1,187 research outputs found
Correlation of p-doping in CVD Graphene with Substrate Surface Charges
Correlations between the level of p-doping exhibited in large area chemical vapour deposition (CVD) graphene field effect transistor structures (gFETs) and residual charges created by a variety of surface treatments to the silicon dioxide (SiO(2)) substrates prior to CVD graphene transfer are measured. Beginning with graphene on untreated thermal oxidised silicon, a minimum conductivity (σ(min)) occurring at gate voltage V(g) = 15 V (Dirac Point) is measured. It was found that more aggressive treatments (O(2) plasma and UV Ozone treatments) further increase the gate voltage of the Dirac point up to 65 V, corresponding to a significant increase of the level of p-doping displayed in the graphene. An electrowetting model describing the measured relationship between the contact angle (θ) of a water droplet applied to the treated substrate/graphene surface and an effective gate voltage from a surface charge density is proposed to describe biasing of V(g) at σ(min) and was found to fit the measurements with multiplication of a correction factor, allowing effective non-destructive approximation of substrate added charge carrier density using contact angle measurements
Small-signal model for 2D-material based field-effect transistors targeting radio-frequency applications: the importance of considering non-reciprocal capacitances
A small-signal equivalent circuit of 2D-material based field-effect
transistors is presented. Charge conservation and non-reciprocal capacitances
have been assumed so the model can be used to make reliable predictions at both
device and circuit levels. In this context, explicit and exact analytical
expressions of the main radio-frequency figures of merit of these devices are
given. Moreover, a direct parameter extraction methodology is provided based on
S-parameter measurements. In addition to the intrinsic capacitances,
transconductance and output conductance, our approach allows extracting the
series combination of drain/source metal contact and access resistances.
Accounting for these extrinsic resistances is of upmost importance when dealing
with low dimensional field-effect transistors.Comment: 8 pages, 10 figures, 4 table
Scalable Production of Highly-Sensitive Nanosensors Based on Graphene Functionalized with a Designed G Protein-Coupled Receptor
We have developed a novel, all-electronic biosensor for opioids that consists
of an engineered mu opioid receptor protein, with high binding affinity for
opioids, chemically bonded to a graphene field-effect transistor to read out
ligand binding. A variant of the receptor protein that provided chemical
recognition was computationally redesigned to enhance its solubility and
stability in an aqueous environment. A shadow mask process was developed to
fabricate arrays of hundreds of graphene transistors with average mobility of
~1500 cm2 V-1 s-1 and yield exceeding 98%. The biosensor exhibits high
sensitivity and selectivity for the target naltrexone, an opioid receptor
antagonist, with a detection limit of 10 pg/mL.Comment: Nano Letters 201
Electrolyte gate dependent high-frequency measurement of graphene field-effect transistor for sensing applications
We performed radiofrequency (RF) reflectometry measurements at 2.4 GHz on
electrolyte-gated graphene field-effect transistors (GFETs) utilizing a tunable
stub-matching circuit for impedance matching. We demonstrate that the gate
voltage dependent RF resistivity of graphene can be deduced even in the
presence of the electrolyte which is in direct contact with the graphene layer.
The RF resistivity is found to be consistent with its DC counterpart in the
full gate voltage range. Furthermore, in order to access the potential of
high-frequency sensing for applications, we demonstrate time-dependent gating
in solution with nanosecond time resolution.Comment: 14 pages, 4 figure
Graphene Gold Nanoparticle Hybrid Based Near Infrared Photodetector
This paper presents novel and simplistic approach towards the development of graphene based near infrared (NIR) photodetectors. The developed device comprises of Au nanoparticles integrated within the channel of the back-gated graphene field effect transistors. The introduction of Au nanoparticles enhanced response of the device under IR illumination due improved NIR absorption. Further, dynamic response of the device under IR illumination is presented. This study will trigger the development of novel hybrid graphene device for graphene based photodetectors in IR regime
- …