Single-walled Carbon Nanotube Field-effect Transistors Research Articles

Bioelectronic sensing platform emulating the human endocannabinoid system for assessing and modulating of cannabinoid activity

Cannabinoids are involved in physiological and neuromodulatory processes through their interactions with the human cannabinoid receptor-based endocannabinoid system. Their association with neurodegenerative diseases and brain reward pathways underscores the importance of evaluating and modulating cannabinoid activity for both understanding physiological mechanisms and developing therapeutic drugs. The use of agonists and antagonists could be strategic approaches for modulation. In this study, we introduce a bioelectronic sensor designed to monitor cannabinoid binding to receptors and assess their agonistic and antagonistic properties. We produced human cannabinoid receptor 1 (hCB1R) via an Escherichia coli expression system and incorporated it into nanodiscs (NDs). These hCB1R-NDs were then immobilized on a single-walled carbon nanotube field-effect transistor (swCNT-FET) to construct a bioelectronic sensing platform. This novel system can sensitively detect the cannabinoid ligand anandamide (AEA) at concentrations as low as 1 fM, demonstrating high selectivity and real-time response. It also successfully identified the hCB1R agonist Δ9-tetrahydrocannabinol and observed that the hCB1R antagonist rimonabant diminished the sensor signal upon AEA binding, indicating the antagonism-based modulation of ligand interaction. Consequently, our bioelectronic sensing platform holds potential for ligand detection and analysis of agonism and antagonism.

(Invited) Correlation Measurements for Carbon Nanotubes with Quantum Defects

Single-photon sources are one of the essential building blocks for the development of photonic quantum technology. In terms of potential practical application, an on-demand electrically driven quantum-light emitter on a chip is notably crucial for integrating photonic integrated circuits. Here, we propose functionalized single-walled carbon nanotube field-effect transistors as a promising solid-state quantum-light source by demonstrating photon antibunching behavior via electrical excitation. The sp3 quantum defects were formed on the surface of (7, 5) carbon nanotubes by 3,5-dichlorophenyl functionalization, and individual carbon nanotubes were wired to graphene electrode pairs. Filtered electroluminescent defect-state emission at 77 K was coupled into a Hanbury Brown and Twiss experiment setup, and single-photon emission was observed by performing second-order correlation function measurements. We discuss the dependence of the intensity correlation measurement on excitation power and emission wavelength highlighting the challenges of performing such measurements while simultaneously analyzing acquired data. Our results indicate a route toward room-temperature electrically-triggered single-photon emission.

Label-Free and Ultrasensitive Detection of Cartilage Acidic Protein 1 in Osteoarthritis Using a Single-Walled Carbon Nanotube Field-Effect Transistor Biosensor.

Osteoarthritis (OA), a prevalent degenerative joint disease, significantly affects the well-being of afflicted individuals and compromises the standard functionality of human joints. The emerging biomarker, Cartilage acidic protein 1 (CRTAC1), intricately associates with OA initiation and serves as a prognostic indicator for the trajectory toward joint replacement. However, existing diagnostic methods for CRTAC1 are hampered by the limited abundance, thus restricting the precision and specificity. Herein, a novel approach utilizing a single-walled carbon nanotube field-effect transistor (SWCNTs FET) biosensor is reported for the direct label-free detection of CRTAC1. High-purity semiconducting carbon nanotube films, functionalized with antibodies of CRTAC1, provide excellent electrical and sensing properties. The SWCNTs FET biosensor exhibits high sensitivity, notable reproducibility, and a wide linear detection range (1 fg/mL to 100 ng/mL) for CRTAC1 with a theoretical limit of detection (LOD) of 0.2 fg/mL. Moreover, the SWCNTs FET biosensor is capable of directly detecting human serum samples, showing excellent sensing performance in differentiating clinical samples from OA patients and healthy populations. Comparative analysis with traditional enzyme-linked immunosorbent assay (ELISA) reveals that the proposed biosensor demonstrates faster detection speeds, higher sensitivity/accuracy, and lower errors, indicating high potential for the early OA diagnosis. Furthermore, the SWCNTs FET biosensor has good scalability for the combined diagnosis and measurement of multiple disease markers, thereby significantly expanding the application of SWCNTs FETs in biosensing and clinical diagnostics.

Spintronic device in SWCNT-FET configuration based on chromium oxides thin films consisting of half-metallic ferromagnetic CrO2

Spintronic device architectures consisting of ferromagnetic chromium oxide electrodes in single-walled carbon nanotubes field effect transistor (SWCNT-FET) configuration have been fabricated to act as strategic building blocks for next generation super-compact high-speed nanoelectronic devices for logic and memory operations. Stable thin films of chromium oxides consisting of half-metallic ferromagnetic chromium-di-oxide (CrO2) were pulsed laser deposited (PLD) over lattice-matched rutile-type-tetragonal intermediate TiO2 thin layers over thermally oxidized Si substrates for engineering of the spintronic device structure. Focused ion beam (FIB) milling was applied to the ferromagnetic chromium oxide thin films for patterning of the source (S) and (D) electrodes. Typical electrical characteristics derived by lnρ vs. T−1/2 plots confirmed spin-dependent transport (SDT) as the dominant mechanism of electrical conduction upto temperatures of ∼280 K along with negative magnetoresistance (MR) of ∼30 % at 278 K. Electrical characteristics (output and transfer) of the spintronic device structure were drawn under application of magnetic field (H) in out-of-plane geometry at the temperatures of 5.6 K, 250 K & 300 K. Drain current (Id) is demonstrated to be controlled effectively as a function of gate bias (Vg) for different fixed Vd-biases at all the device operating temperatures. Change in %MR as a function of gate voltage (Vg) was acquired at T = 250 &T = 300 K that displayed higher %MR change under out-of-plane geometry of applied field of 0.75 T of the spintronic device operation.

Correlation Measurements for Carbon Nanotubes with Quantum Defects.

Single-photon sources are essential building blocks for the development of photonic quantum technology. Regarding potential practical application, an on-demand electrically driven quantum-light emitter on a chip is notably crucial for photonic integrated circuits. Here, we propose functionalized single-walled carbon nanotube field-effect transistors as a promising solid-state quantum-light source by demonstrating photon antibunching behavior via electrical excitation. The sp3 quantum defects were formed on the surface of (7, 5) carbon nanotubes by 3,5-dichlorophenyl functionalization, and individual carbon nanotubes were wired to graphene electrode pairs. Filtered electroluminescent defect-state emission at 77 K was coupled into a Hanbury Brown and Twiss experiment setup, and single-photon emission was observed by performing second-order correlation function measurements. We discuss the dependence of the intensity correlation measurement on electrical power and emission wavelength, highlighting the challenges of performing such measurements while simultaneously analyzing acquired data. Our results indicate a route toward room-temperature electrically triggered single-photon emission.

Orientation-Guided Immobilization of Probe DNA on swCNT-FET for Enhancing Sensitivity of EcoRV Detection.

We present a novel approach that integrates electrical measurements with molecular dynamics (MD) simulations to assess the activity of type-II restriction endonucleases, specifically EcoRV. Our approach employs a single-walled carbon nanotube field-effect transistor (swCNT-FET) functionalized with the EcoRV substrate DNA, enabling the detection of enzymatic cleavage events. Notably, we leveraged the methylene blue (MB) tag as an "orientation guide" to immobilize the EcoRV substrate DNA in a specific direction, thereby enhancing the proximity of the DNA cleavage reaction to the swCNT surface and consequently improving the sensitivity in EcoRV detection. We conducted computational modeling to compare the conformations and electrostatic potential (ESP) of MB-tagged DNA with its MB-free counterpart, providing strong support for our electrical measurements. Both conformational and ESP simulations exhibited robust agreement with our experimental data. The inhibitory efficacy of the EcoRV inhibitor aurintricarboxylic acid (ATA) was also evaluated, and the selectivity of the sensing device was examined.

Aramid Nanodielectrics for Ultraconformal Transparent Electronic Skins.

On-skin electronics require minimal thicknesses and decent transparency for conformal contact, imperceptible wearing, and visual aesthetics. It is challenging to search for advanced ultrathin dielectrics capable of supporting the active components while maintaining bending softness, easy handling, and wafer-scale processability. Here, self-delaminated aramid nanodielectrics (ANDs) are demonstrated, enabling any skin-like electronics easily exfoliated from the processing substrates after complicated nanofabrication. In addition, ANDs are mechanically strong, chemically and thermally stable, transparent and breathable, therefore are ideal substrates for soft electronics. As demonstrated, compliant epidermal electrodes comprising silver nanowires and ANDs can successfully record high-quality electromyogram signals with low motion artifacts and satisfying sweat and water resistance. Furthermore, ANDs can serve as both substrates and dielectrics in single-walled carbon nanotube field-effect transistors (FETs) with a merely 160-nm thickness, which can be operated within 4V with on/off ratios of 1.4 ± 0.5 × 105 , mobilities of 39.9 ± 2.2 cm2 V-1 s-1 , and negligible hysteresis. The ultraconformal FETs can function properly when wrapped around human hair without any degradation in performance.

Affordable paper-based SWNTs field-effect transistor biosensors for nucleic acid amplification-free and label-free detection of micro RNAs

Micro RNAs (miRNAs) are 19–23 nucleotides-long non-coding RNA which have been identified as important biomarkers for many diseases, including cancers. Here, we report an ultrasensitive, highly specific, label-free, and without nucleic acid amplification (NAA) detection of miRNAs using paper-based single-walled carbon nanotubes (SWNTs) field-effect transistor (FET) biosensors. The strategy involved a two-step protocol starting with direct hybridization of the target miRNA with a specific RNA probe immobilized on SWNTs networks deposited on the paper substrate to generate the first response, followed by the recognition of the resulting RNA/miRNA duplexes with the Carnation Italian ringspot virus p19 protein (p19) in a size-dependent manner, giving the second electrical response that magnified the biosensor sensitivity. As a demonstration, we detected the miRNA-122a, a promising biomarker for the diagnosis of early-stage hepatocellular carcinoma (HCC) in various sample matrices, including phosphate buffers, human serum, and synthetic saliva. We achieved the lowest detection of 0.1 aM and a wide dynamic range of 0.1 aM–1 fM, that demonstrated its potential for rapid, facile, low-cost, and point-of-care detection of miRNAs for early cancer diagnosis.

Heavy Ion Displacement Damage Effect in Carbon Nanotube Field Effect Transistors

Recent advances in carbon nanotube (CNT)-based integrated circuits have shown their potential in deep space exploration. In this work, the mechanism governing the heavy-ion-induced displacement damage (DD) effect in semiconducting single-walled CNT field effect transistors (FETs), which is one of the factors limiting device robustness in space, was first and thoroughly investigated. CNT FETs irradiated by a Xe ion fluence of 1012 ions/cm2 can maintain a high on/off current ratio, while transistors' performance failure is observed as the ion fluence increased to 5 × 1012 ions/cm2. Controllable experiments combined with numerical simulations revealed that the degradation mechanism changed as the nonionizing radiation energy built up. The trap generation in the gate dielectric, instead of the CNT channel, was identified as the dominating factor for the high-energy-radiation-induced device failure. Therefore, CNT FETs exhibited a >10× higher DD tolerance than that of Si devices, which was limited by the channel damage under irradiation. More importantly, the distinct failure mechanism determined that CNT FETs can maintain a high DD tolerance of 2.8 × 1013 MeV/g as the technology node scales down to 45 nm node, suggesting the potential of CNT-based VLSI for high-performance and high-robustness space applications.

Improving the linearity of synaptic plasticity of single-walled carbon nanotube field-effect transistors via CdSe quantum dots decoration

The linearity of synaptic plasticity of single-walled carbon nanotube field-effect transistor (SWCNT FET) was improved by CdSe quantum dots decoration. The linearity of synaptic plasticity in SWCNT FET with decorating QDs was further improved by reducing the P-type doping level from the atmosphere. The synaptic behavior of SWCNT FET is found to be dominated by the charging and discharging processes of interface traps and surface traps, which are predominantly composed of H2O/O2 redox couples. The improved synaptic behavior is mainly due to the reduction of the interface trap charging process after QDs decoration. The inherent correlation between the device synaptic behavior and the electron capture process of the traps are investigated through charging-based trap characterization. This study provides an effective scheme for improving linearity and designing new-type SWCNT synaptic devices.

High-performance carbon nanotube field-effect transistors with electron mobility of 39.4 cm2V−1s−1 using anion–π interaction doping

Single-walled carbon nanotube (SWNT) is desirable next generation semiconductor for flexible, transparent and even stretchable with exceptional electrical characteristics. Here, high-performance n-type semiconducting SWNT field-effect transistors (s-SWNT-FETs) are achieved by chemical doping using anion-π interaction between SWNT and anion of tetrabutylammonium fluoride (TBAF) salt. The Fermi level (EF) of SWNT shifts to the conduction band edge with increasing dopant concentration. The doped s-SWNT-FETs exhibit significant improvement in electron mobility (39.4 cm2V−1s−1) with high current on/off ratio (>104) compared to those of un-doped device. The doping using anion–π interaction leads to populate electron density of channel and reduces both channel and contact resistance by 99.0% and 99.6%. Excess carriers introduced by the doping compensate traps by shifting the EF toward conduction band edge. The doped device showed improved current stability after 10 h of bias stress test, while the current of undoped FET decreased by 40.4%. Finally, flexible FETs with TBAF doped s-SWNT network are demonstrated on polyethylene naphthalate substrate and show stable operation after 2000 times bending test.

Characteristic Control of SWCNT-FET by Varying Its Chirality and Dimensions

Carbon nanotube (CNT) has witnessed great importance due to its electronic and mechanical properties. The CNTFET was designed to provide high-performance electronic devices. Therefore, the carbon nanotube is representing a potential material for future microelectronic devices. In this paper, COMSOL Multiphysics was used to design and a simulate single-walled carbon nanotube field-effect transistor with a back gate. The insulation layer used in the model was silicon dioxide. The influence of changing its thickness on the drain current was discussed. In addition, the specification of carbon nanotubes was investigated in terms of changing their diameter and length. Moreover, this paper reveals the current transport of CNTFET for different applied gate voltage and drain voltage. In our work, the CNTFET behaves as n-type FET with transconductance g m ≈1.25uA and electron mobility equal to 4.77×10-26cm2v-1s-1. To obtain semiconducting properties for the CNT material, it must consider the chirality when altering the carbon nanotubes diameter. In the proposed device, the diameter values range from 1nm to 4.5nm. It was found that increasing the diameter range resulted in decreasing bandgap from 0.497 eV to 0.110 eV and increasing drain current from 4.075 uA to 31.33 uA.

The Effect of Charge Traps on Leakage Current in Sensitive Nano-Sensors Based on Single-Walled Carbon Nanotube Field-Effect Transistors (SWCNT-FET)

The Effect of Charge Traps on Leakage Current in Sensitive Nano-Sensors Based on Single-Walled Carbon Nanotube Field-Effect Transistors (SWCNT-FET)

Cerebrospinal Fluid Leak Detection with a Carbon Nanotube-Based Field-Effect Transistor Biosensing Platform.

Cerebrospinal fluid (CSF) leakage may lead to life-threatening complications if not detected promptly. However, gel electrophoresis, the gold-standard test for confirming CSF leakage by detecting beta2-transferrin (β2-Tf), requires 3-6 h and is labor-intensive. We developed a new β2-Tf detection platform for rapid identification of CSF leakage. The three-step design, which includes two steps of affinity chromatography and a rapid sensing step using a semiconductor-enriched single-walled carbon nanotube field-effect transistor (FET) sensor, circumvented the lack of selectivity that antitransferrin antibody exhibits for transferrin isoforms and markedly shortened the detection time. Furthermore, three different sensing configurations for the FET sensor were investigated for obtaining the optimal β2-Tf sensing results. Finally, body fluid (CSF and serum) tests employing our three-step strategy demonstrated high sensitivity, suggesting its potential to be used as a rapid diagnostic tool for CSF leakage.

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.

Radiation-hardened property of single-walled carbon nanotube film-based field-effect transistors under low-energy proton irradiation

Strong C–C bonds, nanoscale cross-section and low atomic number make single-walled carbon nanotubes (SWCNTs) a potential candidate material for integrated circuits (ICs) applied in outer space. However, very little work combines the simulation calculations with the electrical measurements of SWCNT field-effect transistors (FETs), which limits further understanding on the mechanisms of radiation effects. Here, SWCNT film-based FETs were fabricated to explore the total ionizing dose (TID) and displacement damage effect on the electrical performance under low-energy proton irradiation with different fluences up to 1 × 1015 p/cm2. Large negative shift of the threshold voltage and obvious decrease of the on-state current verified the TID effect caused in the oxide layer. The stability of the subthreshold swing and the off-state current reveals that the displacement damage caused in the CNT layer is not serious, which proves that the CNT film is radiation-hardened. Specially, according to the simulation, we found the displacement damage caused by protons is different in the source/drain contact area and channel area, leading to varying degrees of change for the contact resistance and sheet resistance. Having analyzed the simulation results and electrical measurements, we explained the low-energy proton irradiation mechanism of the CNT FETs, which is essential for the construction of radiation-hardened CNT film-based ICs for aircrafts.

Improving threshold voltage and on/off current ratio of single-walled carbon nanotube field-effect transistor by post-sonication treatments

In the process of solution-based fabrication of Single-walled Carbon Nanotube Field Effect Transistor (SWCNT FET), the quality of SWCNTs network plays an important role. SWCNTs networks have disorders and defects because of chirality mismatches that cause the weaker tunneling between SWCNTs, hence suppressing conductance and the electrical performance of the device. In this paper, we present a study on the impact of SWCNTs network structure, which were formed in the channel on the prefabricated test chips, on electrical characteristic parameters like threshold voltage (VT) and on/off current ratio (ION/IOFF). Also, we propose a simple and low-cost post-process to decrease the VT and enhance ION/IOFF of SWCNT FET comparable to the reasonably good performances of the same devices to the date. Post-sonication treatments of the devices in the deionized water and the isopropyl alcohol not only removed the residual impurities remained between individual SWCNTs and around their surface and substrate, but also decreased the structural defects of their network (based on the provided Raman spectroscopy results). This improves ION/IOFF up to 153 times and shifts VT in the negative direction up to almost 0 V. The results indicate the importance of the improvement of SWCNTs network structure in enhancing SWCNT FET electrical performance.

Rapid Detection of SARS-CoV-2 Antigens Using High-Purity Semiconducting Single-Walled Carbon Nanotube-Based Field-Effect Transistors.

Early diagnosis of SARS-CoV-2 infection is critical for facilitating proper containment procedures, and a rapid, sensitive antigen assay is a critical step in curbing the pandemic. In this work, we report the use of a high-purity semiconducting (sc) single-walled carbon nanotube (SWCNT)-based field-effect transistor (FET) decorated with specific binding chemistry to assess the presence of SARS-CoV-2 antigens in clinical nasopharyngeal samples. Our SWCNT FET sensors, with functionalization of the anti-SARS-CoV-2 spike protein antibody (SAb) and anti-nucleocapsid protein antibody, detected the S antigen (SAg) and N antigen (NAg), reaching a limit of detection of 0.55 fg/mL for SAg and 0.016 fg/mL for NAg in calibration samples. SAb-functionalized FET sensors also exhibited good sensing performance in discriminating positive and negative clinical samples, indicating a proof of principle for use as a rapid COVID-19 antigen diagnostic tool with high analytical sensitivity and specificity at low cost.

Photosensitive Complementary Inverters Composed of n‐Channel ReS2 and p‐Channel Single‐Walled Carbon Nanotube Field‐Effect Transistors

For robustness on security and ultralow power consumption for Internet of Things (IoT) sensors, including ultraminiaturization for high chip density, 2D multilayered ReS2 field‐effect transistors (FETs) combined with photoinsensitive single‐walled carbon nanotube (SWNT) FETs are demonstrated for application in light‐to‐frequency (LTF) conversion circuits. Herein, multilayered ReS2 FETs with a direct bandgap (≈1.5 eV) have discernible photoresponsivity of ≈17 A W−1 for red and ≈128 A W−1 for green, respectively, with photodetectivity (≈109 Jones), leading to excellent operation for photosensitive inverters, partly associated with the photoinsensitive SWNT FETs for p‐channel devices. Moreover, the electrical parameters for photosensitive complementary inverters, according to different wavelengths in the dark and under, red (λR = 660 nm), green (λG = 530 nm), and blue (λB = 450 nm) light, are experimentally extracted, and their SPICE simulation‐based validation on working principles of ring oscillators (ROs) is confirmed under light illumination. More impressively, ultralow power consumption for the proposed scheme is achieved due to both the direct bandgap and the large‐energy bandgap, as compared with conventional multilayered MoS2 FET‐based photosensitive inverters, rationally validating the promising opportunity for applications in the envisioned IoT sensor systems.

Study of uniformly doped nano scale single-walled CNTFET under dark and illuminated conditions

Advancement in technology has resulted in transistors scaling down to nanometers. The evolution has resulted in investigations which extend to the structure of nanometer devices and the theories related to them. The extent of the investigation has stepped into Single-walled carbon nanotube field effect transistor (SW-CNTFET). The numerical method of self-consistent 3D Poisson and Schrödinger equations is solved by the Leibmann's iteration method. Further, study the effect of illumination on different parameters including the surface potential, drain current, mobility, transconductance and sub-threshold of n-type SW- CNTFET with high-k gate dielectric constant. Finding is that the use of Hfo2 high-k dielectric enhances the device characteristics. Comparing the drain current in illumination and dark condition, there is a notable increase when illuminated. The simulated results of proposed CNTFET photo detector were compared with existing MOSFET photo detector. Better drain current, transconductance and cut off frequency were obtained for the CNTFET. This result is in very much agreement with results obtained from numerical simulations. These findings on optical properties of carbon nanotubes (CNTFET) are sure to advance the fields of photo detectors, OEIC, solar cells and IC fabrications.