NASA connects down under for growth of carbon nanotubes
Coatings of nanotube forests developed by NASA are the blackest materials ever measured, which has great importance for many scientific uses. The NASA team has worked for several years to make their formulation black over a wide spectral range, has improved robustness and the number of materials to which the nantoubes can be applied. With some assistance from Australia, NASA is further developing carbon nanotube technology for use on parts with complex shapes.
Principal Investigator John Hagopian and co-investigator Vivek Dwivedi of the NASA Goddard Space Flight Center are using Atomic Layer Deposition (ALD) to deposit layered thin films suitable for carbon nanotube growth on intricate parts.
To gain the highest sensitivity and consistent measurements, carbon nanotubes must be evenly deposited across the surface of the detection component. This requires a highly uniform foundation layer, commonly a film of nanoparticles or iron oxide, to support growth of the carbon nanotubes. This is difficult to achieve using deposition techniques such as sputtering or evaporation since corners or crevasses are left uncoated or there is a large variation in thickness of the coating. ALD is one technique that can coat all surfaces of an intricate object in a highly controlled and uniform layer.
The MCN was engaged through Science Exchange (www.scienceexchange.com) to develop and apply an ALD process for thin film coatings in NASA instrument components. Science Exchange is an online community marketplace where scientific service providers can offer their services. Through the ANFF linkage to Science Exchange, the MCN was identified as a preferred site for collaboration due to its two ALD systems and dedicated technical support.
The NASA researchers worked in collaboration with MCN’s operating expert in ALD, Lachlan Hyde, to perform a number of iterations for ALD growth of iron thin films. Characterization by Hyde using MCN’s spectroscopic variable angle ellipsometer allowed the film thickness and uniformity to be optimised on test wafers. According to Hyde, “the iron films that we deposited initially were not as uniform as other coatings we have worked with, so we needed a methodical development process to achieve the outcomes that NASA needed for the next step.”
The NASA team were provided with development samples, their intricate part containing an ALD grown film, as well as a detailed report on the process, including development recipes and analysis of ALD film growth.
MCN's Lachlan Hyde working on the ALD system
Hagopian and Dwivedi have since conducted trial production of carbon nanotubes on these wafers at NASA.
“We have successfully performed growth on two development samples with an ALD iron catalyst from MCN and the nanotubes have properties very similar to those grown using electron beam deposited catalysts” said Hagopian.
“The growth of nanotubes directly onto an ALD catalyst is a new and emerging technique. The samples we have grown to date are flat in shape as we have several additional technical challenges to solve in terms of uniformly exposing the surface to the carbon-bearing gas during nanotube growth. I am extremely impressed with the quality of the work that ANFF performed and the professionalism of everyone involved. Both their ALD process development and characterization capabilities are world class. We intend to continue our collaboration and look for additional opportunities to leverage their capabilities to increase our speed of technology development.”
4th July 2013