonon Limited Uniform Transport in Bilayer Graphene Transistors

We report modeling results for low-field mobility and velocity saturation in bilayer graphene based on a newly developed semiclassical transport Monte-Carlo simulator validated by comparison with momentum relaxation time (MRT) calculations. We show that remote phonons originating in the dielectric stack are expected to strongly affect the mobility, although assessing their actual influence at high inversion charge requires the development of an accurate model for dynamic screening. When the applied bias opens the energy gap, the mobility is significantly reduced. The saturation velocity is expected to be as high as 3 7107 cm/s and less degraded than mobility by bandgap opening

Low-Field Mobility and High-Field Drift Velocity in Graphene Nanoribbons and Graphene Bilayers

In this paper we follow a semiclassical approach based on the Boltzmann Transport Equation (BTE) to simulate and compare with experiments the low-field mobility (\u3bc) and the high-field drift velocity (vd) of graphene nano-ribbons (GNRs) and graphene bilayers (GbLs). It is found that remote phonons originating in the substrate have a large impact on the mobility, whereas their impact on the saturation velocity is smaller than predicted by recently proposed simplified model