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Nanotransducers and Nanosystems

The objectives of the research on nanotransducers and nanosytems are the exploration of novel growth processes and the evaluation of electronic, mechanical and electromechanical properties of single-walled carbon nanotubes as active elements in electromechanical transducers. Integrated Nano Electro-Mechanical Systems (NEMS) are proposed, which will be used to study the properties of nanotransducers, which are preferably integrated into MEMS, for sensing applications.

Current Research Focus Areas in Nanotransducers an Nanosystems

Ultraclean Carbon Nanotubes Devices

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Individual single-walled carbon nanotubes can be utilized as mechanical sensors elements for large strain levels.  In this work, the suspended nanotubes are strained by micro actuators and exhibit field-effect transistors operation free of gate hysteresis even at humid ambient air– facilitating the assessment of piezoresistive effects.

In addition to Raman spectroscopy, transmission electron microscopy (TEM) is used for device characterization including chirality assignment by electron diffraction – relevant for comparing theory and experimental sensor performance.

To integrate nanotubes in a clean manner, the nanotubes are directly grown across micro actuated supports and electrically interfaced using resist-free on-chip shadow masking.

Alternatively, contamination-free transfer of pristine nanotubes avoids exposing the device chip to high temperature during nanotube synthesis and provides improved nanotube orientation.

For further details please refer to the research database of the ETH, or contact Matthias Muoth

  Selected and Latest Publications on this topic:

[1] M. Muoth, "Clean integration of single-walled carbon nanotubes for electromechanical systems," Dissertation for the degree of Doctor of Sciences, D-MAVT, Diss. ETH, 20887, ETH Zurich, Zurich, 2013. Submitted.

[2] M. Muoth, C. Kiran, Y. Liu, and C. Hierold, "Suspended CNT-FET piezoresistive strain gauges: Chirality assignment and quantitative analysis," in IEEE MEMS 2013, Taipei, Taiwan, pp. 496-499, 2013.

[3] M. Muoth, T. Helbling, L. Durrer, S. W. Lee, C. Roman, and C. Hierold, "Hysteresis-free operation of suspended carbon nanotube transistors," Nature Nanotechnology, vol. 5, pp. 589-592, 2010.

[4] J. Cai, P. Ruffieux, R. Jaafar, M. Bieri, T. Braun, S. Blankenburg, M. Muoth, A. P. Seitsonen, M. Saleh, X. Feng, K. Mullen, and R. Fasel, "Atomically precise bottom-up fabrication of graphene nanoribbons," Nature, vol. 466, pp. 470-473, 2010.

[5] M. Muoth, F. Gramm, K. Asaka, L. Durrer, T. Helbling, C. Roman, S. W. Lee, and C. Hierold, "Chirality assignment to carbon nanotubes integrated in MEMS by tilted-view transmission electron microscopy," Sensors and Actuators B: Chemical, vol. 154, pp. 155-159, 2011.

Carbon Nanotube FET-based Sensors

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The Micro and Nanosystems Group has several focus areas in the general domain of carbon nanotube field effect transistor (CNFET) sensors. This is based upon an established competency in CNFET fabrication, integration, and characterization (see publications).

Pressure Sensors:

The high gauge factors of single-walled carbon nanotubes (SWNTs) allow them to sense the deformations of membranes due to ambient pressure gradients. In this work, this feature of SWNTs is employed in the development of ultra-small pressure sensors for medical applications. These devices make use of the minute size and low power consumption of SWNTs.

One of the main challenges is the integration of a diaphragm as the electromechanical transducer element. In order to make use of the small size of SWNTs, the dimensions of this diaphragm must be smaller than the state-of-the-art in MEMS pressure sensors.

Alumina diaphragms with diameters down to 2 mm have been fabricated by atomic layer deposition, and the electrical integration of these devices is currently under investigation.

For further details please refer to the research database of the ETH, or contact Tobias Suess

Previous projects in this topic:

Ultra-miniature pressure sensors with single-walled carbon nanotubes (SWNTs) as the functional transducer element

Gas Sensors:

Carbon nanotube chemical sensors promise incredibly low operating power compared to existing technologies, in addition to their small size.  By analyzing the change the in electrical transport characteristics of single-walled carbon nanotubes (SWNTs) upon exposure to gaseous analytes (e.g. NO2), carbon nanotube-based field-effect transistor devices are employed as chemical sensors.

For further details please refer to the research database of the ETH, or contact Kiran Chikkadi or Wei Liu

Ciliary Flow Sensors:

The objective of this work is the exploration of a novel micro scale ciliary flow sensor. The sensor concept combines small cilia (sensor hairs) with the exceptional physical properties of carbon nanotubes to reach dimensions similar to those of the acoustic flow transducers in the inner ear of mammals.

Estimations suggest that such a transducer has a great potential to become a building block for future applications, such as biomimetic cochlear implants and biomimetic microphones. In order to evaluate the suitability for applications, the relevant carbon nanotube properties are investigated, culminating in the

design, demonstration, and characterization of a prototype device.

For further details please refer to the research database of the ETH, or contact Valentin Doering

  Selected and Latest Publications on this topic:

Pressure Sensors:

[1] T. Süss and C. Hierold, "Development of ultra-small thin film diaphragms for pressure sensor applications," 23rd Micromechanics and Microsystems Europe Workshop (MME 2012), Sep. 9-12, Ilmenau, Germany, 2012.

[2] M. Haluška, M. Muoth, W. Liu, K. Chikkadi, M. Mattmann, M. Politou, T. Süss, and C. Hierold, "Fabrication of carbon nanotube field effect transistors based on individual SWCNT for NO2 sensor applications," E-MRS 2012 FALL MEETING, Sep. 17-21, Warsaw, Poland, 2012.

Gas Sensors:

[1] K. Chikkadi, C. Roman, L. Durrer, T. Süss, R. Pohle, C. Hierold, ‘Scalable fabrication of individual SWNT chem-FETs for gas sensing’, Procedia Engineering (Eurosensors XXVI), 2012, Krakow, Poland

Ciliary Flow Sensors:

[1] V. Döring and C. Hierold, "Patterning of SU-8 Pillars with Submicron Widths by Electron Beam Lithography at 20 and 30 kV," in Smart Systems Integration, Zurich, 2012.

Large-scale Fabrication and Integration of Carbon Nanotubes

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In this work, fabrication and integration processes for single-walled carbon nanotube (SWNT) devices are developed to improve device robustness and yield. This work is oriented towards

creating device arrays based on SWNTs and other large scale integration scenarios. This work includes investigations into the ability to control or select SWNTs based on parameters such as SWNT length, chirality, and electrical transport characteristics.

Additionally, contacts and interfaces between SWNTs and gate dielectrics, passivation layers, and growth substrates are studied for optimization of SWNT electrical inerfacing and integration.

For further details please refer to the research database of the ETH, or contact Kiran Chikkadi , Dr. Miroslav Haluska, Dr. Emine Cagin or Matthias Muoth

Previous projects in this topic:

Integrated nano transducers: fundamental characterization of electromechanical effects in carbon nanotubes

   Selected and Latest Publications on this topic:

[1] K. Chikkadi, M. Mattmann, M. Muoth, L. Durrer, C. Hierold, ‘The role of pH in the density control of ferritin-based catalyst nanoparticles towards scalable single-walled carbon nanotube growth’, Microelectronic Engineering 88 (2011), pp. 2478-2480

[2] K. Chikkadi, C. Roman, C. Hierold, ‘Process control monitors for single-walled carbon nanotube based sensor fabrication processes’, Proceedings of the 26th IEEE conference on Microelectromechanical Systems (MEMS 2013), Taiwan, 2013 (accepted)

[3] M. Mattmann, D. Bechstein, C. Roman, K. Chikkadi, C. Hierold, ‘Reduction of gate hysteresis above ambient temperature via ambipolar pulsed gate sweeps in carbon nanotube field effect transistors for sensor applications’, Applied Physics Letters 97(15), 153103, 2010

Carbon Nanotube Electromechanical Resonators

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The acoustic resonances of suspended single-walled nanotubes (SWNTs) can be used to detect the mass of individual atoms or to detect ultra-small strains.

This work focuses on the use strain-engineered SWNT resonator structures for the detection of nanoscale quantities while also tuning resonator parameters such as

Q-factor, resonance frequency and presence of nanotube slack. The expected increase in performance from the tuning of these parameters will be used towards the employment of SWNT resonators as practical sensors.

For further details please refer to the research database of the ETH, or contact Shih-Wei Lee or contact Dr. Stuart Truax

  Selected and Latest Publications on this topic:

[1] Chandrahalim, H., C.I. Roman, and C. Hierold. Analytic modeling and piezoresistive detection theory of acoustic resonances in carbon nanotubes. in Nanotechnology (IEEE-NANO), 2010 10th IEEE Conference on. 2010.


Completed projects:

 

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