Hall effect in carbon nanotube thin films

• Published in: Synthetic metals 2014-12, Vol.198, p.84-87
• Main Authors: Lee, Seung Hyun, Uhm, Tae Woo, You, Young Gyu, Kim, Sung Won, Jhang, Sung Ho, Dettlaff-Weglikowska, Urszula, Park, Yung Woo
• Format: Article
• Language: English
• Subjects: Carbon nanotube; Carrier density; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electric potential; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in multilayers, nanoscale materials and structures; Exact sciences and technology; Hall effect; Magnetic fields; Magnetoresistance; Magnetoresistivity; Majority carriers; Mathematical analysis; Nanotubes; Physics; Thin films; Voltage
• ISSN: 0379-6779; 1879-3290
• DOI: 10.1016/j.synthmet.2014.10.001

We have investigated Hall coefficient and magnetoresistance in thin films of single-walled carbon nanotubes, prepared in four different ways. Hall voltages are linear for all samples in magnetic fields up to 6 T, and the measured carrier density lies in ∼1021–1022cm−3. Whereas earlier Hall-effect experiments reported ∼1018–1019cm−3 for the carrier density, our results are consistent with the theoretically predicted value of ∼1022cm−3, calculated for the aligned metallic CNTs. The signs of the Hall coefficients are positive in general, indicating that majority carriers are holes in these films. In a nanotube film with the lowest conductivity, however, we find the Hall coefficient reverses the sign at low temperature around T=15K. The origin of the sign change is not clear. In strongly localized regime, the Hall effect can be anomalous.