Nanotube Field-effect Transistors Research Articles

A review of carbon nanotube field effect transistor from structure and properties to applications

Abstract. In the pursuit of next-generation electronic devices that overweigh the limitations of traditional silicon-based technologies, Carbon Nano Tube Field Effect Transistors (CNTFETs) have garnered significant attention. Unlike conventional Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), CNTFETs utilize the exceptional properties of Carbon Nanotubes (CNTs) as the channel material, promising substantial improvements in performance, power consumption, and scalability. This paper presents a comprehensive overview of CNTFETs, delving into their fundamental structures and underlying principles. It critically examines the unique characteristics that make CNTFETs an attractive alternative, including their superior carrier mobility, reduced leakage currents, and compatibility with nanoscale fabrication techniques. This review explores the application prospects of CNTFETs, spanning from high-speed digital circuits to energy-efficient sensors and beyond. Despite their promising potential, the paper also acknowledges recent challenges associated with CNTFETs, such as challenges in material synthesis, integration with existing semiconductor processes, and cost considerations. By addressing these challenges and fostering interdisciplinary research collaborations, the widespread adoption of CNTFETs in integrated circuits could revolutionize the electronics industry, enabling the development of more efficient, powerful, and sustainable devices for the future.

Reproducible, Accurate, and Sensitive Food Toxin On-Site Detection with Carbon Nanotube Transistor Biosensors.

Field-effect transistor (FET) biosensors based on nanomaterials are promising in the areas of food safety and early disease diagnosis due to their ultrahigh sensitivity and rapid response. However, most academically developed FET biosensors lack real-world reproducibility and comprehensive methodological validation to meet the standards of regulatory bodies. Here, highly uniform and well-packaged semiconducting carbon nanotube (CNT) FET biosensor chips were developed and assessed for the plug-and-play sensing for the rapid and highly sensitive detection of aflatoxin B1 (AFB1) in real food samples to meet international standards. In order to meet the requirements for reproducibility and stability, a scalable residual-free passivation and packaging process was developed for CNT FET biosensors. Portable detection systems were then constructed for on-site detection. The resulting packaged chips were functionalized with nucleic aptamers to enable highly selective detection of AFB1 in food samples with a detection limit (LOD) of 0.55 fg/mL (standard) for AFB1 and cross-reactivity coefficients to interferences as low as 1.8 × 10-7 in simulated solutions. Utilizing the portable detection system, on-site real food detection was achieved with a rapid response time less than 60 s, and LOD of 0.25 pg/kg (standard) in complex corn sample matrices. Single-blind tests demonstrated the ability of the chips to detect AFB1-positive food with 100% accuracy, using a set of 30 peanut samples. Validation experiments confirmed that the detection range, stability, and repeatability met international standards. This study showcased the accuracy, reliability, and potential practical applications of CNT FET biosensor chips in areas such as food safety and rapid biomedical testing.

Mass Production of Carbon Nanotube Transistor Biosensors for Point-of-Care Tests.

Low-dimensional semiconductor-based field-effect transistor (FET) biosensors are promising for label-free detection of biotargets while facing challenges in mass fabrication of devices and reliable reading of small signals. Here, we construct a reliable technology for mass production of semiconducting carbon nanotube (CNT) film and FET biosensors. High-uniformity randomly oriented CNT films were prepared through an improved immersion coating technique, and then, CNT FETs were fabricated with coefficient of performance variations within 6% on 4-in. wafers (within 9% interwafer) based on an industrial standard-level process. The CNT FET-based ion sensors demonstrated threshold voltage standard deviations within 5.1 mV at each ion concentration, enabling direct reading of the concentration information based on the drain current. By integrating bioprobes, we achieved detection of biosignals as low as 100 aM through a plug-and-play portable detection system. The reliable technology will contribute to commercial applications of CNT FET biosensors, especially in point-of-care tests.

Solution-processable low-voltage carbon nanotube field-effect transistors with high-k relaxor ferroelectric polymer gate insulator

Achieving energy-efficient and high-performance field-effect transistors (FETs) is one of the most important goals for future electronic devices. This paper reports semiconducting single-walled carbon nanotube FETs (s-SWNT-FETs) with an optimized high-k relaxor ferroelectric insulator P(VDF-TrFE-CFE) thickness for low-voltage operation. The s-SWNT-FETs with an optimized thickness (∼800 nm) of the high-k insulator exhibited the highest average mobility of 14.4 cm2 V−1s−1 at the drain voltage (I D) of 1 V, with a high current on/off ratio (I on/off >105). The optimized device performance resulted from the suppressed gate leakage current (I G) and a sufficiently large capacitance (>50 nF cm−2) of the insulating layer. Despite the extremely high capacitance (>100 nF cm−2) of the insulating layer, an insufficient thickness (<450 nm) induces a high I G, leading to reduced I D and mobility of s-SWNT-FETs. Conversely, an overly thick insulator (>1200 nm) cannot introduce sufficient capacitance, resulting in limited device performance. The large capacitance and sufficient breakdown voltage of the insulating layer with an appropriate thickness significantly improved p-type performance. However, a reduced n-type performance was observed owing to the increased electron trap density caused by fluorine proportional to the insulator thickness. Hence, precise control of the insulator thickness is crucial for achieving low-voltage operation with enhanced s-SWNT-FET performance.

ReS2-MoS2 heterojunction nanotube FET with superlattice structures for ultrasensitive detection of miRNA

Ultrasensitive detection of cancer biomarkers holds immense importance in facilitating the early diagnosis and treatment of cancer. Compared to conventional detection techniques, field-effect transistor (FET) biosensors have demonstrated substantial potential in achieving sensitive detection of cancer biomarkers. However, the ultrasensitive FET still remains great challenges due to the limited electron transport capacity and sensitivity of channel materials. Herein, we employed rhenium disulfide-molybdenum disulfide nanotube (ReS2-MoS2 NT) featuring superlattice structures as channel materials in FET biosensors for the highly sensitive detection of cancer biomarker miRNA-21. More concretely, ReS2-MoS2 NT featuring superlattice structures was synthesized using the anodic aluminum oxide (AAO) template sacrifice method and atomic layer deposition (ALD) method. The electrical properties of single ReS2-MoS2 NT FET were regulated by adjusting the total layers and number of heterojunction interfaces, and the optimal number of heterojunction interfaces of 7 was obtained. Finally, FET biosensors utilizing the network ReS2-MoS2 NT as the channel materials were fabricated and exhibited remarkable sensitivity in detecting miRNA-21 under an external light source. The linear range for detection spanned from 10 aM to 1 nM, with an exceptionally low detection limit of 2.1 aM. This study holds promise for replacing current channel materials and surpassing the detection threshold of cancer biomarkers in the future.

Presentation of Multi Inputs Full Ternary Comparator with Carbon Nano Tube Field Effect Transistor

Presentation of Multi Inputs Full Ternary Comparator with Carbon Nano Tube Field Effect Transistor

Performance Enhancement of CNFET-based Approximate Compressor for Error Resilient Image Processing

The approximate computing has emerged as an appealing approach to minimize energy consumption. By implementing inexact circuits at the transistor level, significant enhancements in various performance metrics such as power consumption, delay, energy, and area can be achieved. Consequently, researchers worldwide have been actively exploring the application of inexact techniques in circuit design. This paper introduces a novel technique for designing low-power digital circuits called extremely low power modified gate diffusion input (ELP-MGDI). This technique combines the principles of Modified Gate Diffusion Input with the utilization of Carbon Nano Tube Field-Effect Transistors (CNTFETs). The Objective of this paper is to enhance the power, delay, and area characteristics of a 4:2 compressor and multiplier by employing ELP-MGDI approach. To achieve this, we conducted thorough analysis and simulations using the Verilog-A simulator 32 nm CNFET technology Stanford University within the Cadence Virtuoso Tool. The results show extremely power, delay reduction and power-delay-product (PDP) of approximate multiplier has been improved by over 99%, and the circuit area has been reduced by 55%. The proposed processing module demonstrates superior performance compared to their conventional counterparts.

Based on the comparisons with various types of transistors to predict the trend of nanotube FETs in the future

With the improvement of new technology in electronic devices and the development of nanomaterials, higher better device performance and more efficient functions of Field-Effect Transistors (FETs) are expected, these require the use of material that has well-performed physical and chemical properties. Carbon nanotubes are a viable alternative, and their popularity is increasing rapidly in recent years. With the decrease in the size of the transistor, the increase in current, and the strength of magnetic and electrical fields, many problems for the creation of destructive and leaky currents occurred. This article mainly aimed to summarize three main FET types and included new carbon nanotube FETs by introducing their basic working mechanism and discussing the difficulties such as the short channel effect, gate-induced drain leakage and contact resistance. It also tries to give a few possible solutions to them which include adding a Lightly Doped Drain or using chemical doping, as well as predict how the potential of FETs in the future at the end.

Design of ternary full-adder and full-subtractor using pseudo NCNTFETs

Now-a-days, the binary logic system has intensified by scaling the field effect transistor (FET). However, due to the effectiveness of scaling the FET, ternary logics became more popular. Out of numerous ternary logic devices, carbon nanotube (CNT) FET (CNTFET) is considered a good candidate over silicon FETs. Hence, in this study, ternary schematics are developed based on Pseudo N-type CNTFETs. The ternary basic designs such as standard ternary inverter (STI), AND and OR gates are presented. Then, using the proposed basic logic gates, the complex designs such as full adder and full subtractor are also proposed. The HSPICE simulator is utilized to design proposed circuits and analyze different performance parameters. The performance such as delay, power and power delay product (PDP) are analyzed for the proposed circuits. Moreover, the proposed schematics performances are also compared to complementary schematics. It investigated that Pseudo N-type CNTFET schematics improved the overall performance on an average up to 65.82% over the complementary ternary circuits.

(Invited) Application of Machine Learning in Carbon Nanotube-Based Biosensors

Among electrochemical sensors, electrolyte-gated field-effect transistor (FET) with semiconducting single-walled carbon nanotubes (SWCNTs) is one of the most promising choices for the ultrasensitive biosensors. The biosensing is typically based on the recognition of analytes with capture probes (antibody, aptamer, receptor, enzyme, etc.) attached to SWCNTs. While the capture probes improve the chemical sensitivity and selectivity, the stability of the nanotube-based biosensors is limited by the activity of the capture probes. Another approach involves sensor arrays with different metal nanoparticles/self-assembled monolayers on the SWCNTs that act as nonspecific receptors. These sensor arrays can be trained with machine learning algorithms to distinguish analytes.When analytes bind to the sensor surface and interact with the semiconducting SWCNTs, they can cause modulations of the number of charge carriers in the FET channel, changing the device conductance, and eventually result in change in the FET characteristics, i.e., measured source-drain current vs. applied gate voltage. Rich information regarding the biorecognition process, sensing mechanism and sensing performances can be extracted from the changes in FET transfer characteristics. We proposed 11 features that can be selected to accurately describe the changes in FET transfer curves, including (1) relative change in transconductance, (2) threshold voltage (Vth) shift, (3, 10) relative change in conductance at ±0.6 Vg, (4-9) change in overall conductance normalized to conductance at Vth, and (11) the relative change in minimum conductance (see figure below). The transfer characteristics were extracted as distinct features for model training using established machine learning algorithms.We fabricated SWCNT-FET array functionalized with gold nanoparticles and different self-assembled monolayers (dodecanethiol and lipoic acid) for the sensing of nonmalignant and malignant cells, which were classified by linear discriminant analysis.[1] We have also demonstrated that the SWCNT-FET sensor array could be used for the screening of cell behaviors, and that live/dead mouse B16 melanoma cells could be successfully classified with machine learning.[2] [1] Silva, G. O.; Michael, Z. P.; Bian, L.; Shurin, G. V.; Mulato, M.; Shurin, M. R.; Star, A., Nanoelectronic Discrimination of Nonmalignant and Malignant Cells Using Nanotube Field-Effect Transistors. ACS Sens. 2017, 2, 1128–1132.[2] Liu, Z. R.; Shurin, G. V.; Bian, L.; White, D. L.; Shurin, M. R.; Star, A., A Carbon Nanotube Sensor Array for the Label-Free Discrimination of Live and Dead Cells with Machine Learning. Anal. Chem. 2022, 94, 3565-3573. Figure 1

Design of (3,2) and (4,2) CNTFET Ternary Counters for Multipliers

The reduction trees of combinational multipliers are widely applying counters. To be able to compare the ternary and the binary approaches, Nanotube Field-Effect Transistor (CNTFET) ternary (3,2) and ternary (4,2) counters have been designed. The ternary (4,2) counter is compared with the binary (7,3) counter as both compute approximately the same amount of information. The binary counter is more efficient. However, comparing counters is not enough: in the Wallace reduction tree of the ternary multiplier, there are two times more lines to reduce compared to the binary one, as a 1-trit multiplier generates both product and carry terms. Comparing the Wallace tree of an 8*8-trit multiplier and a 12*12-bit binary one also shows that the binary implementation is the most efficient.

Semiconducting SWCNT Photo Detector for High Speed Switching Through Single Halo Doping

The method opted for accuracy, and no existing studies are based on this method. A design and characteristic survey of a new small band gap semiconducting Single Wall Carbon Nano Tube (SWCNT) Field Effect Transistor as a photodetector is carried out. In the proposed device, better performance is achieved by increasing the diameter and introducing a new single halo (SH) doping in the channel length of the CNTFET device. This paper is a study and analysis of the performance of a Carbon Nano Tube Field Effect Transistor (CNTFET) as a photodetector using the self-consistent Poisson and Green function method. The 2D self-consistent Poisson and Green’s function method for various optical intensities and wavelength simulate this proposed photodetector. The performance study is based on the simulation of drain current, transconductance, sub-threshold swing, cut-off frequency, gain, directivity, and quantum efficiency under dark and illuminated conditions. These quantum simulation results show that cut-off frequency increases while there is an increase in diameter. The proposed SH-CNTFET provides better performance in terms of higher gain and directivity than conventional CNTFET (C-CNTFET). This device will be helpful in optoelectronic integrated circuits (OEIC) receivers due to its superior performance.

Comparative Analysis of Vertical Nanotube Field Effect Transistor (NTFET) Based on Channel Materials for Low Power Applications

3D Vertical Nanotube Field Effect Transistors (NTFETs) with various channel materials are analysed for 5nm gate length (LG) in this research work. The DC and RF studies are performed on NTFET devices with Silicon, Gallium Nitride (GaN), and SiliconGermanium (SiGe) as channel materials. The impact of variation of channel length, channel thickness, and temperature analysis on these devices have been studied. The ION/IOFF ratio of Si-NTFET, GaN-NTFET and SiGe-NTFET are found to be 2.7×108^ , 1.08×10^9 , 1.69×10^8 respectively. GaN channel NTFET exhibits the lowest subthreshold swing (SS) of 33.1mV/dec with the highest cut-off frequency of 190 GHz. From the analysis, it is found that NTFET with GaN channel device outperforms the other two devices.

Bacterial Vaginosis Monitoring with Carbon Nanotube Field-Effect Transistors.

The ability to rapidly and reliably screen for bacterial vaginosis (BV) during pregnancy is of great significance for maternal health and pregnancy outcomes. In this proof-of-concept study, we demonstrated the potential of carbon nanotube field-effect transistors (NTFET) in the rapid diagnostics of BV with the sensing of BV-related factors such as pH and biogenic amines. The fabricated sensors showed good linearity to pH changes with a linear correlation coefficient of 0.99. The pH sensing performance was stable after more than one month of sensor storage. In addition, the sensor was able to classify BV-related biogenic amine-negative/positive samples with machine learning, utilizing different test strategies and algorithms, including linear discriminant analysis (LDA), support vector machine (SVM), and principal component analysis (PCA). The biogenic amine sample status could be well classified using a soft-margin SVM model with a validation accuracy of 87.5%. The accuracy could be further improved using a gold gate electrode for measurement, with accuracy higher than 90% in both LDA and SVM models. We also explored the sensing mechanisms and found that the change in NTFET off current was crucial for classification. The fabricated sensors successfully detect BV-related factors, demonstrating the competitive advantage of NTFET for point-of-care diagnostics of BV.

Design of CNTFET based Domino Wide OR Gates using Dual Chirality for Reducing Subthreshold Leakage Current

The leakage current is prime concern in the modern portable battery operated device. Therefore, various techniques using MOSFET and FinFET devices are presented and their performance is evaluated and compared. To further reduce the leakage current for improved battery backup in portable devices, new devices namely Carbon Nano Tube Field Effect transistors (CNTFETs) can be used for design of different digital circuits. In this paper, subthreshold leakage power of dual chiral CNTFET based domino circuit is investigated and also the results are compared with single chiral CNTFET domino circuits. For better performance, threshold voltage of CNTFET in critical path is varied by changing the diameter or chirality of carbon nanotube. The subthreshold leakage power saving is observed in dual chiral standard and LECTOR based domino circuits for OR2, OR4, OR8 & OR16 for low temperature (25 °C) and high temperature (110 °C) with low and high input ranges. For high temperature & high input ranges, the simulation results show power saving from 89.65—97.86% and from 91.85—99.76% when compared with single chiral standard and LECTOR based domino circuits, respectively.

A Comprehensive Analysis of Short Channel Effects on Carbon Nano Tube Field Effect Transistors

As the direction of World health organization (WHO) report the diseases like male infertility, brain tumor, hearing impairment, fetus issues, effect on eyes and other various parts of the human body caused by harmful radiations released by portable electronic devices. To reduce radiation and size, a deep scaling has been applied on MOSFETs. Due to this aggressive scaling MOSFET devices are affected by Short Channel Effects (SCE) in Nanometer regime (&lt;10 nm). The Short Channel Effects Such as Subthreshold Swing (SS), Drain Induced barrier Lowering (DIBL) and threshold voltage roll-off (VT), plays a key role in determining the performance of CMOS devices. At Nano-meter scale Carbon Nano Tube FETs (CNTFETs) devices might be furnished with good control on leakage current and power consumption. The comparative analysis of Subthreshold Swing (SS), Drain Induced Barrier Lowering (DIBL) and Ion/Ioff ratio on Conventional Single Gate MOSFET (C-MOSFET), Double Gate MOSFET (DG-MOSFET) and CNTFET devices are presented in this paper. The results of comparative analysis show that CNTFET exhibits 133% times more Ion/Ioff ratio than MOSFET and very less change in Subthreshold swing and DIBL.

Olfactory receptor-based CNT-FET sensor for the detection of DMMP as a simulant of sarin

Dimetyl metylphosphonate (DMMP) is a simulant of sarin, which is a representative of nerve agents. Sarin is an organophosphorus toxic compound that is an inhibitor of acetylcholinesterase, paralyzing human neurotransmission and the autonomic nervous system. Detection of these nerve agents has been considered important for safety issues to prevent terrorism and to counter military threats. Although there have been various studies on sensors for detecting DMMP as a simulant of sarin, limitations still exist in specificity, sensitivity, and reliability. To overcome these limitations, we utilized a human olfactory receptor (hOR)-based single-walled carbon nanotube-field effect transistor (swCNT-FET) as a platform for the detection of DMMP. The hORs have high specificity for their certain target molecules. swCNT-FET can also convert biological signals of hORs to electrical signals with high sensitivity. By screening of hORs, hOR2T7 with high selectivity for DMMP was selected, and it was produced for development of the hOR2T7-conjugated bioelectronic nose (hOR2T7 B-nose). A hOR2T7 B-nose was able to selectively detect DMMP at a concentration of 10 fM. This shows ultrasensitive and selective performance for the detection of DMMP as a tool for sensing chemical warfare agents (CWAs), which could be used for practical applications in the field of safety.

Elastomeric Nanodielectrics for Soft and Hysteresis-Free Electronics.

Elastomeric dielectrics are crucial for reliably governing the carrier densities in semiconducting channels during deformation in soft/stretchable field-effect transistors (FETs). Uncontrolled stacking of polymeric chains renders elastomeric dielectrics poorly insulated at nanoscale thicknesses, thereby thick films are usually required, leading to high voltage or power consumption for on/off operations of FETs. Here, layer-by-layer assembly is exploited to build 15-nm-thick elastomeric nanodielectrics through alternative adsorption of oppositely charged polyurethanes (PUs) for soft and hysteresis-free FETs. After mild thermal annealing to heal pinholes, such PU multilayers offer high areal capacitances of 237nF cm-2 and low leakage current densities of 3.2 × 10-8 A cm-2 at 2V. Owing to the intrinsic ductility of the elastomeric PUs, the nanofilms possess excellent dielectric properties at a strain of 5% or a bending radius of 1.5mm, while the wrinkled counterparts show mechanical stability with negligible changes of leakage currents after repeated stretching to a strain of 50%. Besides, these nanodielectrics are immune to high humidity and conserve their properties when immersed into water, despite their assembly occurs aqueously. Furthermore, the PU dielectrics are implemented in carbon nanotube FETs, demonstrating low-voltage operations (< 1.5V) and negligible hysteresis without any encapsulations.

Ultra-Low Power 8-Transistor Modified Gate Diffusion Input Carbon Nano-Tube Field Effect Transistor Full Adder

An ultra-low power 8-Transistor Modified Gate Diffusion Input (MGDI) Carbon Nano Tube Field Effect Transistor (CNTFET) Full Adder (FA) has been presented in this paper. The proposed 8-T MGDI CNTFET Full Adder outperforms other adders in terms of Power Consumption, Propagation Delay and the PDP at different levels of Power Supply and Temperatures. The power consumption of the proposed 10 nm CNTFET 8-T MGDI Full Adder at 27°C is 1.96 nW. The proposed CNTFET FA exhibits 60.32% improvement in Power Consumption when compared to the existing 10 nm FINFET 8-T MGDI Full Adder. The propagation Delay of the proposed FA is 42.16 ps and an improvement of 57.68% is noticed over the existing FA. The Power Delay Product of the proposed 10 nm CNTFET 8-T MGDI FA is 82.63 × 10−21 Jules, whereas the PDP of the 10 nm FINFET 8-T MGDI FA is 492.07 × 10−21 Jules. The PDP of the proposed 10 nm CNTFET 8-T MGDI Full Adder exhibits 83.21% improvement when compared to the 10 nm FINFET 8-T MGDI FA.

A study of emerging semi-conductor devices for memory applications

In this paper, a study of the existing SRAM (Static Random Access Memory) cell topologies using various FET (Field Effect Transistor) low power devices has been done. Various low power based SRAM cells have been reviewed on the basis of different topologies, technology nodes, and techniques implemented. The analysis of MOSFET(Metal Oxide Semiconductor Field Effect Transistor), FinFET( Fin Field Effect Transistor), CNTFET (Carbon Nano Tube Field Effect Transistor), and TFET (Tunnel Field Effect Transistor) based SRAM cells on the basis of parameters such as stability, leakage current, power dissipation, read/write noise margin, access time has been done. HSPICE, TCAD, Synopsys Taurus, and Cadence Virtuoso were some of the software used for simulation. The simulations were done from a few µms to 7nm technology nodes by different authors.