Source-drain Potential Research Articles

Field-Effect Transistors Based on Single-Layer Graphene and Graphene-Derived Materials.

The progress of advanced materials has invoked great interest in promising novel biosensing applications. Field-effect transistors (FETs) are excellent options for biosensing devices due to the variability of the utilized materials and the self-amplifying role of electrical signals. The focus on nanoelectronics and high-performance biosensors has also generated an increasing demand for easy fabrication methods, as well as for economical and revolutionary materials. One of the innovative materials used in biosensing applications is graphene, on account of its remarkable properties, such as high thermal and electrical conductivity, potent mechanical properties, and high surface area to immobilize the receptors in biosensors. Besides graphene, other competing graphene-derived materials (GDMs) have emerged in this field, with comparable properties and improved cost-efficiency and ease of fabrication. In this paper, a comparative experimental study is presented for the first time, for FETs having a channel fabricated from three different graphenic materials: single-layer graphene (SLG), graphene/graphite nanowalls (GNW), and bulk nanocrystalline graphite (bulk-NCG). The devices are investigated by scanning electron microscopy (SEM), Raman spectroscopy, and I-V measurements. An increased electrical conductance is observed for the bulk-NCG-based FET, despite its higher defect density, the channel displaying a transconductance of up to ≊4.9×10-3 A V-1, and a charge carrier mobility of ≊2.86×10-4 cm2 V-1 s-1, at a source-drain potential of 3 V. An improvement in sensitivity due to Au nanoparticle functionalization is also acknowledged, with an increase of the ON/OFF current ratio of over four times, from ≊178.95 to ≊746.43, for the bulk-NCG FETs.

An Aptamer-Functionalised Schottky-Field Effect Transistor for the Detection of Proteins.

The outbreak of the coronavirus disease 2019 (COVID-19) in December 2019 has highlighted the need for a flexible sensing system that can quickly and accurately determine the presence of biomarkers associated with the disease. This sensing system also needs to be easily adaptable to incorporate both novel diseases as well as changes in the existing ones. Here we report the feasibility of using a simple, low-cost silicon field-effect transistor functionalised with aptamers and designed to attach to the spike protein of SARS-CoV2. It is shown that a linear response can be obtained in a concentration range of 100 fM to 10 pM. Furthermore, by using a larger range of source-drain potentials compared with other FET based sensors, it is possible to look at a wider range of device parameters to optimise the response.

Electrochemical sensor using carbon nanotube composites for chronic-degenerative diseases diagnosis

Sensitive and selective detection for cancer biomarkers is critical in cancer clinical diagnostics. In this work, we report an electrochemical detection platform for the carbohydrate antigen tumor marker 15-3 (CA15-3). It is based on a composite material of poly [2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene] (MEH-PPV) and multi-walled carbon nanotubes (MWCNT), which deposited as active layer of an organic thin-film transistor. This layer was surface functionalized with the Anti-CA15-3 monoclonal antibody. The devices have a favorable electrical output response for VSD source-drain potentials between 0 to 5 volts, and VG as 8 volts. Once the antigen (CA15-3) is recognized by the antibody, the electrical response is diminished. The test has a linear response in the concentration range of 0–30 U mL - 1 of CA 15–3, with a lower detection limit of ~1 U mL - 1 and a stability of 90% with respect to the initial values after storing the device for two weeks. The method was successfully applied to the determination of CA15-3 in serum samples. Possibly, this used composite material has a greater scope and can be applied to another type of detection scheme.

Light-Emitting Transistors with High Color Purity Using Perovskite Quantum Dot Emitters.

The class of organic-inorganic lead halides with perovskite crystal structures has recently emerged as promising materials for a variety of practical optoelectronic applications. In particular, hybrid halide perovskite quantum dots possess excellent intrinsic optoelectronic properties such as high color purity (full width at half-maximum of 24.59 nm) and photoluminescence quantum yields (92.7%). In this work, we demonstrate the use of perovskite quantum dot materials as an emissive layer of hybrid light-emitting transistors. To investigate the working mechanism of perovskite quantum dots in light-emitting transistors, we investigated the electrical and optical characteristics under both p-channel and n-channel operation. Using these materials, we have achieved perovskite quantum dot light-emitting transistors with high electron mobilities of up to 12.06 cm2·V-1 s-1, high brightness of up to 1.41 × 104 cd m-2, and enhanced external quantum efficiencies of up to 1.79% operating at a source-drain potential of 40 V.

A Nano Sensor Array for Methyl Salicylate Detection in Gaseous Form

Pathogenic plant diseases can be recognized through volatile organic compounds (VOC) chemical markers that are emitted from the plant surface upon distress. The ability to detect biomarkers from distressed plants sensitively, selectively, accurately, and rapidly could be of enormous benefit to the agricultural industry and crop growers. Among the various VOC, Methyl Salicylate (MeSa) has been identified to be a fingerprint compound that can be used as chemical marker for early detection of diseased crops1,2. Carbon nanotube (CNT) based sensors have been long used in detection of molecular species, due to their extremely high surface to volume ratio, and their p-type semiconducting behavior when connected to metallic electrode3. In this work the development of a CNT-based amperometric gas sensor for MeSa has been undertaken. The CNT gas adsorption capabilities result from their hollow structure and nanometric dimensions. These properties are important for sensitivity as it allows for several molecules to adsorb on to the surface of the sensor. The detection of MeSa is done by monitoring the current flowing through the CNT under specific gate-drain and source-drain potentials. These potentials are determined by careful examination of the change in current under different gate potentials (Trans-conductance) and the change in current under different source-drain potentials. When the MeSa molecule is adsorbed to the CNT surface it behaves as an additional gate potential source and therefore changes the current in the CNT. Selectivity can be achieved with different surface modifications of the CNT. The surface modifications will change the potential the MeSa induces on the CNT, and thus gives a different current profile for the adsorption and desorption of the MeSa molecules to and from the CNT surface.

On the classical aspects of electrons tunnelling through a quantum dot via a driven lattice gas model in one dimension

A theoretical study of classical aspects, i.e.: density, current density, and average speed of electrons tunnelling through a quantum dot (QD) via a simple driven lattice gas model have been carried out. The main objective of this study is to determine some classical aspects of electron tunnelling through a QD using the driven lattice gas model. The study is conducted by considering a resemblance between the components of the QD with the components of the totally asymmetric simple exclusion process (TASEP) that consists of only a single site and open boundary conditions. The former consists of a source, an island, and a drain, which corresponds respectively to the left reservoir (i = 0), site i = 1, and the right reservoir (i = 2) of the latter. Explicit expressions of the density, current densities, and average speed for electrons tunnelling through the QD in the classical regime are obtained. At the steady state, the density of electrons tunnelling through the dot is 0.5 and the current density becomes v/2, where v is the speed of the electrons. Furthermore, the speed of the electrons may be obtained as functions of temperature and the difference between gate and source-drain potentials. For very low temperatures, the speed of electrons rapidly goes to zero pointing to the occurrence of Coulomb blockade.

A model of a metallic quantum nanotransistor with a Coulomb-blockage gate in “magic” Au55 and Ag55 nanocrystals with speed of 1011 Hz

A model of a parallel metallic quantum nanotransistor with a Coulomb-blockage gate in “magic” nanocrystals Au55 and Ag55 with the speed of 1011 Hz having sizes of 100 × 100 × 12 nm3 is suggested and calculated. It is shown that the gate-opening threshold for this model with the source-drain potential of 2.74 V is 0.2 V, and the total current of 2500 elementary single-electron nanotransistors connected in parallel is 2 × 10−5 A, which is comparable with a current in terahertz semiconductor nanotransistors. It is shown that the charge amplification coefficient is Kq ∼ 1, while the power amplification coefficient is Kw ∼ 13. When using the inductive-capacitive load, a similar nanotransistor could be an element of an integrated circuit—radiation generator with wavelength λ = 3–6 mm and specific power of ∼104 W/cm2 with efficiency of ∼85–90%.

Light beam induced current measurements on ZnO Schottky diodes and MESFETs

AbstractThe homogeneity of the Schottky barrier potential of reactively sputtered PdOy/ZnO Schottky contacts has been investigated by light beam-induced current measurements on the micrometer scale. It is found that a metallic capping layer, acting as an equipotential surface, is not necessary for PdOy/ZnO Schottky contacts in contrast to AgxO/ZnO Schottky diodes. Further, we probed the generated photocurrent of a ZnO-based metal-semiconductor field-effect transistor for a closed and open channel, respectively. The photocurrent is, in general, one order of magnitude larger for closed channel conditions. The position of maximum photocurrent generation shifts towards the drain for higher source drain voltages for closed channel conditions, whereas it is nearly independent of the source drain potential for an open channel.

Magnetic field induced two-channel Kondo effect in multiple quantum dots

We study the possibility of observing the two-channel Kondo physics in multiple planar quantum dot heterostructures in the presence of a strong in-plane magnetic field. We show that a fine tuning of the coupling parameters of the system and an external magnetic field may stabilize the two-channel Kondo critical point. We make predictions for the behavior of the scaling of the differential conductance in the vicinity of the quantum critical point, as a function of magnetic field, temperature, and source-drain potential.

Self-consistent modeling of longitudinal quantum effects in nanoscale double-gate metal oxide semiconductor field effect transistors

Ultrathin double-gate silicon-on-insulator transistors are studied in the quantum coherent limit. By treating electron-electron interaction on the level of a mean field approach, the density matrix of the device becomes diagonal when expressed in a basis that results from imposing scattering boundary conditions at the terminals. The self-consistent scattering wave functions are computed using a multisubband scattering matrix formalism. This allows us to retain the full dimensionality of the wave functions and eliminates the need for the adiabatic decomposition of the Schrödinger equation. Subband mixing is fully taken into account and a piecewise analytical representation of the wave functions can significantly reduce the number of sampling positions along transport direction. By self-consistent simulations the size of source-to-drain tunneling as a function of gate length is demonstrated for different body thicknesses. A strong forward bias is shown to increase the tunnel current due to the thinning of the source-drain potential barrier. The effect of channel orientation on the tunnel current is also discussed.

Self-Gating Effect in the Electron Y-Branch Switch

In an electron waveguide Y-branch switch the electrostatic field applied between two gates switches a current into either of two branches. A novel mode of operation is proposed. For finite source-drain potentials, the switching field is shown to be strongly influenced by the electrochemical potentials in the waveguides. For certain biasing schemes this can be used to achieve gain without external gates and their RC constants. This allows switching up into the THz range in this new class of gateless mesoscopic devices. Conditions for bistability and oscillation are derived.