Thesis defence in the University of Oulu

Doctoral Candidate

Master of Science Olli Pitkänen

Faculty and research unit

University of Oulu Graduate School, Faculty of Information Technology and Electrical Engineering, Microelectronics research unit

Field of study

Electronics materials & components

Date and time of the thesis defence

16.8.2019 12:00

Place of the thesis defence

University of Oulu, Arina auditorium (TA105), Linnanmaa

Topic of the dissertation

On-device synthesis of customized carbon nanotube structures

Opponent

Doctor Asta Kärkkäinen, Huawei Technologies

Second opponent

Professor Albert Nasibulin, Skolkovo Institute of Science and Technology

Custos

Professor Krisztian Kordas, University of Oulu

Direct growth of carbon nanotubes on substrates

Carbon nanotubes are known for their excellent mechanical and electrical properties, that have fostered a vast number of applications during the last two decades. Direct integration of CNTs into devices is not straightforward, as high growth temperatures (over 600 centigrade) challenge the stability of the applied substrate. However, by decreasing growth temperature and working out protocols that take into account the thermal stability of the materials involved, it is possible to create several new types of architectures and devices with functionalities not shown before. In this work, we show that, with selection of the appropriate substrate, diffusion barrier and catalyst materials, direct growth of functional CNT films and their micropatterns may be achieved, not only on Si chips, but also on other atypical surfaces, using chemical vapor deposition.

This thesis explores low-temperature Carbon nanotube growth over bi- and trimetallic catalysts and investigates the effect of barrier layers on the electrical properties of substrate-to-nanotube contacts. On one hand, the lowest achieved carbon nanotube growth temperature (400 centigrade) is compatible with most silicon technologies, thus enabling direct integration of CNTs with materials that are not compatible with high temperatures. On the other hand, the results of barrier layer studies enabled growth of carbon nanotubes on metals for supercapacitors applications. In addition, we also show a method where laser-treatment of steel and superalloy surfaces enabled micropatterned carbon nanotube growth. Furthermore, we present CNT growth on carbon materials and demonstrate entirely carbon-based hierarchical composites for electromagnetic interference shielding applications, exhibiting outstanding shielding performance.

Dissertation

Last updated: 6.8.2019