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Ink-jet printing of thin film transistors based on carbon nanotubes
KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.ORCID iD: 0000-0002-6430-6135
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The outstanding electrical and mechanical properties of single-walled carbon nanotubes (SWCNTs) may offer solutions to realizing high-mobility and high-bendability thin-film transistors (TFTs) for the emerging flexible electronics. This thesis aims to develop low-cost ink-jet printing techniques for high-performance TFTs based on pristine SWCNTs. The main challenge of this work is to suppress the effects of “metallic SWCNT contamination” and improve the device electrical performance. To this end, this thesis entails a balance between experiments and simulations.

 

First, TFTs with low-density SWCNTs in the channel region are fabricated by utilizing standard silicon technology. Their electrical performance is investigated in terms of throughput, transfer characteristics, dimensional scaling and dependence on electrode metals. The demonstrated insensitivity of electrical performance to the electrode metals lifts constrains on choosing metal inks for ink-jet printing.

 

Second, Monte Carlo models on the basis of percolation theory have been established, and high-efficiency algorithms have been proposed for investigations of large-size stick systems in order to facilitate studies of TFTs with channel length up to 1000 times that of the SWCNTs. The Monte Carlo simulations have led to fundamental understanding on stick percolation, including high-precision percolation threshold, universal finite-size scaling function, and dependence of critical conductivity exponents on assignment of component resistance. They have further generated understanding of practical issues regarding heterogeneous percolation systems and the doping effects in SWCNT TFTs.

 

Third, Monte Carlo simulations are conducted to explore new device structures for performance improvement of SWCNT TFTs. In particular, a novel device structure featuring composite SWCNT networks in the channel is predicted by the simulation and subsequently confirmed experimentally by another research group. Through Monte Carlo simulations, the compatibility of previously-proposed long-strip-channel SWCNT TFTs with ink-jet printing has also been demonstrated.

 

Finally, relatively sophisticated ink-jet printing techniques have been developed for SWCNT TFTs with long-strip channels. This research spans from SWCNT ink formulation to device design and fabrication. SWCNT TFTs are finally ink-jet printed on both silicon wafers and flexible Kapton substrates with fairly high electrical performance.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , xiv, 58 p.
Series
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2010:08
Keyword [en]
Single-walled carbon nanotube, thin film transistor, ink-jet printing, Monte Carlo simulation, stick percolation, composite network, flexible electronics
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-24427ISBN: 978-91-7415-717-8 (print)OAI: oai:DiVA.org:kth-24427DiVA: diva2:349716
Public defence
2010-09-24, Sal D, KTH Forum, Isafjordsgatan 39, Kista, 13:15 (English)
Opponent
Supervisors
Note
QC 20100910Available from: 2010-09-10 Created: 2010-09-08 Last updated: 2010-09-10Bibliographically approved
List of papers
1. Percolation in random networks of heterogeneous nanotubes
Open this publication in new window or tab >>Percolation in random networks of heterogeneous nanotubes
2007 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 253127Article in journal (Refereed) Published
Abstract [en]

The electrical performance of random carbon nanotube network transistors is found by Monte Carlo simulation to strongly depend on the nature of the conduction path percolating the network. When the network is percolated only by semiconducting nanotube pathways (OSPs), the transistors can directly achieve both high on current and large on/off current ratio. Based on percolation theory, the present work predicts that there exist specific nanotube coverage domains within which OSP has the highest probability and becomes predominant. Simulation results show that the coverage domains depend on the network dimension, nanotube length, and the fraction of metallic nanotubes.

Keyword
metallic carbon nanotubes, thin-film transistors, aligned arrays, electronics
Identifiers
urn:nbn:se:kth:diva-17179 (URN)10.1063/1.2827577 (DOI)000251908100094 ()2-s2.0-37549027980 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-10Bibliographically approved
2. Contact-electrode insensitive rectifiers based on carbon nanotube network transistors
Open this publication in new window or tab >>Contact-electrode insensitive rectifiers based on carbon nanotube network transistors
2008 (English)In: IEEE Electron Device Letters, ISSN 0741-3106, E-ISSN 1558-0563, Vol. 29, no 5, 500-502 p.Article in journal (Refereed) Published
Abstract [en]

This letter presents rectifiers based on the diode connection of carbon nanotube network (CNN) transistors. Despite a low density of carbon nanotubes in the CNNs, the devices can achieve excellent performance with a forward/reverse current ratio reaching 10(5). By casting nanotube suspension on oxidized Si substrates with predefined electrodes, CNN-based field-effect transistors are readily prepared. By short-circuiting the source and gate terminals, CNN-based rectifiers are realized with the rectification characteristics independent of whether Pd or Al is employed as the contact electrodes. This independence is especially attractive for applications of CNN-based transistors/rectifiers in flexible electronics with various printing techniques.

Keyword
carbon nanotube (CNT), field-effect transistor, random network of CNTs, rectifier, single-walled CNT (SWCNT), thin-film transistors, nanomaterials
Identifiers
urn:nbn:se:kth:diva-17477 (URN)10.1109/led.2008.920279 (DOI)000255317400025 ()2-s2.0-43549125771 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-10Bibliographically approved
3. Distinguishing self-gated rectification action from ordinary diode rectification in back-gated carbon nanotube devices
Open this publication in new window or tab >>Distinguishing self-gated rectification action from ordinary diode rectification in back-gated carbon nanotube devices
2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 133111Article in journal (Refereed) Published
Abstract [en]

Self-gating leading to rectification action is frequently observed in two-terminal devices built from individual or networked single-walled carbon nanotubes (SWCNTs) on oxidized Si substrates. The current-voltage (I-V) curves of these SWCNT devices remain unaltered when switching the measurement probes. For ordinary diodes, the I-V curves are symmetric about the origin of the coordinates when exchanging the probes. Numerical simulations suggest that the self-gated rectification action should result from the floating semiconducting substrate which acts as a back gate. Self-gating effect is clearly not unique for SWCNT devices. As expected, it is absent for devices fabricated on insulating substrates.

Keyword
thin-film transistors, single, networks, junctions
Identifiers
urn:nbn:se:kth:diva-17433 (URN)10.1063/1.2906367 (DOI)000254669900079 ()2-s2.0-41649115409 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-10Bibliographically approved
4. Improved electrical performance of carbon nanotube thin film transistors by utilizing composite networks
Open this publication in new window or tab >>Improved electrical performance of carbon nanotube thin film transistors by utilizing composite networks
2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 133103Article in journal (Refereed) Published
Abstract [en]

This work presents a simple scheme of using composite carbon nanotube networks (c-CNNs) to significantly improve the electrical performance of long-channel thin film transistors based on single-walled carbon nanotubes (SWCNTs). Such c-CNNs comprise two sets of SWCNTs. A primary set consists of dense arrays of perfectly aligned long SWCNTs along the transistor channel direction. A secondary set is composed of short SWCNTs either randomly orientated or perpendicularly aligned with respect to the channel. While retaining a high on/off current ratio, the drive current in such c-CNNs is much higher than that in currently studied systems with single CNNs or SWCNT arrays.

Keyword
aligned arrays, large-scale, electronics
Identifiers
urn:nbn:se:kth:diva-17432 (URN)10.1063/1.2905270 (DOI)000254669900071 ()2-s2.0-41649089748 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-10Bibliographically approved
5. Understanding doping effects in biosensing using carbon nanotube network field-effect transistors
Open this publication in new window or tab >>Understanding doping effects in biosensing using carbon nanotube network field-effect transistors
2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 155434Article in journal (Refereed) Published
Abstract [en]

Systematic theoretical studies based on a comprehensive heterogeneous stick percolation model are performed to gain insights into the essence of doping effects in electrical sensing of biomolecules, such as proteins and DNA fragments, using carbon nanotube network field-effect transistors (CNNFETs). The present work demonstrates that the electrical response to doping of CNNFETs is primarily caused by conductance change at the electrode-nanotube contacts, in contrast to that in the channel as assumed previously. However, the presence of intertube junctions in the channel could reduce the sensitivity of CNNFET-based biosensors and is partially responsible for the experimentally observed channel-length dependent sensitivity.

Keyword
biosensors, carbon nanotubes, DNA, doping, field effect transistors, molecular biophysics, nanocontacts, nanotube devices, percolation, proteins, thin-film transistors, contact resistance, devices, transition, transport, density, scale
Identifiers
urn:nbn:se:kth:diva-18411 (URN)10.1103/PhysRevB.79.155434 (DOI)000265944200123 ()2-s2.0-66149183139 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
6. Finite-size scaling in stick percolation
Open this publication in new window or tab >>Finite-size scaling in stick percolation
2009 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 80, no 4Article in journal (Refereed) Published
Abstract [en]

This work presents the generalization of the concept of universal finite-size scaling functions to continuum percolation. A high-efficiency algorithm for Monte Carlo simulations is developed to investigate, with extensive realizations, the finite-size scaling behavior of stick percolation in large-size systems. The percolation threshold of high precision is determined for isotropic widthless stick systems as N(c)l(2)=5.637 26 +/- 0.000 02, with N-c as the critical density and l as the stick length. Simulation results indicate that by introducing a nonuniversal metric factor A=0.106 910 +/- 0.000 009, the spanning probability of stick percolation on square systems with free boundary conditions falls on the same universal scaling function as that for lattice percolation.

Keyword
lattice theory, Monte Carlo methods, percolation, probability, continuum percolation, spanning probability, threshold, system, universality, nanotubes, computer
Identifiers
urn:nbn:se:kth:diva-18918 (URN)10.1103/PhysRevE.80.040104 (DOI)000271350400004 ()2-s2.0-70449134042 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
7. Conductivity exponents in stick percolation
Open this publication in new window or tab >>Conductivity exponents in stick percolation
2010 (English)In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 81, no 021120Article in journal (Refereed) Published
Abstract [en]

On the basis of Monte Carlo simulations, the present work systematically investigates how conductivity exponents depend on the ratio of stick-stick junction resistance to stick resistance for two-dimensional stick percolation. Simulation results suggest that the critical conductivity exponent extracted from size-dependent conductivities of systems exactly at the percolation threshold is independent of the resistance ratio and has a constant value of 1.280 +/- 0.014. In contrast, the apparent conductivity exponent extracted from density-dependent conductivities of systems well above the percolation threshold monotonically varies with the resistance ratio, following an error function, and lies in the vicinity of the critical exponent.

Keyword
alexander-orbach conjecture, thin-film transistors, walled carbon, nanotubes, continuum percolation, random networks, 3 dimensions, system, transparent, computer
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-19272 (URN)10.1103/PhysRevE.81.021120 (DOI)000275053700032 ()
Funder
Swedish Research Council, 2009-8068
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
8. Ink-jet printed thin-film transistors with carbon nanotube channels shaped in long strips
Open this publication in new window or tab >>Ink-jet printed thin-film transistors with carbon nanotube channels shaped in long strips
Show others...
2011 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 8, 084915Article in journal (Refereed) Published
Abstract [en]

The present work reports on the development of a class of sophisticated thin-film transistors (TFTs) based on ink-jet printing of pristine single-walled carbon nanotubes (SWCNTs) for the channel formation. The transistors are manufactured on oxidized silicon wafer and flexible plastic substrates at ambient conditions. For this purpose, ink-jet printing techniques are developed aiming at high-throughput production of SWCNT thin-film channels shaped in long strips. Stable SWCNT inks with proper fluidic characteristics are formulated by polymer addition. The present work unveils, through Monte Carlo simulation and in the light of heterogeneous percolation, the underlying physics of the superiority of long-strip channels for SWCNT TFTs. It further predicts the compatibility of such a channel structure with ink-jet printing taking into account the minimum dimensions achievable by commercially available printers. The printed devices exhibit improved electrical performance and scalability, compared to previously reported ink-jet printed SWCNT TFTs. The present work demonstrates that ink-jet printed SWCNT TFTs of long-strip channels are promising building blocks for flexible electronics.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2011
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-24431 (URN)10.1063/1.3569842 (DOI)000290047000242 ()2-s2.0-79955723280 (Scopus ID)
Note

QC 20110609

Available from: 2010-09-08 Created: 2010-09-08 Last updated: 2017-12-12Bibliographically approved

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