Flexible, Transparent Single-Walled Carbon Nanotube Transistors with Graphene Electrodes
Application: Transistors
Citation: Sukjae Jang, Houk Jang, Youngbin Lee, Daewoo Suh, Seunghyun Baik, Byung Hee Hong, Jong-Hyun Ahn, Nanotechnology (2010), 21 425201.
Summary: This paper reports a mechanically flexible, transparent thin film transistor that uses graphene as a conducting electrode and single-walled carbon nanotubes (SWNTs) as a semiconducting channel. These SWNTs and graphene films were printed on flexible plastic substrates using a printing method. The resulting devices exhibited a mobility of ~ 2 cm2 V -1 s -1, On/Off ratio of ~ 102, transmittance of ~ 81% and excellent mechanical bendability.
Quantifying the Electron Transfer Sites of Graphene
Application: Transistors
Citation: Philip M. Hallam, Craig E. Banks, Electrochemistry Communications (2010), 10.1016/j.elecom.2010.10.030.
Summary: We demonstrate that graphene modified electrodes do not suffer from thin layer effects which is commonly observed in carbon nanotube modified electrodes which precludes mechanistic information to be deduced and false claims of electro-catalysis to be inferred. A simple methodology is presented allowing the electron transfer sites of graphene, viz edge plane sites to be readily determined, allowing researchers to make comparisons in the graphene field such as electrochemical generation and storage devices where graphene has been beneficially applied. Interestingly we find that in comparison of graphene orientated on a surface with that of multi-walled carbon nanotubes, the latter has an identical % of electron transfer sites (edge plane content) with that of the former.
Ultrabroadband Photodetection Based on Graphene Ink
Application: Transistors
Citation: A. Radoi, A. Iordanescu, A. Cismaru, M. Dragoman, D. Dragoman, Nanotechnology (2010), 21 455202.
Summary: We report photodetection in a very large spectral bandwidth, which encompasses ultraviolet, visible and near infrared, using graphene inks or graphene inks functionalized with either gold or silver nanoparticles, or gold nanoparticles further encapsulated with bovine serum albumin deposited on interdigitated electrodes fabricated on a silicon dioxide/silicon substrate. In contrast to gold-functionalized graphene inks, which have responsivities better than 1 mA W-1 at a 0.1 V bias over the huge bandwidth extending from 215 to 2500 nm, Ag-functionalized inks show at least a four-fold increased responsivity, with a record value of 13.7 mA W-1 in near infrared.
Solvation Dynamics of Coumarin 153 in SDS Dispersed Single Walled Carbon Nanotubes (SWNTs)
Application: Transistors
Citation: Abhigyan Sengupta, Partha Hazra, Chemical Physics Letters (2010), 10.1016/j.cplett.2010.10.049.
Summary: We have studied the solvation dynamics and rotational relaxation of Coumarin 153 (C-153) in SDS dispersed two different types of single walled carbon nanotubes (SWNTs), namely metallic and semiconducting, using picosecond fluorescence spectroscopy. It has been observed that solvation dynamics of C-153 in SWNTs is severely retarded compared to pure water and SDS micelle. Time resolved fluorescence anisotropy study suggests that C-153 molecules are located on the surface of SWNT, where the rotational motion of the probe is severely hindered compared to SDS micelle due to the restriction imposed by SWNT surface as well as surrounding SDS monomers or SDS half-cylindrical micelles adsorbed on SWNT surface.
Macroelectronic Integrated Circuits Using High-Performance Separated Carbon Nanotube Thin-Film Transistors
Application: Transistors
Citation: Chuan Wang, Jialu Zhang, Chongwu Zhou, ACS Nano (2010), 4, 12, 7123–7132.
Summary: Macroelectronic integrated circuits are widely used in applications such as flat panel display and transparent electronics, as well as flexible and stretchable electronics. However, the challenge is to find the channel material that can simultaneously offer low temperature processing, high mobility, transparency, and flexibility. Here in this paper, we report the application of high-performance separated nanotube thin-film transistors for macroelectronic integrated circuits. We have systematically investigated the performance of thin- film transistors using separated nanotubes with 95% and 98% semiconducting nanotubes, and high mobility transistors have been achieved. In addition, we observed that while 95% semiconducting nanotubes are ideal for applications requiring high mobility (up to 67 cm2 V-1 s-1) such as analog and radio frequency applications, 98% semiconducting nanotubes are ideal for applications requiring high on/off ratios (>104 with channel length down to 4µm). Furthermore, integrated logic gates such as inverter, NAND, and NOR have been designed and demonstrated using 98% semiconducting nanotube devices with individual gating, and symmetric input/output behavior is achieved, which is crucial for the cascading of multiple stages of logic blocks and larger scale integration. Our approach can serve as the critical foundation for future nanotube-based thin-film macroelectronics.
Ultrasensitive Detection of DNA Molecules with High On/Off Single-Walled Carbon Nanotube Network
Application: Transistors
Citation: Dongliang Fu, Haruya Okimoto, Chun Wei Lee, Taishi Takenobu, Yoshihiro Iwasa, Hiromichi Kataura, Lain-Jong Li, Advanced Materials (2010), 10.1002/adma.201002305.
Summary: Semiconducting networks were found to be extremely sensitive to charges, which promises the electrical detection of ultralow concentrations of DNA (down to 0.1 fM, ∼100 DNA molecules).
Electronic-Structure-Dependent Bacterial Cytotoxicity of Single-Walled Carbon Nanotubes
Application: Transistors
Citation: Chad D. Vecitis, Katherine R. Zodrow, Seoktae Kang, Menachem Elimelech, ACS Nano (2010), 4, 9, 5471-5479.
Summary: Single-walled carbon nanotubes (SWNTs) have been previously observed to be strong antimicrobial agents, and SWNT coatings can significantly reduce biofilm formation. However, the SWNT antimicrobial mechanism is not fully understood. Previous studies on SWNT cytotoxicity have concluded that membrane stress (i.e., direct SWN--bacteria contact resulting in membrane perturbation and the release of intracellular contents) was the primary cause of cell death. Gene expression studies have indicated oxidative stress may be active, as well. Here, it is demonstrated for the first time how SWNT electronic structure (i.e., metallic versus semiconducting) is a key factor regulating SWNT antimicrobial activity. Experiments were performed with well-characterized SWNTs of similar length and diameter but varying fraction of metallic nanotubes. Loss of Escherichia coli viability was observed to increase with an increasing fraction of metallic SWNTs. Time-dependent cytotoxicity measurements indicated that in all cases the majority of the SWNT antimicrobial action occurs shortly after (<15 min) bacteria--SWNT contact. The SWNT toxicity mechanism was investigated by in vitro SWNT-mediated oxidation of glutathione, a common intracellular thiol that serves as an antioxidant and redox state mediator. The extent of glutathione oxidation was observed to increase with increasing fraction of metallic SWNTs, indicating an elevated role of oxidative stress. Scanning electron microscopy images of E. coli in contact with the SWNTs demonstrated electronic structure-dependent morphological changes consistent with cytotoxicity and glutathione oxidation results. A three-step SWNT antimicrobial mechanism is proposed involving (i) initial SWN--bacteria contact, (ii) perturbation of the cell membrane, and (iii) electronic structure-dependent bacterial oxidation.
Characterization of Carbon Nanotube Nanoswitches with Gigahertz Resonance Frequency and Low Pull-In Voltages Using Electrostatic Force Microscopy
Application: Transistors
Citation: Miao Lu, Xuekun Lu, Min-Woo Jang, Stephen A. Campbell, Tianhong Cui, Journal of Micromechanics and Microengineering (2010), 20, 105016.
Summary: An electrostatic force microscope (EFM) was used to characterize single-walled carbon nanotube (SWNT)-based nanoswitches in this paper. A conductive atomic force microscopy (AFM) tip acted as a mechanical probe as well as a positioning electrode in the experiment. The resonance frequency of the SWNT beams was computed from the measured SWNTs' dimension and spring constant. The pull-in voltages and the corresponding gaps were extracted simultaneously from a set of force curves at different EFM probe bias voltages. The adhesive force between the AFM tip and the SWNT beam was measured through the analysis of retract force curves. The relationship between the pull-in voltage and the SWNT nanoswitch gap was in agreement with the electrostatic pull-in theory. Long-range forces such as meniscus force or electrostatic force from surface charges engaged the SWNT beam when the gap was below 6 nm in atmosphere. The SWNT beam with a resonance frequency of 1.1 GHz was actuated by a voltage of 2 V for a gap of 6.5 nm. The average adhesive force between an SWNT beam and a platinum/iridium (PtIr5)-coated tip was found to be about 50 nN. Considering the stiffness of the 1.1 GHz SWNT beam, the elastic restoring force at 6.5 nm exceeds 53 nN, which will overcome the adhesive force and release the 1.1 GHz SWNT beam. Finally, some possible approaches to further improve the behavior of SWNT nanoswitches are discussed.
Sorting Carbon Nanotubes by Electronic Structure Using Density Differentiation
Application: CNT Sorting Technologies
Citation: Michael S. Arnold, Alexander A. Green, James F. Hulvat, Samuel I. Stupp, Mark C. Hersam, Nature Nanotechnology (2006), 1, 60-65
Summary: This foundational paper established density gradient ultracentrifugation as the technical and commercial solution to the "carbon nanotube polydispersity" problem. It is the most cited paper in the history of Nature Nanotechnology.
Wafer-Scale Fabrication of Separated Carbon Nanotube Thin-Film Transistors for Display Applications
Application: OLED
Citation: Chuan Wang, Jialu Zhang, Koungmin Ryu, Alexander Badmaev, Lewis Gomez De Arco, Chongwu Zhou, Nano Letters (2009), 9, 12, 4285-4291.
Summary: This paper demonstrates a functioning OLED display device based on a waferscale assembly of carbon nanotube thinfilm transistors. Using IsoNanotubes S 95%, the University of California produced transistors with high yield (>98%), low sheet resistance (25kΩ/sq), high current density ( 10µA/µm), and superior mobility (52 cm 2 V-1s-1). Moreover, on/off rations of >10^4 were achieved in devices with channel length L>20µm. To the best of our knowledge, these are the best concurrent CNT transistor numbers reported in the literature to date.
Thin Film Nanotube Transistors Based on Self-Assembled, Aligned Semiconducting Carbon Nanotube Arrays
Application: Transistors
Citation: Michael Engel, Joshua P. Small, Mathias Steiner, Marcus Freitag, Alexander A. Green, Mark C. Hersam, Phaedon Avouris, ACS Nano (2008), 2, 12, 2445–2452.
Summary: The IBM T.J. Watson Research Center with Northwestern University fabricated thin-film transistors (TFTs) from DGU produced semiconducting CNTs. To confirm the semiconducting purity of the CNTs, the team synthesized 83 single nanotube transistors from the same DGU produced source material. 82 of the 83 transistors were found to contain a semiconducting nanotube, empirically confirming the material's calculated level (99%) of semiconducting enrichment.
Colored Semitransparent Conductive Coatings Consisting of Monodiserse Metallic Single-Walled Carbon Nanotubes
Application: Transparent Conductive Films
Citation: Alexander A. Green, Mark C. Hersam, Nano Letters (2008) 8, 5, 1417-1422.
Summary: This paper discusses the performance of DGU-produced metallic nanotubes in transparent conductive films. In comparison to unsorted-CNT films, metallic films were found to be up to 5.6x more conductive in the visible spectrum, and 10x more conductive in the near infrared (NIR) at similar transparencies.
80 GHz Field-Effect Transistors Produced Using High Purity Semiconducting Single-Walled Carbon Nanotubes
Application: High Frequency Electronic Devices
Citation: L. Nougaret, H. Happy, G. Dambrine, V. Derycke, J. -P. Bourgoin, A. A. Green, M. C. Hersam, Applied Physics Letters (2009) 94, 243505.
Summary: In this study, solutions of 99% pure semiconducting nanotubes were used to fabricate SWNT field-effect transistors (FETs) with extrinsic and intrinsic current gain cutoff frequencies of ~15 and ~80 GHz, respectively. Importantly, this study also demonstrates that precise nanotube alignment is not required to achieve excellent performance in high-frequency devices.
Progress Towards Monodisperse Single-Walled Carbon Nanotubes
Application: CNT Sorting Technologies
Citation:Mark C. Hersam, Nature Nanotechnology (2008) 3, 387-394.
Summary: This paper discusses the advantages of DGU over other nanotube sorting strategies, such as dielectrophoresis, selective chemistry, controlled electrical breakdown, and chromatography. In brief, the principle advantages of DGU are its:
- Demonstrated scalability
- Compatibility with a wide range of starting materials
- Use of reversible functionalization chemistry
- Iterative repeatability
Electrochemical Analysis of Single-Walled Carbon Nanotubes Functionalized with Pyrene-Pendant Transition Metal Complexes
Application: Chemistry
Citation: Eden W. McQueen, Jonas I. Goldsmith, JACS (2009), 131, 48, 17554-17556.
Summary: The noncovalent functionalization of single-walled carbon nanotubes (SWNTs) is important in the development of advanced materials and nanoelectronic sensors and devices. A cobalt-terpyridine transition metal complex with pendant pyrene moieties has been shown to successfully functionalize SWNTs via noncovalent π−π stacking interactions. Cyclic voltammetry at SWNT coated platinum electrodes has been utilized to investigate the process of surface modification and provides conclusive evidence of robust surface functionalization. The electrochemical methodology for examining surface functionalization of SWNTs described herein is generalizable to any redox-active system and provides a simple and powerful means for in situ examination of processes occurring at the surface of nanostructured materials.
Evaluation of Transparent Carbon Nanotube Networks of Homogeneous Electronic Type
Application: Transparent Conductors
Citation: Roderick K. Jackson, Andrea Munro, Kenneth Nebesny, Neal Armstrong, Samuel Graham, ACS Nano (2010), 4, 3, 1377-1384.
Summary: In this report, we present a description of the optical and electronic properties of as-deposited, annealed, and chemically treated single-walled carbon nanotube (SWNT) films showing metallic or semiconducting behavior. As-deposited and annealed semiconducting SWNT films were significantly less conductive than metallic SWNT films; however, chemical treatment of semiconducting SWNT films resulted in sheet resistance values as low as 60 Ω·sq−1 in comparison to 76 Ω·sq−1 for similarly processed metallic SWNT films. We conclude that the greater improvement of electrical conductivity observed in the semiconducting SWNT film results from the difference in the density of available electronic states between metallic and semiconducting SWNTs. A corroborative investigation of the change in surface work function and the chemical composition of SWNT films, as revealed by X-ray photoelectron spectroscopy, is provided to support these conclusions and to give new perspective to the formation of electronically homogeneous SWNT networks.
Enhanced Electromodulation of Infrared Transmittance in Semitransparent Films of Large Diameter Semiconducting Single-Walled Carbon Nanotubes
Application: Optical Transmission
Citation: Feihu Wang, Mikhail E. Itkis, Robert C. Haddon, Nano Letters (2010), 10, 3, 937-942.
Summary: We report a comprehensive study of the gate-induced electromodulated transmittance of infrared light by single-walled carbon nanotube (SWNT) thin films. The observed electromodulation is significantly enhanced by utilizing large diameter SWNTs, increasing the ratio of semiconducting to metal SWNTs, and by decreasing the SWNT film thickness. The amplitude of the effect reported herein (∼7%) is more than an order of magnitude larger than in previous SWNT thin film solid state devices.
Memory Effect of a Single-Walled Carbon Nanotube on Nitride-Oxide Structure Under Various Bias Conditions
Application: Electronics
Citation: Hongsik Park, Hyunjung Shin, Jin Ho Kim, Seungbum Hong, Jimmy Xu, Applied Physics Letters (2010) 96, 023101.
Summary: We report on the memory effect of single-walled carbon nanotubes (SWNTs (placed on a nitride-oxide layer structure designed as a charge storage medium. The conductance of the SWNT was modulated by the injected charge in the nitride-oxide interface and the polarities of injected charges were then detected. A large on/off-state current ratio ≶104(was obtained at a small program/erase voltage range ≶3 V(. We also studied the effect of a half-selected cell on the conductance of the SWNTs to identify the issues with cross-point memory architecture.
Scalable Complementary Logic Gates with Chemically Doped Semiconducting Carbon Nanotube Transistors
Application: Transistors
Citation: Si Young Lee, Sang Won Lee, Soo Min Kim, Woo Jong Yu, Young Woo Jo, Young Hee Lee, ACS Nano (2011), Article ASAP, Currently Web Published.
Summary: Use of random network carbon nanotube (CNT) transistors and their applications to complementary logic gates have been limited by several factors such as control of CNT density, existence of metallic CNTs producing a poor yield of devices, absence of stable n-dopant and control of precise position of the dopant, and absence of a scalable and cost-effective fabrication process. Here, we report a scalable and cost-effective fabrication of complementary logic gates by precisely positioning an air-stable n-type dopant, viologen, by inkjet printing on a separated semiconducting CNTs network. The obtained CNT transistors showed a high yield of nearly 100% with an on/off ratio of greater than 103 in an optimized channel length (9 μm). The n-doped semiconducting carbon nanotube transistors showed a nearly symmetric behavior in the on/off current and threshold voltage with p-type transistors. CMOS inverter, NAND, and NOR logic gates were integrated on a HfO2/Si substrate using the n/p transistor arrays. The gain of inverter is extraordinarily high, which is around 45, and NAND and NOR logic gates revealed excellent output on and off voltages. These series of whole processes were conducted under ambient conditions, which can be used for large-area and flexible thin film technology.
An Ultrasensitive and Low-Cost Graphene Sensor Based on Layer-By-Layer Nano Self-Assembly
Application: Biology
Citation: Bo Zhang and Tianhong Cui, Applied Physics Letters (2011), 98, 073116.
Summary: The flexible cancer sensor based on layer-by-layer self-assembled graphene reported in this letter demonstrates features including ultrahigh sensitivity and low cost due to graphene material properties in nature, self-assembly technique, and polyethylene terephthalate substrate. According to the conductance change of self-assembled graphene, the label free and labeled graphene sensors are capable of detecting very low concentrations of prostate specific antigen down to 4 fg/ml (0.11 fM) and 0.4 pg/ml (11 fM), respectively, which are three orders of magnitude lower than carbon nanotube sensors under the same conditions of design, manufacture, and measurement.
Fundamental Limits on the Mobility of Nanotube-Based Semiconducting Inks
Application: Transistors
Citation: Nima Rouhi, Dheeraj Jain, Katayoun Zand, Peter John Burke, Advanced Materials (2011), 23, 1, 94-99.
Summary: High mobility and high on/off ratio thin-film transistors are fabricated using solution-based deposition of purified semiconducting carbon nanotubes. A comprehensive spectrum of the density starting from less than 10 tubes μm-2 to the high end of around 100 tubes μm-2 is investigated. This study provides the first important roadmap for the tradeoffs between mobility and on/off ratio in nanotube-based semiconducting inks.
A Generalized Method for Evaluating the Metallic-to-Semiconducting Ratio of Separated Single-Walled Carbon Nanotubes by UV−vis−NIR Characterization
Application: Characterization
Citation: Liping Huang, Hongliang Zhang, Bin Wu, Yunqi Liu, Dacheng Wei, Jianyi Chen, Yunzhou Xue, Gui Yu, Hisashi Kajiura, Yongming Li, The Journal of Physical Chemistry (2010), 114, 28, 12095–12098.
Summary:A general and useful method has been developed to evaluate the metallic-to-semiconducting (M/S) ratio for separated single-walled carbon nanotubes (SWNTs). By virtue of measuring UV−vis−NIR spectra of a variety of solutions with different ratios of metallic-rich to semiconducting-rich SWNTs, the commercial IsoNanotubes samples as well as metallic-rich HiPCO SWNTs (HiPCO-M) separated by an Agarose gel method have been evaluated. Values of 99.5% metallic contents for IsoNanotubes-M, 98.9% semiconducting contents for IsoNanotubes-S, and 1.24 for the absorption coefficient of IsoNanotubes, whereas 80.4% metallic contents for HiPCO-M and 1.05 for the absorption coefficient of HiPCO SWNTs were obtained. This method does not need pure metallic (M-) or semiconducting (S-) SWNTs as references. Furthermore, we found that this method can also be applied to evaluate the M/S ratio for any SWNT samples.
Tip-Enhanced Raman Spectroscopic Imaging of Localized Defects in Carbon Nanotubes
Application: Characterization
Citation: Carsten Georgi, Achim Hartschuh, Applied Physics Letters (2010), 97, 143117.
Summary: We used tip-enhanced Raman spectroscopy to study defect induced D-band Raman scattering in metallic single-walled carbon nanotubes with a spatial resolution of 15 nm. The spatial extent of the D-band signal in the vicinity of localized defects is visualized and found to be about 2 nm only. Using the strong optical fields underneath the tip, we photogenerate localized defects and derive a relation between defect density and resulting D-band intensity.
Effect of Source, Surfactant, and Deposition Process on Electronic Properties of Nanotube Arrays
Application: Transistors
Citation: Dheeraj Jain, Nima Rouhi, Christopher Rutherglen, Crystal G. Densmore, Stephen K. Doorn, Peter J. Burke, Journal of Nanomaterials (2011), 10.1155/2011/174268.
Summary: The electronic properties of arrays of carbon nanotubes from several different sources differing in the manufacturing process used with a variety of average properties such as length, diameter, and chirality are studied. We used several common surfactants to disperse each of these nanotubes and then deposited them on Si wafers from their aqueous solutions using dielectrophoresis. Transport measurements were performed to compare and determine the effect of different surfactants, deposition processes, and synthesis processes on nanotubes synthesized using CVD, CoMoCAT, laser ablation, and HiPCO.
Micro Tactile Sensors with a Suspended and Oriented Single Walled Carbon Nanotube Beam Embedded in Polydimethylsiloxane Elastomer
Application: Sensors
Citation: Miao Lu, Dongjin Lee, Taiho Yeom, Tianhong Cui, Sensor Letters (2010), 8, 4, 639-644.
Summary:A tactile sensor utilizing a patterned, aligned, and suspended SWNT film as a sensing element is reported in this paper. The sensor was prepared on both silicon and polymer substrates to expand its potential applications to different working conditions. First, a trench 10 μm deep with Cr/Au electrodes on both sides of the trench was realized. Next, dense and oriented SWNT films were self-assembled using dielectrophoresis through in-situ control of the dc resistance of the film. Follow that, the SWNT film was patterned by lithography and oxygen plasma etching to prepare a suspended SWNT beam. Finally, PDMS primer was spin-coated on the structure and cured to protect the SWNT beam and realize a robust tactile sensor. In nanoindentation test, a piezoresistive sensitivity of 5%/mN and a detection limitation of 2 μN were demonstrated. This simple and low temperature fabrication technology is believed to be very promising for flexible tactile sensor and sensor array in applications to smart robots, implantable clinic tools, or embedded pressure sensors in micro fluidic systems.
Effects of Surfactants on Spinning Carbon Nanotube Fibers by an Electrophoretic Method
Application: CNT Sorting Technologies
Citation: Jun Ma, Jie Tang, Qian Cheng, Han Zhang, Norio Shinya, Lu-Chang Qin, Science and Technology of Advanced Materials (2010), 11, 065005.
Summary: Thin fibers were spun from a colloidal solution of single-walled carbon nanotubes (SWNTs) using an electrophoretic method. Sodium dodecylbenzenesulfonate (NaDDBS) was chosen as a surfactant and showed good performance owing to its special chemical structure. The highest spinning velocity reached 0.5 mm s−1. The resulting SWNT fibers had a tensile strength of 400 MPa and a conductivity of 355 S cm−1. Their mechanical and electrical properties were markedly improved after adding NaDDBS as the dispersant in water.
Large-Scale Simulations of Advanced Materials and Nanoscale Devices
Application: Transistors
Citation: J. Bernholc, M. Buongiorno Nardelli, W. Lu, V. Meunier, W. G. Schmidt, S. Wang, Q. Zhao, DoD UGC (2003), DODUGC.2003.1253364.
Summary: Recent advances in theoretical methods and parallel supercomputing allow for reliable ab initio simulations of the properties of complex materials. We describe two current applications: pyro- and piezoelectric properties of BN nanotubes and optical signatures of organic molecules on Si(001) surface. BN nanotubes turn out to be excellent piezoelectrics, with response values significantly greater than those of piezoelectric polymers. However, their symmetry leads to exact cancellation of the total spontaneous polarization in ideal, isolated nanotubes. Breaking of this symmetry induces spontaneous polarization comparable to those of wurtzite semiconductors. Turning to organics on Si(100), we calculated the atomic structure and the optical signatures of a cyclopentene overlayer on Si(001). Cyclopentene can be used to attach a variety of organic molecules to Si devices, including DNA, and can therefore form a basis of a sensor structure. The spectra turn out to be highly structure-dependent and can therefore be used to monitor interface formation.
The Polarized Carbon Nanotube Thin Film LED
Application: Transistors
Citation: Megumi Kinoshita, Mathias Steiner, Michael Engel, Joshua P. Small, Alexander A. Green, Mark C. Hersam, Ralph Krupke, Emilio E. Mendez, Phaedon Avouris, Opt. Express (2010), 18, 25, 25738-25745.
Summary: We demonstrate a light emitting p-i-n diode made of a highly aligned film of separated (99%) semiconducting carbon nanotubes, self- assembled from solution. By using a split gate technique, we create p- and n-doped regions in the nanotube film that are separated by a micron-wide gap. We inject p- and n-type charge carriers into the device channel from opposite contacts and investigate the radiative recombination using optical micro-spectroscopy. We find that the threshold-less light generation efficiency in the intrinsic carbon nanotube film segment can be enhanced by increasing the potential drop across the junction, demonstrating the LED- principle in a carbon nanotube film for the first time. The device emits infrared light that is polarized along the long axes of the carbon nanotubes that form the aligned film.