1. Fundamental aspects of adsorption on individual carbon nanotubes
David Cobden, Department of Physics, University of Washington
Molecules such as oxygen, when adsorbed on graphite at low temperatures, can move freely over its surface and form distinct monolayer phases which are two-dimensional (2D) analogs of 3D solids and liquids. Sharp phase transitions occur as a function of 2D density. Our aim is to use single-walled carbon nanotubes to explore the behavior of monolayers in the 1D limit, by adsorbing molecules either on the surface of an individual tube or in the grooves between two or more bundled tubes. The density of molecules as a function p and T can be deduced from the shift in natural vibrational frequency, detected via the capacitance to an underlying gate electrode.
Planar graphite –
2D fluids and solids
Single nanotube –
crossover from 2D to 1D
Nanotube bundle –
Extreme 1D liquids
We have characterized the vibrational resonances of several suspended nanotubes and observed damping in argon gas at room temperature. The next step is to cool them and see cylindrical monolayer formation for the first time. 2 68 71
argon pressure (mbar)
frequency (MHz) 40
120
drive frequency (MHz)
dc gate voltage (tension)
-10
+10
grayscale = vibration
amplitude
T = 300 K
nanotube Pt
2 mm
trench
p, T
Gate electrode d s
resonance
fades out
resonance