Single-walled Carbon Nanotube Devices Research Articles

Stable photothermal conversion in single-walled carbon nanotube device with pn-junction under uniform sunlight irradiation

N-type single-walled carbon nanotube (SWCNT) films with high air stabilities have attracted significant attention for their potential application in SWCNT devices featuring pn-junctions for power generation. However, SWCNT devices must be locally heated or formed into suspended structures to generate a temperature difference and produce output power. In this study, pn-junction SWCNT films were fabricated via vacuum filtration and subsequently attached to a polyimide substrate, enabling the creation of SWCNT devices without the need for suspended structures. Upon uniform irradiation with artificial sunlight, the SWCNT device produced a stable output voltage and short-circuit photocurrent. A thermographic image showed the emergence of a temperature gradient originating from the center of the SWCNT film and extending to the edge of the polyimide substrate. This phenomenon can be attributed to the higher optical absorption of SWCNT films compared to that of polyimide substrates. Consequently, the diffusion of carriers within the device generated an electric potential difference. Therefore, the SWCNT device generated a temperature gradient and yielded output power under uniform sunlight irradiation. These findings may aid in the development of facile and flexible optical devices, including photodetectors and hybrid devices integrating solar cells.

Infrared Light-Emitting Diodes Based on Chirality-Sorted Carbon Nanotube Films.

An important goal in carbon nanotube optoelectronics is to achieve a high-performance near-infrared light source. But there are still many challenges such as the purity of single-walled carbon nanotube (SWCNT) chirality, nonradiative defects, thin-film quality, and device structure design. Here, we realize infrared light-emitting diodes (LEDs) based on chirality-sorted (10, 5) SWCNT network films, which operate at a low bias voltage and emit at a telecom O band of 1290 nm. Asymmetric palladium (Pd) and hafnium (Hf) contacts are used as electrodes for hole and electron injection, respectively. However, the large Schottky barrier at the interface of the SWCNTs and the Hf electrode, primarily resulting from the polymer wrapped on the nanotube surface during the sorting process, leads to inefficient electron injection and thus a low electroluminescence efficiency. We find that the efficiency of electron injection can be improved by the local doping of the nanotubes with dielectric layers of YOX-HfO2, which reduces the Schottky barrier at the SWCNT/Hf interface. Accordingly, the (10, 5) SWCNT film-based LED achieves an external quantum efficiency of larger than 0.05% without any optical coupling structure. With further improvement, we expect that such an infrared light source will have great application potential in the carbon nanotube monolithic optoelectronic integrated system and on-chip optical interconnection, especially in the field of short-distance optical fiber communications and data center.

Boosting thermoelectric performance of carbon nanotube-based materials and devices by radical-containing molecules

Organic thermoelectric materials are attracting growing research interests as they are seen as environmentally friendly functional materials with tremendous potential for use in waste heat recovery. The absence of low electrical conductivity has somewhat slowed down the development of most organic thermoelectric materials. Blending the organic semiconductor materials with single walled carbon nanotube (SWCNT) has become an extremely important strategy to boost the conductivity and thermoelectric performance of organic materials. Therefore, in this paper, novel arylimide compounds NDI-2 T and PDI-2 T with radical substituents of TEMPO are designed from molecular engineering, complexing with SWCNT as organic thermoelectric composites. Compared with the non-radical compounds of NDI-2TP and PDI-2TP, the introduction of radicals in NDI-2 T and PDI-2 T can significantly improve the performance of the thermoelectric composites. Radical-containing composite films exhibit outstanding thermoelectric performance compared to the film based on non-radical molecules. The best power factor reaching 278.2 ± 8.2 μW m−1 K−2 for p-type films, while n-type films can attain 64.6 ± 13.5 μW m−1 K−2. The NDI-2 T/SWCNT devices can obtain a maximum output power of 0.94 μW when the temperature gradient is around 60 K, which is 5 times higher of NDI-2TP/SWCNT device. The significantly enhanced thermoelectric performance of the composite film based on organic radical compounds is resulted from the increased interactions between the radical compounds and SWCNTs and modulated carrier concentrations in the composite films. This work provides a new direction for the design of high-performance thermoelectric materials and devices.

TCO-free perovskite solar cells in taking advantage of SWCNT/TiO2 core/shell sponge

A nanohybrid of titanium dioxide (TiO 2 ) and single-walled carbon nanotubes (SWCNTs) with dual functions of collecting electrons and transparent electrode layer is synthesized by nano-cluster deposition technology. The super-hollow structure of the SWCNTs was directly fabricated via arc discharge and fully covered with a thin layer (∼15 nm) of TiO 2 , which formed the SWCNT/TiO 2 core/shell sponge. The developed SWCNT/TiO 2 core/shell sponge is used directly as scaffolding for a light absorber and electron collector in transparent conducting oxide (TCO) electrode-free perovskite solar cells (PSCs) for the first time, which exhibited a power conversion efficiency of 7.2%. The large surface area of the core/shell bundle is sufficiently effective in transferring the photogenerated electron from the Perovskite absorber to the SWCNTs. More importantly, the findings of this work could support the concept of replacing the conventional TCO in PSCs and pave the way to further work for developing inexpensive and flexible PSCs. • Replacing conventional transparent conducting oxide electrode with carbon nanotube in perovskite solar cell. • Dual functions of SWCNT/TiO 2 core/shell sponge as electron collector and scaffold for light absorber. • The photovoltaic performance of SWCNT and FTO-based devices was shown in comparative investigation. • The use of high quality SWCNT/TiO 2 sponge was believed in further development of low-cost PSC.

PCB mounted sensor with high sensitivity SWNT-Based devices for gas sensing applications

In this paper, the fabrication of aligned semiconducting single-walled carbon nanotube (SWNT) devices on a thermally grown silicon dioxide (SiO2) over silicon (Si) substrate is presented. The SWNTs are aligned between the nickel fingers that are patterned on the substrate. Subsequently, the fabricated devices are bonded onto a low-cost printed circuit board (PCB) with wire bonder. The mounted sensors have been tested for carbon dioxide (CO2) gas, acetone, and isopropyl alcohol (IPA) vapor sensing at room temperature. The sensitivity values of 27% for the concentration of 15000 ​ppm of CO2, 52% for the concentration of 7000 ​ppm of acetone, and 67% for the concentration of 900 ​ppm of IPA have been observed with good response and recovery times. The fabricated sensors show better performance than the already reported sensors.

LED Device Based on Single-Walled Carbon Nanotube Arrays

The migration model of the (n, 0) zigzag SWNT is established on the basis of Mathiessen’s law to calculate carrier mobility, which are the foundation for performance analysis of electroluminescence light emission. The split-gate technique is used to create p-and n-doped regions in the single-walled carbon nanotube (SWNT) arrays that are separated by a gap with a width of several microns. The LED devices based on SWNT arrays using split-gate technique are fabricated and tested by using an optical measurement system. Compared to the LED with the central gate, the split-gate SWNT LED has enhanced the light generation efficiency of the intrinsic SWNT array segment by decreasing the potential barrier across the junction of the intrinsic SWNT array segment. The results demonstrate the luminescent principle of LED based on SWNT array in theoretical simulation and device measurement.

Directed assembly of multiplexed single chirality carbon nanotube devices

Herein, we present the fabrication of multiplexed single-walled carbon nanotube (SWCNT) devices, where selected chiralities were separately immobilized on one chip with single-tube precision. Each chirality was subsequently electrically measured individually. Specifically, (6,5) and (7,5) SWCNT species were isolated via aqueous two-phase polymer systems, after which dielectrophoresis was used to precisely control the placement of each chirality, along with a metallic species, separately on prepatterned electrodes on a single chip.

Silicon Shadow Mask Technology for Aligning and In Situ Sorting of Semiconducting SWNTs for Sensitivity Enhancement: A Case Study of NO2 Gas Sensor.

Single-walled carbon nanotubes (SWNTs) are incorporated in different device configurations such as chemiresistors and field-effect transistors (FETs) as a sensing element for the fabrication of highly sensitive and specific biochemical sensors. For this purpose, sorting and aligning of semiconducting SWNTs between the electrodes is advantageous. In this work, a silicon shadow mask fabricated using conventional semiconductor processes and silicon bulk micromachining was used to make metal contacts over SWNTs with a minimum feature of 1 μm gap between the electrodes. The developed silicon shadow mask-based metal contact patterning process is cost-effective and free from photoresist (PR) chemical coatings and thermal processing. After a detailed investigation, sodium dodecyl sulfate (SDS), an anionic surfactant, along with ultrasonication process, was found to be effective for the removal of unclamped and metallic SWNTs, resulting in aligned and clamped semiconducting SWNTs between the electrodes. The presence of aligned semiconducting SWNTs was confirmed using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy techniques. The fabricated devices were tested for nitrogen dioxide (NO2) gas sensing as a test case. The sensitivity enhancement of ∼21 to 76% in the 20-80 ppm NO2 concentration range has been observed in the case of aligned semiconducting SWNT devices compared to the random network SWNT-based sensors.

Detection of chirality of single-walled carbon nanotubes on hexagonal boron nitride

Single-walled carbon nanotube (SWNT) has attracted widespread attention for its unique one-dimensional atomic structure and outstanding physical and chemical properties. For both fundamental research and practical applications, it is critical to figure out the chirality of SWNT because the electronic band structure and the consequent electrical and optical properties are determined by its chirality. Here, we found that the chirality of SWNT on an insulating hexagonal boron nitride (h-BN) substrate can be obtained in a quick and concise manner through measuring the aligning direction and the diameter of SWNT. Additionally, Rayleigh scattering spectroscopy is conducted to confirm the obtained chirality. The developed technique for direct detection of chirality of SWNT on an insulating h-BN substrate could advance the study of chirality-dependent functional SWNT devices and the applications of SWNT related to chirality.

(Invited) Single-Molecule Electronics for DNA Sequencing

Nanoscale materials provide new opportunities to interface solid-state electronics with biomolecules and biochemical activity. For example, single-walled carbon nanotubes (SWNTs) have the special property of electronic resistance that is sensitive to single electrons. We have exploited this sensitivity to build nanoelectronic biosensors that monitor the biochemical activity of individual proteins [1]. As an attached protein moves, binds, or performs catalysis, its charged amino acid sidechains induce resistance fluctuations in the SWNT device that may be monitored with microsecond resolution [2].Recently, we have used this measurement platform for single-molecule measurements of DNA polymerases [3]. Polymerases are the key enzymes for converting single-stranded DNA to double-stranded helices, the primary step in DNA replication, amplification, and most sequencing technologies. When a polymerase processing DNA is also attached to a SWNT device, the electrical signal provides a high-resolution readout of single-nucleotide incorporations and exciting possibilities for high-density, high-throughput electronic DNA sequencing.To investigate the feasibility of electronic DNA sequencing, we have compared single-molecule transduction by DNA polymerases from three different organisms. By working with multiple families of DNA polymerases, we have tested the applicability of the electronic technique while also generating detailed records of differences among the enzymes. For example, we observe an anomalous rate variability when measuring the polymerase from the bacillus phage φ29. Base incorporation rates average 20 s-1 for most the enzymes processing single-stranded DNA templates, but rates up to 200 and 400 s-1 occurred when φ29 encountered homopolymeric sequences of poly(dT) or poly(dC), respectively. When processing poly(dA) and poly(dG) sequences, on the other hand, φ29 had bursts of activity interrupted by pauses lasting 50 to 300 s. This sequence-dependent activity illustrates one way that single-molecule methods reveal information hidden in ensemble-based techniques.Another workhorse protein in DNA sequencing technologies is the DNA polymerase derived from the thermophilic bacteria Thermus aquaticus (Taq). Anomalous stability at high temperatures makes Taq a unique enzyme for the polymerase chain reaction (PCR) and commercial amplification of DNA. In a first for single-molecule biophysics, SWNT devices have recorded Taq activity over a wide temperature range from 22 to 94 °C, including the typical PCR operating temperature of 72 °C. Even operating at this high temperature, the technique resolved Taq testing incoming nucleotides for complementarity and incorporating correct matches in the base-by-base construction of Watson-Crick pairs. The detailed recordings reveal the similarities of Taq’s operation to other, room temperature polymerases.[1] Y. Choi, et. al., Science 335, 319 (2012). [2] M. V. Akhterov, et. al., ACS Chem. Biol. 10, 1495 (2015). [3] T. J. Olsen et. al., JACS 135, 7855 (2013); O. T. Gul et. al., Biosensors 6, 29 (2016)

(Invited) Controlling Carbon Nanotubes By DNA: From Separation to Integration

A unique feature of single-wall carbon nanotube (SWCNT) material is its structure diversity: within the same rolled-up graphene sheet structure framework one finds SWCNTs of different electronic bandgaps: metals with zero bandgap, quasi-metals with meV bandgap and semiconductors with ~ 1 eV bandgap. However, making use of SWCNT structure diversity requires a method to obtain SWCNTs of defined structures. In this contribution, we present our current state of DNA-based sorting of SWCNTs. In particular, we show our ability to put any DNA sequence on any SWCNT species, enabling DNA-based assembly of high-density SWCNT devices. In the end, we discuss the design of a device we call Photon Perceptron Array (PPA). PPA is an array of micron-sized spectrometer units that can measure the spectrum of incoming photon in the wavelength range of 200 nm to 2000 nm (and possibly going all the way to THz), with a spatial resolution comparable to the size of a single spectrometer unit. Each spectrometer unit is composed of a set of distinct photodetectors made of SWCNTs of defined atomic structures, placed in parallel with tube-to-tube separations controlled at nanometer precision by DNA origami technology. A high-density array of identical spectrometers can be constructed by placing DNA origami/carbon nanotube complexes in photolithographically-defined locations. PPA may be used for spectral imaging in many fields of science and technology.

An Electrically Actuated, Carbon-Nanotube-Based Biomimetic Ion Pump.

Single-walled carbon nanotubes (SWCNTs) are well-established transporters of electronic current, electrolyte, and ions. In this work, we demonstrate an electrically actuated biomimetic ion pump by combining these electronic and nanofluidic transport capabilities within an individual SWCNT device. Ion pumping is driven by a solid-state electronic input, as Coulomb drag coupling transduces electrical energy from solid-state charge along the SWCNT shell to electrolyte inside the SWCNT core. Short-circuit ionic currents, measured without an electrolyte potential difference, exceed 1 nA and scale larger with increasing ion concentrations through 1 M, demonstrating applicability under physiological (∼140 mM) and saltwater (∼600 mM) conditions. The interlayer coupling allows ionic currents to be tuned with the source-drain potential difference and electronic currents to be tuned with the electrolyte potential difference. This combined electronic-nanofluidic SWCNT device presents intriguing applications as a biomimetic ion pump or component of an artificial membrane.

(Invited) Design of Metal - Carbon Nanotube Structures for Electronic and Optoelectronic Applications

Interconnecting graphitic surfaces has generated significant interest especially in electronics and optoelectronics motivated by the multi-functionality of the novel carbon structures. Bridging the π-conjugated carbon surfaces of single-walled carbon nanotubes (SWNTs) have special implications in next-generation electronics. We discuss the electrical transport properties of aligned semiconducting SWCNT films and the effect of metal atoms on the film conductivities. Deposition of transition metal and alkali metal atoms on aligned SWNTs increases the film conductivities via distinctly different mechanisms. Hexahapto metal-bridged aligned SWNTs can be engineered as reversible optoelectronic switches. We demonstrate aligned SWNT devices that are reversibly switched between a state of high electrical conductivity (on) by light and low electrical conductivity (off) by applied potential.

Gate-enhanced photocurrent of (6,5) single-walled carbon nanotube based field effect transistor

A visible sensing field effect transistor (FET) with a channel length of 100 nm for individual (6,5) single-walled carbon nanotubes (SWCNTs) is fabricated via a selective sorting method using 9,9-dioctyfluorenyl-2,7-diyl–bipyridine (PFO–BPy) polymer. The FET of the (6,5) SWCNTs shows p-type behavior with hundreds of on-off ratios and on-state conductivity of 50 ± 4.0 (Ω m)−1. In addition, the photocurrent of the FET of the (6,5) SWCNTs in the visible range increases (maximum 200 times at 620 nm) with higher gate voltage. E22 transition and PFO-BPy transition are observed in the FET of the (6,5) SWCNTs without application of a gate voltage. Interestingly, exciton-phonon coupled E22 transition due to gate-doping (p-type), which has been reported in photoluminescence and absorption studies, is expected to occur in the photocurrent of the FET at negatively higher gate voltage (≤−4 V). In addition, the exciton-phonon coupled E22 transition is prominently observable when carrier concentration by gate doping becomes approximately two-hundred sixty times (260 ± 43) larger than carrier concentration without application of a gate voltage. This demonstration would be useful for the development of SWCNT-based visible sensors with gate control in the SWCNT devices.

Oligomer Hydrate Crystallization Improves Carbon Nanotube Memory

Single-walled carbon nanotube (SWCNT) field-effect transistor (FET) devices have potential for memory storage applications. Devices fabricated with semiconducting SWCNT ink using dielectrophoresis were coated with a renewably sourced poly(oxacyclobutane) oligomer. It was found that this oligomer crystallizes with water to form a semicrystalline oligomer hydrate material. Crystallization also occurs on the SWCNT device surface in ambient conditions, resulting in dramatically increased hysteresis of the SWCNT-FET I-Vg curves. Using alternating current impedance measurements, we found that the oligomer hydrate crystals store charge, acting as a capacitor encapsulating the nanotube network. This capacitive material can serve to electrostatically gate the SWCNT network. The charge storage properties of the oligomer hydrate crystals were applied to store “0” and “1” bits separated by ∼4 orders of magnitude of current. Utilizing powder X-ray diffraction and simulation, we have demonstrated that this semicrystall...

Large positive magnetoresistance in semiconducting single-walled carbon nanotubes at room temperature.

We have investigated the effect of a magnetic field on the resistance (magnetoresistance, MR) of single-walled carbon nanotube (SWNT) arrays. The SWNT devices consist of a mixture of metallic and semiconducting SWNTs between palladium electrodes. The MR of the devices is studied at room temperature and in the presence of perpendicular magnetic fields up to 0.24 tesla. The resistance increases as the external magnetic field becomes higher, suggesting a positive MR of SWNTs. After etching the metallic SWNTs by electrical breakdown, the MR can be further enhanced. Large positive MR values about 15%, 20% and 25% were found in three different devices at 0.24 tesla for semiconducting SWNTs at room temperature. Our results show potential for the development of magneto-electronic devices that are operable at room temperature.

Nanogap-Engineerable Electromechanical System for Ultralow Power Memory.

Nanogap engineering of low‐dimensional nanomaterials has received considerable interest in a variety of fields, ranging from molecular electronics to memories. Creating nanogaps at a certain position is of vital importance for the repeatable fabrication of the devices. Here, a rational design of nonvolatile memories based on sub‐5 nm nanogaped single‐walled carbon nanotubes (SWNTs) via the electromechanical motion is reported. The nanogaps are readily realized by electroburning in a partially suspended SWNT device with nanoscale region. The SWNT memory devices are applicable for both metallic and semiconducting SWNTs, resolving the challenge of separation of semiconducting SWNTs from metallic ones. Meanwhile, the memory devices exhibit excellent performance: ultralow writing energy (4.1 × 10−19 J bit−1), ON/OFF ratio of 105, stable switching ON operations, and over 30 h retention time in ambient conditions.

Controlling conducting channels of single-walled carbon nanotube array with atomic force microscopy

In this paper, we report a technique of controlling the number of single-walled carbon nanotubes (SWNTs) between two electrodes. The SWNT devices consist of an array of SWNTs between two silver/palladium electrodes, which are fabricated with electron beam lithography and silver. Using the tip-sample interaction in contact mode of atomic force microscopy (AFM), the number of individual SWNTs can be controllably decreased. The current–voltage measurements indicate that the resistance increases when the conducting channels of SWNTs are reduced. This simple and controllable approach could be useful for the assembly of high performance devices with a desired number of channels for future electronic investigations.

Single walled carbon nanotube-based stochastic resonance device with molecular self-noise source

Stochastic resonance (SR) is an intrinsic noise usage system for small-signal sensing found in various living creatures. The noise-enhanced signal transmission and detection system, which is probabilistic but consumes low power, has not been used in modern electronics. We demonstrated SR in a summing network based on a single-walled carbon nanotube (SWNT) device that detects small subthreshold signals with very low current flow. The nonlinear current-voltage characteristics of this SWNT device, which incorporated Cr electrodes, were used as the threshold level of signal detection. The adsorption of redox-active polyoxometalate molecules on SWNTs generated additional noise, which was utilized as a self-noise source. To form a summing network SR device, a large number of SWNTs were aligned parallel to each other between the electrodes, which increased the signal detection ability. The functional capabilities of the present small-size summing network SR device, which rely on dense nanomaterials and exploit intrinsic spontaneous noise at room temperature, offer a glimpse of future bio-inspired electronic devices.

Environmental Impacts from Photovoltaic Solar Cells Made with Single Walled Carbon Nanotubes.

An ex-ante life cycle inventory was developed for single walled carbon nanotube (SWCNT) PV cells, including a laboratory-made 1% efficient device and an aspirational 28% efficient four-cell tandem device. The environmental impact of unit energy generation from the mono-Si PV technology was used as a reference point. Compared to monocrystalline Si (mono-Si), the environmental impacts from 1% SWCNT was ∼18 times higher due mainly to the short lifetime of three years. However, even with the same short lifetime, the 28% cell had lower environmental impacts than mono-Si. The effects of lifetime and efficiency on the environmental impacts were further examined. This analysis showed that if the SWCNT device efficiency had the same value as the best efficiency of the material under comparison, to match the total normalized impacts of the mono- and poly-Si, CIGS, CdTe, and a-Si devices, the SWCNT devices would need a lifetime of 2.8, 3.5, 5.3, 5.1, and 10.8 years, respectively. It was also found that if the SWCNT PV has an efficiency of 4.5% or higher, its energy payback time would be lower than other existing and emerging PV technologies. The major impacts of SWCNT PV came from the cell's materials synthesis.