Variability Effects in Graphene: Challenges and Opportunities for Device Engineering and Applications

Abstract

Abstract-Variability effects in graphene can result from the surrounding environment and the graphene material itself, which form a critical issue in examining the feasibility of graphene devices for large-scale production. From the reliability and yield perspective, these variabilities cause fluctuations in the device performance, which should be minimized via device engineering. From the metrology perspective, however, the variability effects can function as novel probing mechanisms, in which the 'signal fluctuations' can be useful for potential sensing applications. This paper presents an overview of the variability effects in graphene, with emphasis on their challenges and opportunities for device engineering and applications. The discussion can extend to other thin-film, nanowire and nanotube devices with similar variability issues, forming general interest in evaluating the promise of emerging technologies.

Low-frequency 1/f noise in graphene devices

“…It is known that the level of 1/f noise in the "hopping" conductors increases with decreasing temperature [53][54], which is opposite to what is normally observed in regular conductors. Finally, variability effects in graphene, originating from environmental disturbance and material and process variations [55] have to be studied systematically and separated from the fundamental noise characteristics.…”

Effect of channel-width and chirality on graphene field-effect transistor based real-time biomolecule sensing

“…1a); 2) GFETs are DC biased, formed with either a back-gate or a liquid-gate dipped in the analyte, 10,18 and tested at room temperature (T =300 K); 3) The gate voltage V G modulates the graphene channel potential V CH by a capacitive voltage divider composed of the quantum capacitance C Q in series with either the gate insulator capacitance C INS (in back-gated FET) 19,23 or the double layer capacitance C DBL (in liquid-gated FET) 6,24 (Fig. 1b); 4) The realtime sensing signal is defined as the percentage change of the FET current (dI DS /I DS ) transduced by the amount of biomolecular charges (dQ) close to the graphene surface 10,14 (Fig.…”

“…20,21 Since GSFETs exposed in the analyte mostly operate in the diffusive transport regime at room temperature, 18 we can assume G to be proportional to the DC conductivity σ, yielding A GS …”

“…In the future, the role of device-to-device variations will be needed to further examine the ultimate promise of GFET-based biosensing with statistical significance. 18 In summary, we present a theoretical framework to study the effect of channel-width and chirality on GFET based real-time biomolecule sensing. Our data suggest that when GFET scales its channelwidth down to nanometer ranges, the resulting GNR-FETs would not degrade the sensing performance compared to that in GS-FETs.…”

“…6,7,11,13,15 This current tracing approach allows researchers to study the molecular dynamics in a biological environment, and may help develop biotechnologies in real-time molecule detection and live cell imaging. 16,17 To date, GFETs have been made of a graphene sheet (GS-FET, ∼µm width) or a graphene nanoribbon (GNR-FET, ∼nm width) as the device channel, 18 which features two-dimensional and quasi-onedimensional transport, respectively. In contrast to GS that has a zero bandgap, GNR has an effective energy bandgap that depends on its chirality.…”