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Dissertation bulletin: Applying a semiconductor technique to carbon nanotube films led to unexpected results

Dissertation title
Nitrogen-doped single-walled carbon nanotube thin films
(Typpiseostettujen yksiseinäisten hiilinanoputkien ohutkalvot)
Dissertation contents
Transparent electrically conducting films are essential components in countless touch screens. Nowadays these films are made of indium tin oxide, which has several disadvantages, most significantly the limited world resources of indium. Carbon nanotubes – molecular cylinders only tens of atoms in circumference but millions of times longer – are one of the promising alternatives offered by nanotechnology.

However, one of the special features of nanotubes is that their exact atomic configuration determines whether they are semiconducting or metallic. Depending on the application, only one type is suitable. For example, conducting thin films require metallic nanotubes. Despite intense research efforts, synthesis methods have not advanced to the level where only the desired type could be grown. But it is known from semiconductor technology that the electrical properties of semiconductors can be controlled by doping them with atoms that have either more or less outer shell electrons than the host atoms. This insight has been applied to nanotubes as well. As they are made of carbon, nitrogen is the most appealing dopant atom due to it's sinle extra electron and suitable atomic size.

As part of the dissertation research, nitrogen-doped carbon nanotube thin films were synthesized and their applicability for transparent conducting films studied. Surprisingly it turned out that nitrogen doping did not increase the conductivity of the films, but rather decreased it significantly. It is thought that this is due to significantly enhanced scattering of the charge carriers by the nitrogen atoms in the one-dimensional nanotubes. This finding will for it's part direct the use of nitrogen-doped nanotubes into alternative directions, such as sensor or composite applications.

Dissertation area
Toma Susi, DI
Defence time
20.05.2011 at 12 noon
Aalto University School of Science, Computer Science Building, Auditorium T2, Konemiehentie 2, Espoo
Professor Mauricio Terrones, Penn State University, USA
Professor Esko I. Kauppinen, Aalto University School of Science, Department of Applied Physics, NanoMaterials Group
Dissertation url
Candidate contact info
Toma Susi
PL 15100 (Puumiehenkuja 2)
00076 Aalto