Narrowing SWNT diameter distribution using size-separated ferritin-based Fe catalysts.
Sensors and devices made from single-walled carbon nanotubes (SWNTs) are most often electrically probed through metal leads contacting the semiconducting SWNTs (s-SWNTs). Contact barriers in general and Schottky barriers (SBs) in particular are usually obtained at a metal-semiconductor interface. The unique one-dimensional structure (1D) of SWNTs allows tailoring of the SB heights through the contact metal type and the size of the s-SWNT bandgap. A large workfunction reduces the SB height (e.g. using Pd as the metal contact material). The bandgap of an SWNT is inversely proportional to its diameter. Ohmic contacts--the preferable choice--are achieved for s-SWNTs with diameters greater than 2 nm on Pd metal leads. SWNT device reproducibility, on the other hand, requires a narrow distribution of the SWNT diameters. Here, we present a method to fabricate SWNTs with a large and adjustable mean diameter (1.9-2.4 nm) and very narrow diameter distribution (+/- 0.27 nm at mean diameter 1.9 nm). The results are achieved through a size separation of the ferritin catalyst particles by sedimentation velocity centrifugation prior to their use in the chemical vapor deposition (CVD) formation of SWNTs.
Durrer
Lukas
L
Micro and Nanosystems, Department of Mechanical and Process Engineering, ETH Zürich, Zurich, Switzerland. lukas.durrer@micro.mavt.ethz.ch
Greenwald
Jason
J
Helbling
Thomas
T
Muoth
Matthias
M
Riek
Roland
R
Hierold
Christofer
C
D000818:Animals; D002384:Catalysis; D002498:Centrifugation; D005290:Ferric Compounds / Q000378:metabolism; D005293:Ferritins / Q000302:isolation & purification*; D006736:Horses; D007501:Iron / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D053758:Nanoparticles / Q000648:ultrastructure; D037742:Nanotubes, Carbon / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size
D005290:Ferric Compounds; D037742:Nanotubes, Carbon; C000499:ferric oxide; D005293:Ferritins; D007501:Iron