A 30-nm-gate field-effect transistor

The fabrication technology is developed for and characteristics are investigated of a GaAs Schottky-barrier field-effect transistor (SBFET) with an effective gate length of 30 nm. The SBFET power gain cutoff frequency is 150 GHz. The noise factor at 12–37 GHz is comparable with that of two-dimensional electron gas transistors. The theoretical electron transit time under the gate is below 0.1 ps.     

Graphene-like metal-on-silicon field-effect transistor

This paper presents a field-effect transistor with a channel consisting of a two-dimensional electron gas located at the interface between an ultrathin metallic film of Ni and a p-type Si(111) substrate. The gate length is L = 2 μm, its width is W = 180 μm, and the source-drain separation is 188 μm, the role of the gate dielectric being played by the surface states of the ultrathin metal layer. We have demonstrated that the two-dimensional electron gas channel is modulated by the gate voltage. The dependence of the drain current on the drain voltage has no saturation region, similar to a field-effect transistor based on graphene. The drain current is 2 mA at a drain voltage of 3 V and a gate voltage of 1.07 V, while the transconductance is 0.6 mS for a drain voltage of 6 V and a gate voltage of 1 V. However, the transport in this transistor is not ambipolar, as in graphene, but unipolar.     

Calibration method for a carbon nanotube field-effect transistor biosensor

An easy calibration method based on the Langmuir adsorption theory is proposed for a carbon nanotube field-effect transistor (NTFET) biosensor. This method was applied to three NTFET biosensors that had approximately the same structure but exhibited different characteristics. After calibration, their experimentally determined characteristics exhibited a good agreement with the calibration curve. The reason why the observed characteristics of these NTFET biosensors differed among the devices was that the carbon nanotube (CNT) that formed the channel was not uniform. Although the controlled growth of a CNT is difficult, it is shown that an NTFET biosensor can be easy calibrated using the proposed calibration method, regardless of the CNT channel structures.     

Biomimetic sensor for cAMP using an ion-sensitive field-effect transistor

A biomimetic sensor for cAMP was fabricated in combination with an ion-sensitive field-effect transistor (ISFET) as a transducer and a cAMP-imprinted polymer as a molecular recognition material. The cAMP-imprinted polymer was prepared using 1-allyl-2-thiourea as a functional monomer, and the binding ability and the selectivity of the polymer were evaluated. In addition, the imprinted polymer membrane was coated on the ISFET electrode, and the response of the sensor was evaluated. The cAMP-imprinted polymer showed high binding ability to and selectivity for cAMP in aqueous media. The linear relationship was obtained from 0.1 to 1.0 mM cAMP from the calibration curve in the cAMP-sensor.     

The other transistor: early history of the metal-oxidesemiconductor field-effect transistor

The silicon metal-oxide-semiconductor field-effect transistor (MOSFET or MOS transistor) did not become significant commercially until two decades after the 1948 announcement of the invention of the transistor by Bell Laboratories. The underlying concept of the MOSFET-modulation of conductivity in a semiconductor triode structure by a transverse electric field-first appeared in a 1928 patent application. It was confirmed experimentally in 1948. However early devices were not practical due to surface problems. Although these were solved at Bell Laboratories in 1958, Bell remained committed to earlier transistor technology. Development of the `other transistor' was first pursued elsewhere. It was finally the needs of computers and the opportunities created by integrated circuits that made the silicon MOSFET the basic element of late 20th-century digital electronics     

Quartz thermometer with a field-effect transistor oscillator

A very simple quartz thermometer is described which consists of a quartz temperature probe with practically linear temperature-frequency characteristic, an oscillator system and an electronic frequency meter. The thermometer measures temperatures from 233 to 373 K with an error < 0.02 K.     

Chemical sensing with ZnO nanowire field-effect transistor

Zinc oxide nanowires are configured as n-channel FETs. These transistors are implemented as chemical sensors for detection of various chemical gases. It is observed that the nanowire conductance is reduced when it is exposed to oxygen, nitrogen dioxide, ammonia gases at room temperature. Its ammonia sensing behavior is observed to switch from oxidizing to reducing when temperature is increased to 500 K. This effect is mainly attributed to the temperature dependent Fermi level shift. In addition, carbon monoxide is found to increase the nanowire conductance in the presence of oxygen. Furthermore, the detection sensitivity dependence on the nanowire radius is presented.     

High-on/off-ratio graphene nanoconstriction field-effect transistor

A method is reported to pattern monolayer graphene nanoconstriction field-effect transistors (NCFETs) with critical dimensions below 10 nm. NCFET fabrication is enabled by the use of feedback-controlled electromigration (FCE) to form a constriction in a gold etch mask that is first patterned using conventional lithographic techniques. The use of FCE allows the etch mask to be patterned on size scales below the limit of conventional nanolithography. The opening of a confinement-induced energy gap is observed as the NCFET width is reduced, as evidenced by a sharp increase in the NCFET on/off ratio. The on/off ratios obtained with this procedure can be larger than 1000 at room temperature for the narrowest devices; this is the first report of such large room-temperature on/off ratios for patterned graphene FETs.     

Ferroelectric field-effect transistor based on transparent oxides

We studied a Pb_xZr_1−xTiO₃/SnO₂/Al₂O₃ heterostructure as a base for transparent ferroelectric field-effect transistor. Single-crystal SnO₂/Al₂O₃ epitaxial films with the electron mobility of 25 cm²/V were grown by pulsed laser deposition using two YAG:Nd lasers. Depletion mode transistor Au/PZT/SnO₂/Al₂O₃ was produced by laser ablation and RF sputtering. All the samples demonstrate clockwise hysteresis of the source-drain characteristic. The energy distribution of traps at the PZT/SnO₂ interface was determined using a modified version of a transient current method. The effect of PZT intergrain boundaries on the retention time was taken into account for experimental data discussion.     

Surface cleaning of the nanowire field-effect transistor for gene detection

The efficiency of DNA immobilization by using various surface cleaning methods is studied in this work. The degree of surface cleaning is evaluated by the surface tension measurement to reveal the contribution from the polar and apolar terms. The observation from the fluorescent microscope images indicates the effectiveness of surface clean by the acetone and ethanol mixtures, as well as the sulphuric acid and hydrogen peroxide mixtures. We also fabricate a series of back-gated, 60-nm nanowired (NW) field-effect transistor (FET) sensors for mutation gene detection by following the developed acetone and ethanol mixtures. Electrical properties of the NWFET sensor demonstrate the n-channel depletion characteristics. The current of the sensor is reduced once the attachment of negative charge molecules. The single-stranded capture DNA is chemically immobilized onto the surface of silicon NWFET by three-step reactions. The sensor surface demonstrates the great performance of current shift after the suitable cleaning. The NWFET sensor is successfully applied to detect the BRAF(V599E) mutation genes from the hybridized processes. The sensing behaviour estimated from the electrical signal reaches the femtomolar level.     

Solution-processed top-contact electrodes strategy for organic crystalline field-effect transistor arrays

Organic crystals,especially ultra-thin two-dimensional(2D)ones such as monolayer molecular crystals,are fragile and vulnerable to traditional vacuum deposition.Up to now,most of the methods reported for fabricating organic field-effect transistors(OFETs)with top-electrodes on the 2D molecular crystals are based on mechanical-transfer method.Nondestructive method for large scale in-situ electrode deposition is urgent.In this work,the silver mirror reaction(SMR)is introduced to construct top-contact electrodes on 2D organic crystalline thin films.OFETs based on bilayer crystalline films with solution-processed silver electrodes show comparable performance to devices with transferred gold electrodes.In addition to that,OFETs with SMR fabricated silver electrodes show lower contact resistance than the ones with evaporated silver electrodes.Furthermore,the temperature under which SMR electrodes annealed is relatively low(60℃),making this approach applicable to varies of organic semiconductors,such as spin-coated polymer films,vacuum evaporated films,2D and even monolayer crystalline films.Besides,OFETs with sub-micrometer channel width and 25μm channel length are realized which might find practical application in the ultra-small pixel mini/micro-LEDs.     

Thermionic emission model for contact resistance in organic field-effect transistor

Injection mechanism of top-contact pentacene field-effect transistor (OFET) was investigated in respect to the internal field. The contact resistance was evaluated by the transmission line method for various applied external voltages as well as various pentacene film thicknesses. The behaviour of contact resistance was described in terms of the thermionic emission model (Schottky injection) and internal electric field generated by excess charges accumulated on pentacene–gate insulator interface. It was shown that pentacene film thickness changes the internal electric field affecting the carrier injection barrier. It was concluded that the space-charge field effect made a significant contribution for smaller pentacene film thicknesses and therefore in accordance to the thermionic model was able to decrease contact resistance representing the potential drop.     

A nanoparticulate indium tin oxide field-effect transistor with solid electrolyte gating

Reversible tuning of the transport properties of metallic conducting systems is not reported widely in the literature. Here, we report a junction field-effect transistor (FET) based on a transparent conducting oxide (TCO) nanoparticle channel and a solid polymer electrolyte as a gate. The device principle is based on the variation of the drain current induced by the capacitive double layer charging at the electrolyte/nanoparticle interfaces. A device with a metallic conducting channel made of indium tin oxide (ITO) nanoparticles exhibits an on/off ratio of 2 × 10(3) even when the gate potential is limited within the electrochemical capacitive region to avoid redox reactions at the interface. An FET device with metal-like conductance is always favored for the low dimensions of the device and a high on-state current. The field-effect mobility is calculated to be 24.3?cm(2)?V(-1)?s(-1). A subthreshold swing between 230 and 425?mV?dec(-1) is observed.     

High-performance carbon nanotube field-effect transistor with tunable polarities

State-of-the-art carbon nanotube field-effect transistors (CNFETs) behave as Schottky-barrier-modulated transistors. It is known that vertical scaling of the gate oxide significantly improves the performance of these devices. However, decreasing the oxide thickness also results in pronounced ambipolar transistor characteristics and increased drain leakage currents. Using a novel device concept, we have fabricated high-performance enhancement-mode CNFETs exhibiting n- or p-type unipolar behavior, tunable by electrostatic and/or chemical doping, with excellent OFF-state performance and a steep subthreshold swing (S=63 mV/dec). The device design allows for aggressive oxide thickness and gate-length scaling while maintaining the desired device characteristics.     

A combined virtual impactor and field-effect transistor microsystem for particulate matter separation and detection

Ambient suspended particulate matter(PM)(primarily with particle diameter 2.5m or less,i.e.,PM2.5)can adversely affect ecosystems and human health.Currently,optical particle sensors based on light scattering dominate the portable PM sensing market.However,the light scattering method has poor adaptability to different-sized PM and adverse environmental conditions.Here,we design and develop a portable PM sensing microsystem that consists of a micromachined virtual impactor(VI)for particle separation,a thermophoretic deposition chip for particle collection,and an extended-gate field-effect transistor(FET)for particle analysis.This system can realize on-site separation,collection,and analysis of aerosol particles without being influenced by environmental factors.In this study,the design of the VI is thoroughly analyzed by numerical simulation,and mixtures of different-sized silicon dioxide(SiO2)particles are used in an experimental verification of the performance of the VI and FET.Considering the low cost and compact design of the whole system,the proposed PM analysis microsystem has potential for PM detection under a wide range of conditions,such as heavily polluted industrial environments and for point-of-need outdoor and indoor air quality monitoring.     

Synthesis and characterization of anthracene derivative for organic field-effect transistor fabrication

Here we report on the synthesis and characterization of anthracene derivative for solution processable organic field-effect transistors. The transistor devices with bottom-contact geometry provided a maximum field-effect mobility of 3.74 x 10(-4) cm2 V(-1) s(-1) as well as current on/off ratio of 5.05 x 10(4) and low threshold voltage. Structural information in the solid state is obtained by thermal analysis and two-dimensional wide angle X-ray scattering (2D-WAXS). From the 2D-WAXS, it is clear that the planes of anthracene rings and benzene ring of the molecule are different in solid state. We assume similar arrangement in the thin-film which limit the effective hopping and thus charge mobility.     

Chemically sensitive field-effect transistor with polyaniline-ionic liquid composite gate

A sensing layer for a chemically sensitive field-effect transistor (CHEMFET) based on a composite of camphorsulfonic acid (CSA)-doped polyaniline (PANI) and the room-temperature ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)-imide, BMI(Tf2N), has been developed and characterized for the sensing of ammonia gas. The work function responses of the cast films with and without IL were analyzed by "stepwise" changes of ammonia gas concentration from 0.5 to 694 ppm in air as a function of the mole fraction of IL to PANI. The PANI x CSA/BMI(Tf2N) layers showed enhanced sensitivities, lower detection limits, and shorter response times. There is experimental evidence that PANI forms a charge-transfer complex with imidazolium cation.