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Operational Transconductance Amplifiers (OTAs) are the most pivotal blocks in analog circuits and systems. With the emersion of catastrophic short channel effects for Complementary Metal Oxide Semiconductor (CMOS) transistors at deep nanometric regime, the microelectronics scientists have focused on designing ultra-miniature OTAs based on non-silicon materials. During the last few years, Gate-All-Around Carbon Nanotube Field Effect Transistors (GAA-CNTFETs) with astonishing electrical and physical properties have drawn extensive attention of nanoelectronics researchers as a potential platform to represent high-performance nanoscale OTAs. In this regard, this work aims to propose an ultra-miniature ultra-wideband OTA based on the 10 nm GAA-CNTFET technology node. The proposed OTA benefits from the ballistic transport operation of the GAA-CNTFET transistors at ultra-scaled dimensions which provide a superior bandwidth (2.88 GHz) along with suitable power consumption (44.8 $$\upmu$$ W). The proposed OTA shows a 64.5 dB open-loop gain and a 59 dB common-mode rejection ratio at a 1 V supply voltage. Moreover, due to the utilization of the indirect feedback compensation method, the proposed GAA-CNTFET-based OTA presents an appropriate phase margin (61 $$^{\circ }$$ ) with a smaller compensator capacitor. With the mentioned performance metrics and occupying only 0.198 $$\upmu {\mathrm{m}^{2}}$$ physical area, the proposed GAA-CNTFET OTA has the potential to be considered as a replacement for nanoscale CMOS-based OTAs.

Based on the nonequilibrium Green’s function (NEGF) ballistic transport simulation, an optimized homojunction carbon nanotube (CNT) gate-all-around tunnel field effect transistor (GAA TFET) is proposed in this study. This TFET enhances the ON-state current and suppresses the ambipolarity extensively. By changing the channel diameter, gate length, and insulator thickness along with different values of doping levels and dielectrics of the source/channel/drain regions, a subthreshold swing $({SS})$ equal to ${11} ~\text {mV}/\text {dec}$ with an ON/OFF ratio of 108 is obtained at ${V}_{G}={V}_{D}={0.4}$ V. Source (drain) underlap/overlap with the gate is also considered in reaching an optimum result. Such advantages can be followed on other 1-D TFET devices and are explained in detail on the energy band diagram of the device.

This work reports on the optimization of factors affecting the performance of InSb-based quantum-well (QW) laser. The QW laser designs and its parameters are improved using physical modeling and simulation. The designed QWs can emit light at a range of 5.40–6.48 µm. The InAlSb is used as barrier between InSb active region and InAlAs cladding layer. To optimize the laser performance, the influence of Al concentration variation in barrier and cladding layers, as well as thickness of the active region on the QW, is investigated. The optical and electro-optical characteristics are compared with related experimental results. The output power, spontaneous emission and peak intensities versus injected current of the proposed QW structures demonstrate good similarity with similar reported grown samples. It is demonstrated that Auger recombination is truly reflected in the proposed QWs.

As the most attractive phosphors, the enhancement of the optical properties of single crystalline alkali halides such as KCl using different types of dopants was approached. Pure and doped KCl single crystals were grown using Czochralski method. Different activators such as Ag, In, Mn, and Sn ions were employed to enhance the optical properties of grown KCl single crystals. The structure of the single crystalline samples was investigated through X-ray diffraction (XRD). The optical properties of the samples were studied by employing UV–vis spectroscopy, photoluminescence (PL) analysis and ion beam-induced luminescence (IBIL), to confirm the incorporation of dopants into the host lattice. In the PL spectra of the samples, two UV and near UV emission lines and one red emission line were detected in the PL spectrum of the pure sample at 357 nm, 420 nm and 697 nm respectively that have not been reported before. Dopants led to the change in the intensity and position of the peaks. The peaks at 420 nm and 697 nm in the doped samples were shifted towards shorter wavelengths and a 500 nm emission was emerged due to impurities. The IBIL analysis proposed the violet color center for the Sn and Mn doped samples. These peaks turn the KCl single crystals into attractive phosphors.

This work provides a comparison of the changes in performance of a gate-all-around GAA carbon based tunnel field effect transistor p-i-n TFET and metal-oxide-semiconductor field effect transistor n-i-n MOSFET with respect to insulator thickness $\pmb{t_{ox}}$ values. The performance variations are prominent in the p-i-n TFET than n-i-n MOSFET structure; $\pmb{g_{d}}$ and $\pmb{g_{m}}$ are significantly degraded with $\pmb{t_{ox}}$ . The results are considered based on current spectrum on energy band diagram of the device in detail. Due to 1D quantum transport characteristics of CNTs the results could be applicable to any device with the same structure including 1D nanowire FET.

For a carbon nanotube field effect transistor (CNTFET) the ballistic I-V characteristics have been investigated theoretically with respect to ambient temperature for both the p-i-n tunnel FET (TFET) and n-i-n metal-oxide-semiconductor FET (MOSFET). The performance stability of a TFET at higher temperatures, especially in subthreshold regime in which the n-i-n device exhibits a devastating characteristic, is appreciable. Alongside very low subthreshold swing even at a temperature beyond 300 K, a p-i-n tunnel FET could be a more reliable choice for operating in a wide range of temperatures. The subthreshold swing, transconductance, output conductance, saturation mechanism and on/off current ratio are also considered with respect to CNT diameter as well. A lower diameter lessens some negative effects of operating at a high temperature. All the results can be realized based on the energy band diagram of the device and the Fermi functions of source and drain. This trend gives a valuable insight into exploring the changes in

Recent advances in etching agents and techniques on the fabrication of double-walled carbon nanotubes (DWCNTs) have introduced various techniques and devices based on nanotube technology. The present study evaluates the inter-shell interaction of DWCNT through density functional theory (DFT) and charge transfer model. The results showed that the band structure of a DWCNT is determined by super positioning of the band structures of the two individual CNT constituting the DWCNT. In next step, interwall conductance the electronic properties of DWCNT were studied through the band-structure approach. Our assessments have shown that at lower potentials the amount of intershell leakage current is negligible.

A theoretical study is presented on the on/off current ratio limits for a ballistic coaxially-gated carbon nanotube field effect transistor (CNTFET) with highly doped source/drain regions. Based on changes in gate insulator dielectric constant and thickness, the current ratio has been estimated at different ambient temperatures. Decreasing the gate insulator thickness after a certain value around 3 nm causes the current ratio to degrade drastically. Although the higher dielectric constant values have a fair effect on current ratio, this effect could be suppressed when the device with a low gate insulator thickness works at a low ambient temperature. The simulation results also show that the temperature drastically degrades the current ratio value; whereas in a certain range of ambient temperature, tuning the values of gate insulator thickness and dielectric constant could be very helpful. In this way, the optimum values of gate insulator thickness and dielectric constant are identified to offer the highest on/off current ratio of the device.

Quantum Cellular Automata (QCA) is an emerging technology at the nanotechnology level. The cryptogra- phy is an interesting application of QCA technology which has not been much mentioned yet. Utilizing the QCA technol- ogy, we have implemented the A5/1 stream cipher which was the original encryption algorithm for GSM. The implementa- tion of this cryptographic algorithm is accomplished by means of the implementation of its main modules. The main prop- erties of the implemented modules such as latency, area and complexity are discussed in this paper.

Carbon nanotubes are known as an interesting material to be used in the next generations of electronic technology, especially at nano regime. Nowadays, carbon nanotube field effect transistor or CNTFET is one of the promising devices for future electronic applications. A CNTFET which uses carbon nanotube as channel or source/drain region is the most promising candidate for replacing the current silicon transistor technology. The study of modern manufacturing approach and impact of device parameters on its performance is one of the important research fields in nanoelectronics. In this paper we study some aspects of changes in gate parameters at different channel diameters. This paper shows that for small values of diameter, increasing the dielectric constant of gate insulator doesn't help to improve the performance as value of dielectric constant of gate insulator reaches a certain amount. Also, increasing the oxide thickness of gate insulator doesn't always decrease transistor performance. For high diameter values, increasing the thickness up to a certain value improves the transistor performance.

Gas-sensing ability of n-type PtSi/porous Si Schottky junctions is investigated at room temperature. These junctions exhibit a breakdown-type current-voltage (I-V) curve at low reverse bias voltages (5-15 V) due to very large electric fringing fields (10/sup 5/-10/sup 6/ V/cm) developed at the sharp edges and the bottom of the pores. Experimental results for selected gases are presented. Gases with inherent dipole moments tend to decrease the breakdown voltage. Gases without dipole moments do not affect the I-V curve directly, but they can replace gas content inside the pores and decrease the dipole moment of the ambient gas, which results in an increase in breakdown voltage. Based on these experiments, the possible application of this structure as a gas sensor at room temperature is discussed.

This paper presents the design and simulation of an improved electro-thermal micromachined pump for drug delivery applications. Thermal actuators, which are a type of Micro Electro Mechanical system (MEMS) device, are highly useful because of their ability to deliver with great force and displacement. Thus, our structure is based on a thermal actuator that exploits the Joule heating effect and has been improved using the springy length properties of MEMS chevron beams. The Joule heating effect results in a difference in temperature and therefore displacement in the beams (actuators). Simulation results show that a maximum force of 4.4 mN and a maximum flow rate of 16 μL/min can be obtained by applying an AC voltage as low as 8 V at different frequencies ranging from 1 to 32 Hz. The maximum temperature was a problem at the chevron beams and the center shaft. Thus, to locally increase the temperature of the chevron beams alone and not that of the pumping diaphragm: (1) The air gaps 2 μm underneath and above the device layer were optimized for heat transfer. (2) Release holes and providing fins were created at the center shaft and actuator, respectively, to decrease the temperature by approximately 10 °C. (3) We inserted and used a polymer tube to serve as an insulator and eliminate leakage problems in the fluidic channel.

Choosing a suitable doping level of channel relevant to channel diameter is considered for determining the carbon nanotube field effect transistors' performance which seem to be the best substitute of current transistor technology. For low diameter values of channel the ratio of on/off current declines by increasing the doping level. But for higher diameter values there is an optimum point of doping level in obtaining the highest on/off current ratio. For further verification, the variations of performance are justified by electron distribution function's changes on energy band diagram of these devices. The results are compared at two different gate fields., Comment: 9 double spaced pages, 4 figures, published in applied physics letters, along with the terms of the American Institute of Physics Transfer of Copyright Agreement at first page

Carbon nanotube field effect transistors are the most promising candidate for replacing of current silicon transistor technology. Choosing a suitable dielectric constant for a specific temperature range is important in determining device performance. For higher dielectric constant, rising up the temperature causes current ratio to diminish, while at lower dielectric constants the current ratio increases. An interesting case is observed for transistors with dielectric constants in the middle range which exhibit an approximately constant current ratio for all ambient temperatures considered.

Nowadays carbon nanotube field effect transistor or CNTFET is one of the promising devices for future electronic applications. These transistors are frequently simulated using Non-Equilibrium Green's Function (NEGF) formalism. In this paper we study aspects of changes in gate parameters at different channel diameter which have not been known before. We find that in small values of diameter, increasing the dielectric constant of gate insulator doesn't help to improve the performance as value of dielectric constant reaches a certain amount. We also find that increasing the oxide thickness doesn't always decrease transistor performance. For high diameter values, increasing the thickness upto a certain value, improves the transistor performance.

Quantum cellular automata (QCA) represents an emerging technology at the nano technology level. Nowadays, many applications of QCA technology are introduced while programmability can increase the flexibility of QCA implementations. Using the structure of FPGAs can lead to flexible QCA implementations. So, we have implemented a MUX-Based FPGA CLB. This CLB has 3 multiplexers and each multiplexer is composed of 34 QCA cells.

Diamond thin films, 5 μm in thickness, were grown selectively on patterns of porous silicon by hot‐filament chemical vapor deposition (HFCVD). Monocrystalline p‐type silicon substrates, with (100) orientation and resistivity 5–15 Ω cm, were patterned by conventional photolithography to provide a photoresist mask for selective anodization. The polycrystalline diamond films thus formed were studied by scanning electron microscopy, x‐ray diffraction, and Raman spectroscopy which revealed high selectivity and high quality diamond films. This process proved to be simple and yet effective in developing patterns of diamond film in different shapes and sizes.

Carbon nanotube (CNT) could be exploited as a channel or source/drain region in field effect transistors (FETs). We theoretically investigate the impact of CNT doping level on a coaxially gated CNTFET's performance in the ballistic regime. The results show that the transconductance and subthreshold swing are independent of the CNT doping value. But threshold voltage and output conductance strongly depend on the channel doping level. It seems that the most important impact of CNT doping is the change in off-state current values resulting in a shift in the transfer characteristics of the device. However, it is possible to choose an optimal value of CNT doping to obtain the highest performance.

Although many researchers have studied boron-doped diamond thin films in the past several years, there have been few reports on the effects of doping CVD-grown diamond films with phosphorous. For this work, polycrystalline diamond thin films were grown by hot filament chemical vapor deposition (HFCVD) on p-type silicon substrates. Phosphorous was introduced into the reaction chamber as an in situ dopant during the growth. The quality and orientation of the diamond thin films were monitored by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Current-voltage (I-V) data as a function of temperature for golddiamond film-silicon-aluminum structures were measured. The activation energy of the phosphorous dopants was calculated to be approximately 0.29 eV.

Hot-filament chemical vapor deposited (HFCVD) boron doped polycrystalline diamond thin films having low volume resistivity were grown on sapphire. The films were characterized using scanning electron microscope (SEM), X-ray diffraction, and current-voltage measurements. SEM micrographs show good crystalline structure with preferred (100) orientation normal to the surface of the film. X-ray diffraction pattern revealed diamond characteristics with the four typical diamond peaks present. Finally, the obtained I-V characteristics indicated that the film's volume resistivity is at least two orders of magnitude lower than those of HFCVD polycrystalline diamond thin films grown on silicon under similar growth conditions.

Hot filament chemical vapor deposition (HFCVD) was utilized to grow high quality diamond film on porous silicon (PS) substrates to a thickness of 5–6 μm. Boron-doped silicon substrates of orientation and resistivity of 5–15 ohm-cm were anodized by the electrochemical process to form PS. A slurry of diamond paste (1/4 micron average grain size) was rubbed on the samples for a few seconds before introduction into the chamber. Diamond film growth on the PS has the advantages of shorter incubation time and higher nucleation density as evident from scanning electron microscopy (SEM). The results of X-ray diffraction confirm the growth of predominatly (111) oriented high quality diamond film. Electrical properties were also studied by sputtering circular gold contacts on top of diamond film and measuring current-voltage (I-V) characteristics.