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Carbon Nanotube Transistors: Nanotube Growth, Contact Properties and Novel Devices

Abstract
Carbon nanotubes (CNTs) are envisioned to be used as the basic building blocks in future electronics due to their excellent electronic properties such as high mobility, compatibility with high-k dielectrics and small diameters resulting in advantageous electrostatics. This thesis is divided into three separate topics related to increasing the fabrication yield and performance of CNT field effect transistors (CNTFETs). The first part describes a method to control the orientation of CNTs during chemical vapour deposition (CVD) using an electric field. Under certain experimental conditions, deformations in the SiO2 substrate are formed in the vicinity of the CNTs. An explanation based on field emission from the growing CNTs and Marangoni convection and capillary waves in the molten SiO2 underneath agrees well with the observed structural changes. In the second part, CNTFETs that employ CNTs as gate electrodes are described. Devices have been fabricated both by combining electric field directed growth with dielectrophoretic deposition and by a technique with two successive CVD steps. The use of a CNT gate gives an improved inverse subthreshold slope compared to using a back gate and a gate delay of 5 ps. The measured characteristics agree well with theoretical modeling which also asserts that the gate delay can be lowered to 2 ps by reducing the thickness of the gate dielectric. The final part describes a study of the Schottky barriers between Pd contacts and semiconducting CNTs measured using temperature dependent electrical characterisation. It is found that the barrier heights are close to those expected without Fermi level pinning and inversely proportional to CNT diameter.
Parts of work
I. S. Dittmer, J. Svensson and E. E. B. Campbell. Electric field aligned growth of single-walled carbon nanotubes. Current Applied Physics, 4, 595-598 (2004)::doi::10.1016/j.cap.2004.01.026
 
II. J. Svensson, N. M. Bulgakova, O. A. Nerushev and E. E. B. Campbell. Marangoni effect in SiO2 during field-directed chemical vapor deposition growth of carbon nanotubes. Physical Review B, 73, 205413 (2006)::doi::10.1103/PhysRevB.73.205413
 
III. J. Svensson, N. M. Bulgakova, O. A. Nerushev and E. E. B. Campbell. Field emission induced deformations in SiO2 during CVD growth of carbon nanotubes. Physica Status Solidi (b), 243, (13), 3524-3527 (2006)::doi::10.1002/pssb.200669114
 
IV. D. S. Lee, J. Svensson, S. W. Lee, Y. W. Park and E. E. B. Campbell. Fabrication of Crossed Junctions of Semiconducting and Metallic Carbon Nanotubes: A CNT-Gated CNT-FET. Journal of Nanoscience and Nanotechnology, 6, (5), 1325-1330 (2006)::doi::10.1166/jnn.2006.321
 
V. J. Svensson, Yu. Tarakanov, D S. Lee, J. M. Kinaret, Y W. Park and E. E. B. Campbell. A carbon nanotube gated carbon nanotube transistor with 5 ps gate delay. Nanotechnology, 19, 325201 (2008)::doi::10.1088/0957-4484/19/32/325201
 
VI. J. Svensson, A. A. Sourab, Yu. Tarakanov, D S. Lee, S J. Park, S J. Baek, Y W. Park and E. E. B. Campbell The dependence of the Schottky barrier height on carbon nanotube diameter for Pd-carbon nanotube contacts. Nanotechnology, 20, 175204 (2009)::doi::10.1088/0957-4484/20/17/175204
 
Degree
Doctor of Philosophy
University
Göteborgs universitet. Naturvetenskapliga fakulteten
Institution
Department of Physics ; Institutionen för fysik
Disputation
Fredagen den 7 maj 2010, kl 10.15, Kollektorn, MC2 Chalmers, Kemivägen 9
Date of defence
2010-05-07
E-mail
johannes@physics.gu.se
URI
http://hdl.handle.net/2077/21859
Collections
  • Doctoral Theses / Doktorsavhandlingar Institutionen för fysik
  • Doctoral Theses from University of Gothenburg / Doktorsavhandlingar från Göteborgs universitet
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main thesis file (5.970Mb)
abstract (44.27Kb)
Date
2010-04-13
Author
Svensson, Johannes
Keywords
Carbon nanotube
chemical vapour deposition
Field effect transistor
Marangoni convection
Schottky barrier
Publication type
Doctoral thesis
ISBN
978-91-628-8013-2
Language
eng
Metadata
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