Atomic layer deposition on bulk quantities of surfactant-modified single-walled carbon nanotubes
Journal of the American Ceramic Society, 2008, 91(3): 831-835.
Atomic layer deposition (ALD) on single-walled carbon nanotubes (SWNTs) can be achieved through physical surface modification using liquid-phase pretreatment dispersion techniques. Al2O3 ALD on nonfunctionalized SWNTs produced isolated nodule growth. Ethanol and sodium dodecylsulfate (SDS) pretreatment methods were utilized to disperse and functionalize batches of nanotube powders. Ethanol-based dispersion techniques provided hydroxylated surfaces that promoted continuous Al2O3 films on SWNT surfaces. The SDS method provided a dense nucleation site pattern that allowed for conformal Al2O3 film growth. Al2O3 ALD processes yielded growth rates of 0.13 nm/cycle, independent of the functionalization technique, at 450 K. X-ray photoelectron spectroscopy was used to quantify the composition of the films, which were amorphous as deposited. A surfactant-assisted ALD mechanism is proposed, which retains a physisorbed micelle structure as a template for the dense precursor nucleation site pattern. Liquid-phase pretreatment was found to be an efficient mechanism to overcome attractive forces associated with nanoscale particle systems, and significantly reduced the size of nanotube bundles. The successful ALD on an individual suspended nanotube in other work was extended to the bulk coating of SWNT powders. This work demonstrates significant progress toward the goal of producing commercially viable SWNT-based nanocomposite devices that incorporate bulk quantities of ALD-functionalized nanotubes.