Real-time detection of mercury ions in water using a reduced graphene oxide/DNA field-effect transistor with assistance of a passivation layer
Not Available
47 OTHER INSTRUMENTATION↗
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Results for “Transistors”
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Low-Temperature 2D/2D Ohmic Contacts in WSe 2 Field-Effect Transistors as a Platform for the 2D Metal–Insulator Transition
in this work, we report the fabrication of hexagonal-boron-nitride (hBN) encapsulated multiterminal WSe 2 Hall bars with 2D/2D low-temperature Ohmic contacts as a platform for investigating the two-dimensional (2D) metal-insulator transition. We demonstrate that the WSe 2 devices exhibit Ohmic behavior down to 0.25 K and at low enough excitation voltages to avoid current-heating effects. Additionally, the high-quality hBN-encapsulated WSe 2 devices in ideal Hall-bar geometry enable us to accurately determine the carrier density. Measurements of the temperature (T) and density (n s ) dependence of the conductivity σ(T, n s ) demonstrate scaling behavior consistent with a metalinsulator quantum phase transition driven by electron-electron interactions, but where disorder-induced local magnetic moments are also present. Our findings pave the way for further studies of the fundamental quantum mechanical properties of 2D transition metal dichalcogenides using the same contact engineering.
2D materials↗
Organic Field-Effect Transistors with a Bilayer Gate Dielectric Comprising an Oxide Nanolaminate Grown by Atomic Layer Deposition
In this work, we discuss top-gate OFETs with a bilayer gate dielectric comprising an Al 2 O 3 /HfO 2 nanolaminate layer grown by atomic layer deposition and an amorphous fluoro-polymer layer (CYTOP). Top-gate OFETs exhibit average carrier mobility values of 0.9 ± 0.2 cm 2 /(V s) and threshold voltage values of –1.9 ± 0.5 V and high operational and environmental stability under different environmental conditions such as damp air at 50 °C (80% relative humidity) and prolonged immersion in water at a temperature up to 95 °C.
36 MATERIALS SCIENCE↗
Field-Effect Transistors Based on Networks of Highly Aligned, Chemically Synthesized N = 7 Armchair Graphene Nanoribbons
Not Available
36 MATERIALS SCIENCE↗
Disorder from the Bulk Ionic Liquid in Electric Double Layer Transistors
Ionic liquid gating has a number of advantages over solid-state gating, especially for flexible or transparent devices and for applications requiring high carrier densities. But, the large number of charged ions near the channel inevitably results in Coulomb scattering, which limits the carrier mobility in otherwise clean systems. We develop a model for this Coulomb scattering. We then validate our model experimentally using ionic liquid gating of graphene across varying thicknesses of hexagonal boron nitride, demonstrating that disorder in the bulk ionic liquid often dominates the scattering.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Simple Formation of C60 and C60-Ferrocene Conjugated Monolayers Anchored onto Silicon Oxide with Five Carboxylic Acids and Their Transistor Applications
C{sub 60} and C{sub 60}-ferrocene conjugated molecule bearing five carboxylic acids successfully anchor onto a silicon oxide surface as a monolayer through a simple method of simply dipping an amino-terminated surface into the solution of the C{sub 60} derivatives. The monolayer structure was characterized by UV-vis spectroscopy, X-ray reflectivity, X-ray photoelectron spectroscopy, and IR spectroscopy to reveal that the molecules are standing presenting its C{sub 60} spherical face at the surface. The electronic effect of the C{sub 60} monolayer and the ferrocene-functionalized C{sub 60} monolayer in OFET devices was investigated. When an n-type OFET was fabricated on the ferrocene functionalized monolayer, we see an enhancement in the mobility. When a p-type OFET was made the ferrocene-functionalized C{sub 60} monolayer showed a lowering of the carrier mobility.
36 MATERIALS SCIENCE↗
Predictive process simulation of cryogenic implants for leading edge transistor design
Two cryogenic implant TCAD-modules have been developed: (i) A continuum-based compact model targeted towards a TCAD production environment calibrated against an extensive data-set for all common dopants. Ion-specific calibration parameters related to damage generation and dynamic annealing were used and resulted in excellent fits to the calibration data-set. (ii) A Kinetic Monte Carlo (kMC) model including the full time dependence of ion-exposure that a particular spot on the wafer experiences, as well as the resulting temperature vs. time profile of this spot. It was calibrated by adjusting damage generation and dynamic annealing parameters. The kMC simulations clearly demonstrate the importance of the time-structure of the beam for the amorphization process: Assuming an average dose-rate does not capture all of the physics and may lead to incorrect conclusions. The model enables optimization of the amorphization process through tool parameters such as scan speed or beam height.
36 MATERIALS SCIENCE↗
Comment on 'Investigation of the device instability feature caused by electron trapping in pentacene field effect transistors'[Appl. Phys. Lett. 100, 063306 (2012)]
No abstract prepared.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Scattering due to Schottky barrier height spatial fluctuation on two dimensional electron gas in AlGaN/GaN high electron mobility transistors
A scattering mechanism related to the Schottky barrier height (SBH) spatial fluctuation of the two dimensional electron gas (2DEG) in AlGaN/GaN heterostructures is presented. We find that the low field mobility is on the order of 10{sup 4}–10{sup 6} cm{sup 2}/Vs. The 2DEG transport properties are found to be influenced by both the mobility and 2DEG density variations caused by the SBH fluctuation. Our results indicate that a uniform Schottky contact is highly desired to minimize the influence of SBH inhomogeneity on the device performance.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Surface barrier height for different Al compositions and barrier layer thicknesses in AlGaN/GaN heterostructure field effect transistors
In this paper, we present a physics based analytical model for the calculation of surface barrier height for given values of barrier layer thicknesses and Al mole fractions. An explicit expression for the two dimensional electron gas density is also developed incorporating the change in polarization charges for different Al mole fractions.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Observation of localized states in atomically thin MoS{sub 2} field effect transistor
We present electrical transport and low frequency (1/f) noise measurements on mechanically exfoliated single, bi and trilayer MoS{sub 2}-based FET devices on Si/SiO{sub 2} substrate. We find that the electronic states in MoS{sub 2} are localized at low temperatures (T) and conduction happens through variable range hopping (VRH). A steep increase of 1/f noise with decreasing T, typical for localized regime was observed in all of our devices. From gate voltage dependence of noise, we find that the noise power is inversely proportional to square of the number density (∝ 1/n{sup 2}) for a wide range of T, indicating number density fluctuations to be the dominant source of 1/f noise in these MoS{sub 2} FETs.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Intrinsic device-to-device variation in graphene field-effect transistors on a Si/SiO{sub 2} substrate as a platform for discriminative gas sensing
Arrays of nearly identical graphene devices on Si/SiO{sub 2} exhibit a substantial device-to-device variation, even in case of a high-quality chemical vapor deposition (CVD) or mechanically exfoliated graphene. We propose that such device-to-device variation could provide a platform for highly selective multisensor electronic olfactory systems. We fabricated a multielectrode array of CVD graphene devices on a Si/SiO{sub 2} substrate and demonstrated that the diversity of these devices is sufficient to reliably discriminate different short-chain alcohols: methanol, ethanol, and isopropanol. The diversity of graphene devices on Si/SiO{sub 2} could possibly be used to construct similar multisensor systems trained to recognize other analytes as well.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Publisher's Note: “The behavior of off-state stress-induced electrons trapped at the buffer layer in AlGaN/GaN heterostructure field effect transistors” [Appl. Phys. Lett. 104, 033503 (2014)]
No abstract prepared.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Large Fermi energy modulation in graphene transistors with high-pressure O{sub 2}-annealed Y{sub 2}O{sub 3} topgate insulators
We demonstrate a considerable suppression of the low-field leakage through a Y{sub 2}O{sub 3} topgate insulator on graphene by applying high-pressure O{sub 2} at 100 atm during post-deposition annealing (HP-PDA). Consequently, the quantum capacitance measurement for the monolayer graphene reveals the largest Fermi energy modulation (E{sub F} = ∼0.52 eV, i.e., the carrier density of ∼2 × 10{sup 13} cm{sup −2}) in the solid-state topgate insulators reported so far. HP-PDA is the robust method to improve the electrical quality of high-k insulators on graphene.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Beyond modulation doping: Engineering a semiconductor to be ambipolar, or making an ON-OFF-ON transistor
Semiconductors are traditionaly either p-type or n-type, meaning that the mobile charge carriers in them are either 'holes' in the valence band or electrons in the conduction band. Ambipolar conduction implies that the experimenter should be able to populate the same channel with either electrons or holes in a controlled manner. This has been shown to be possible in newer materials like Graphene and some organic semiconductors. 'Ambipolarity' can open up new device possibilities as well as new ways to study fundamental scattering mechanisms in semiconductors. However, achieving this in a conventional high mobility structure like a GaAs-AlGaAs heterostructure/quantum well requires new thinking. It was realized, that to do this modulation doping must be given up and techniques to make an undoped heterostructure conduct, must be developed first. Such structures have been developed by only a few groups worldwide. They are of great interest to low temperature physicists working with Quantum Hall states and mesoscopic/nano structures in the ballistic regime. We discuss the reason behind this interest and the analysis of scattering mechanisms in such structures. Finally very recent experimental success in developing fully gate controlled ambipolar structures where both electron and hole mobilites exceed 1 million cm{sup 2}/Vs at low temperatures (T∼1Kelvin) are discussed. Such gated ambipolar structures can be used to analyse scattering mechanisms in ultra-high mobility 2dimensional electron and hole gases in a way that is not possible using other techniques.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Degradation of AlGaN/GaN high-electron mobility transistors in the current-controlled off-state breakdown
We investigate degradation mechanisms in AlGaN/GaN HEMTs which were repeatedly driven into the current-controlled off-state breakdown or subject to 60 s voltage- or current-controlled off state stresses. The current-controlled sweep in to the breakdown allows the sustainability of breakdown that can not be observed in the voltage controlled sweep. Only temporal changes were observed in the HEMT dc performance after repetitive sweeps, which were explained by charging/discharging of the HEMT surface at the gate-to-drain access region and in the GaN buffer below the gate. Similar changes were observed also if high-voltage stress has been applied on the drain; however, permanent degradation appears after 60 s current-controlled breakdown stress. In this case, the drain leakage current, as well as the breakdown current, increases significantly. On the other hand, the breakdown voltage, as well as the gate characteristics, remains unaltered. We suggest that the avalanche-injection process is governing the off-state breakdown event with a dominant role of the potential barrier at the channel-buffer interface.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Indium arsenide nanowire field-effect transistors for pH and biological sensing
Indium Arsenide is a high mobility semiconductor with a surface electron accumulation layer that allows ohmic electrical contact to metals. Here, we present nanowire devices based on this material as a platform for chemical and biological sensing. The sensing principle involves the binding of a charged species at the sensor surface transduced via field effect into a change in current flowing through the sensor. We show the sensitivity of the platform to the H{sup +} ion concentration in solution as proof of principle and demonstrate the sensitivity to larger charged protein species. The sensors are highly reproducible and reach a detection limit of 10 pM for Avidin.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗