El Dr. Miro Haluska  de Micro and Nanosystems ETH en Zurich,  Suiza dará una conferencia el 13 de Julio en el  ICB-CSIC: Monitoring the integration process of individual single-walled carbon nanotubes into sensing devices.

El Seminario tendrá lugar en el salón de actos del ICB-CSIC, Zaragoza.

Jueves 13 de Julio, 12:30

RESUMEN:

Monitoring the integration process of individual single-walled carbon nanotubes into sensing devices 

Miro Haluska, Wei Liu, Sebastian Eberle, Lalit Kumar, Laura Vera Jenni, Pooriya Gh Ghanbari, Pol Peiffer, Cosmin Roman, Christofer Hierold.   Micro and Nanosystems ETH Zürich, Tannenstrasse 3, 8092 Zurich, Switzerland

Our nanotube devices (gas sensors and nanoresonators) are based on individual single-walled carbon nanotubes (SWCNTs) and were fabricated either by standard photo- or electron-beam lithography, or by ultra-clean mechanical transfer from dedicated growth substrates onto the final devices [1]. SWCNTs were synthesized on SiO2/Si chips or SOI structures from ferritinbased Fe catalyst nanoparticles by LPCVD at 850°C in CH4/H2 [2]. As-grown suspended SWCNTs were visualized by post-synthesis deposition of volatile nanoparticles and inspected by optical microscopy and by Raman spectroscopy. For the optical microscopic visualization we used a para-nitrobenzoic acid (pNBA) based approach as introduced in [3]. Substrate bound CNTs were pre-characterized by AFM and Raman spectroscopy. The combination of this visualization and characterization methods allows for the determination of the position of CNTs with respect to predefined chip structures and the selection of pre-characterized nanotubes for further device fabrication.

Devices based on individual SWCNTs often do not perform as expected from nanotubes’ outstanding intrinsic properties. Additionally, variations in electrical characteristics of individual carbon nanotube field effect transistors (iCNFETs), cannot be explained solely by the variation in intrinsic properties of different SWCNTs [4]. Both above-mentioned observations can be caused by physical and chemical impacts of device fabrication processes on SWCNTs. To monitor the impact of the device fabrication, selected SWCNTs were characterized by Raman spectroscopy after individual processing steps. By this approach we determined, for example, the minimum thickness of sacrificial alumina layer required to protect SWCNTs from the impact of plasma ashing used for removing lithography resist residuals [5]. Using the process flow monitoring for optimization of the device fabrication helped narrowing the variation of devices resistance and 1.8 times improvement in median value of device resistance.

References:

1. Muoth, M., Hierold, C., (2012). Transfer of carbon nanotubes onto microactuators for hysteresisfree transistors at low thermal budget. IEEE MEMS 2012, Paris, pp 1352-1355.
2. Durrer, L., Greenwald, J., Helbling, T., Muoth, M., Riek, R., Hierold, C., (2009). Narrowing SWNT diameter distribution using size-separated ferritin-based Fe catalysts. Nanotechnology 20, 355601-7
3. Zeevi, G., et al., (2016) Automated circuit fabrication and direct characterization of carbon nanotube vibrations. Nature Comms. Art Nr.: 12153, DOI: 10.1038/ncomms12153.
4. Park, H., Afzali, A., Han S.J., Tulevski, G.S., Franklin, A.D., Tersoff, J., Hannon J.B., Haensch, W., (2012). High-density integration of carbon nanotubes via chemical self-assembly. Nature nanotechnology 7, 787-791.
5. Liu, W., Chikkadi, K., Hierold, C., Miroslav Haluska, (2016) Enabling fabrication of clean electrical contacts to carbon nanotubes using oxygen plasma ashing. physica status solidi b, 253, 2417-2423.