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In this paper, the transport properties of the band-to-band-tunneling carbon nanotube field-effect transistors (BTBT-CNTFETs) under uniaxial strain are studied, with the nonequilibrium Green's function (NEGF) formalism. The effects of the uniaxial strain on the electrical properties, such as the ON current (I_ON), OFF current (I_OFF), I_ON/I_OFF ratio, subthreshold swing and intrinsic delay are evaluated. It was observed that the uniaxial strain has strong effects on the transport properties of these transistors. The results show that appropriate uniaxial strain, although degrades the ON current and the intrinsic delay, it also decreases the power consumption of the BTBT-CNTFETs and as a result can be used for low-power applications.

In this paper, a new structure was introduced for carbon nanotube (CNT) MOSFET transistors. The proposed structure was composed of two different nanotubes for the source/drain and channel regions. Electrical characteristics of this structure were investigated using nonequilibrium Green’s function approach. Results of the simulations demonstrated that the proposed hetero-structure had almost the same ON-current and much less OFF-current and as a result higher $I_{\mathrm{\text{ON}}}/I_{\mathrm{\text{OFF}}}$ ratio than the conventional homo-structure. Results of the comparison between switching behavior in equal $I_{\mathrm{\text{ON}}}/I_{\mathrm{\text{OFF}}}$ ratio showed that, although the proposed structure had longer delay, its power dissipation for every switching event was less than that of the conventional structure. A further comparison of the switching characteristic in equal ON-current values showed that the proposed structure enjoys from shorter delay and also consumes less power-delay product (PDP) when compared to the LDDS structure.

In this paper, using the non-equilibrium Green's function formalism (NEGF), the effect of the chirality of carbon nanotube (CNT) on the performance of the strained tunneling carbon nanotube field effect transistors (T-CNTFETs) has been investigated. In this work, all evaluations are done by this assumption that the ON current, I_ON, is the main performance metric in the T-CNTFETs. The uniaxial strain has been considered in this work. On the other hand, for constructing a transistor with a desired I_ON, a variety of CNTs with the appropriate uniaxial strain could be used. The results of doing some comparisons among these situations show that, the use of the small diameter CNTs with the appropriate uniaxial strain could lead to the transistors with the better switching behavior. Likewise, the use of the large diameter CNTs with the appropriate uniaxial strain could result to the transistors with a higher I_ON/I_OFF ratio.

A new class of emerging materials known as topological insulators (TIs), such as bismuth selenide $({\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3)$, has an insulating band gap in the bulk and gapless surface state protected by its intrinsic time-reversal symmetry. These TI materials have attracted great attention because of their possible prospects in electrical and optical applications. In this work, we have prepared the ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ nanostructure using the nanosecond (ns) pulse laser ablation in liquid environment to study the field effect transistor behavior. After the laser ablation, ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ nanostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy to reveal the surface morphology and structural information. The field effect transistor (FET) has been fabricated using ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ nanostructure by drop casting ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ suspension between two gold electrodes having a gap of 3 $\mu$m on $\mathrm{\text{Si}}/{\mathrm{\text{SiO}}}_2$ substrate and tested for FET at various gate voltages. The SEM clearly shows the formation of ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ nanoparticles of different size varying from 20 nm to 30 nm after the ns laser ablation treatment. This result is supported by UV-visible spectra, as indicated by the enhancement in absorption band. The experimental results showed that charge conduction due to electrons as charge carriers were possible in ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ nanoparticle FET. This work provides another approach to use ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ nanoparticle FET for the applications in optoelectronic devices.

The gas nanosensor of indium oxide nanowires in laser assisted approach, doped with tin and zinc for gas sensing and 1D growth purposes respectively, was reported. The nanowires were very sensitive to H₂S gas in low concentration of 20ppb gas at room temperature. The fast dynamic intensive and sensitive response to gas was in a few seconds with an on/off sensitivity ratio of around 10. The square cross-section indium oxide nanowires were fabricated through physical vapor deposition (PVD) mechanism and annealing approach. The field emission scanning electron microscopy (FESEM) observations indicated that the annealing temperature was vital in nanostructures’ morphology. The fabricated nanowires for the optimized annealing temperature in applied growth technique were around 60nm in diameter.

Self-assembled InAs QD dot-in-a-well (DWELL) structures were grown on GaAs substrate by MBE system, and heterojunction modulation-doped field effect transistor (MODFET) was fabricated. The optical properties of the samples show that the photoluminescence of InAs/GaAs self-assembled quantum dot (SAQD) is at 1.265 μm at 300 K. The temperature-dependence of the abnormal redshift of InAs SAQD wavelength with the increasing temperature was observed, which is closely related with the inhomogeneous size distribution of the InAs quantum dot. According to the electrical measurement, high electric field current–voltage characteristic of the MODFET device were obtained. The embedded InAs QD of the samples can be regard as scattering centers to the vicinity of the channel electrons. The transport property of the electrons in GaAs channel will be modulated by the QD due to the Coulomb interaction. It has been proposed that a MODFET embedded with InAs QDs presents a novel type of field effect photon detector.

Carbon nanotube field effect transistor (FET) type biosensors have been widely investigated as one of the promising platforms for highly sensitive personalized disease-monitoring electronic devices. Combined with high level cutting edge information technology (IT) infra systems, carbon nanotube transistor biosensors afford a great opportunity to contribute to human disease care by providing early diagnostic capability. Several key prerequisites that should be clarified for the real application include sensitivity, reliability, reproducibility, and expandability to multiplex detection systems. In this brief review, we introduce the types, fabrication, and detection methods of single-walled carbon nanotube FET (SWNT-FET) devices. As surface functionalization of the devices by which nonspecific bindings (NSBs) are efficiently prohibited is also another important issue regarding reliable biosensors, we discuss several key strategies about surface passivation along with examples of various biomolecules such as proteins, DNA, small molecules, aptamers, viruses, and cancer and neurodegenerative disease markers which have been successfully sensed by SWNT-FET devices. Finally, we discuss proposed detection mechanisms, according to which strategies for fabricating sensor devices having high sensitivity are determined. Two main mechanisms — charge transfer (or electrostatic gate effect) and Schottky barrier effect, depending on the place where biomolecules are adsorbed — will be covered.

Single-crystal ZnO nanowires are synthesized by direct oxidation of zinc particles in air at a temperature much lower than the melting temperature of zinc solids. This simple and low-cost technique produces dense and high-quality ZnO nanowires. SEM and TEM studies revealed that as-grown ZnO nanowires have a uniform diameter and defect-free single-crystal structure. The growth direction of ZnO nanowires is the a axis, which is different from the common growth direction of one-dimensional ZnO structure. Room temperature PL spectra of ZnO nanowires grown with different oxygen pressures indicated that the quality of ZnO nanowires grown in air is much better than that of wires grown at reduced oxygen pressure. The excellent property of ZnO nanowires grown in air was confirmed by electrical transport measurements of individual ZnO nanowire field effect transistors.

The performance of a nanoscale sensor is not limited by the sensitivity of the sensor itself but rather by the diffusion time required for target molecules to reach to the extremely small sensor surface. In this work, we developed a carbon nanotube device that performed the dual functions of concentrating and detecting microorganisms in a sample solution. The sensor surface area was increased by fabricating a carbon nanotube network device using thermal chemical vapor deposition and standard microfabrication techniques. The target Escherichia coli (E. coli) cells were concentrated at the sensor surface via dielectrophoretic concentration by the carbon nanotube network channels. After 10 min of collection, the chip was washed with ample amounts of a clean buffer solution, and only the E. coli cells that were bound to the antibodies remained on the sensor surface. The binding of E. coli to the CNT network device decreased the conductance, presumably due to an increase in the scattering at the sensor surface. The detection limit and the time required for microorganism detection was greatly improved by combining dielectrophoresis with the carbon nanotube devices.

We report on the sensitive detection of glucose using silicon nanowire array field-effect-transistor (SiNW-FET) upon illumination. The uniformly distributed and size-controlled SiNWs were fabricated by "top-down" approach. The fabricated SiNW-FET device was evaluated for detection of glucose in the range of 100–900 mg/dL. The SiNW-FET shows enhanced sensitivity of 0.988 ± 0.030 nA (mg/dl)^-1 upon illumination at 480 nm light as compared to without illumination as 0.486 ± 0.014 nA (mg/dL)^-1. The presented SiNW-FET device is fast, stable and sensitive to light as well as to bio analyte, and hence can be utilized as sensitive biological sensing platform.

The photo-electrical properties of trilayer MoSe₂ nanoflakes, fabricated by mechanical exfoliation, were systematically studied in this paper. The trilayer MoSe₂ nanoflakes are n-type and possess a high gate modulation (On/Off ratio is larger than 10${}^5)$ and a relatively high carrier mobility (1.79cm${}^2{\mathrm{\text{V}}}^{-1}{\mathrm{\text{s}}}^{-1})$. The field effect transistor (FET) device of MoSe₂ shows sensitive photo response, high photoresponsivity ($R_{\lambda }=26.2$mA/W), quick response time ($t<20$ms), high external quantum efficiency ($\eta =5.1\%)$ and high detection rate ($D=2.7\times 10^9{\mathrm{\text{W}}}^{-1})$ for red and near-infrared wavelength. These results showed that the device based on few-layer MoSe₂ nanoflakes exhibited good photo-electrical properties, which might open a new way to develop few-layer MoSe₂-based material in the application of FETs and optoelectronics.