Deposition of Nanotubes and Nanotube Composites Using Matrix-Assisted Pulsed Laser Evaporation

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Deposition of Nanotubes and Nanotube Composites using Matrix-Assisted Pulsed Laser Evaporation P. K. Wu', J. Fitz-Gerald 2, A. Pique2 , D.B. Chrisey2 , and R.A. McGill2 ' Southern Oregon University, Ashland, OR. Naval Research Laboratory, Code 6370, Washington D.C. 20375

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Using the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) process developed at the Naval Research Laboratory, carbon nanotubes and carbon nanotube composite thin films have been successfully fabricated. This process involves dissolving or suspending the film material in a volatile solvent, freezing the mixture to create a solid target, and using a low fluence pulsed laser to evaporate the target for deposition inside a vacuum system. The collective action of the evaporating solvent desorbs the polymer/nanotube composite from the target. The volatile solvent is then pumped away leaving the film material on the substrate. By using this technique singlewall-nanotubes (SWN) have been transferred from the target to the substrate. The SWN sustain no observable damage during the deposition process. Using SWN in combination with polymers as the target material, SWN/polystyrene and SWN/polyethylene glycol composite films were made. These films can be deposited on a variety of substrates, e.g., Si, glass, plastic, and metal, using the same target and deposition conditions. SEM micrographs show that the SWN were uniformly distributed in the film. Using a simple contact mask, SWN composite films 20 um diameter patterns can be produced. I. Introduction Nanotubes were first identified by Sumjo lijima.' Since their discovery, new fabrication 2-4 and purification techniques have enhanced the production of single-wall-nanotubes (SWN). SWN with lengths up to a few hundred ýim can be produced. SWN are interesting materials in many ways. They can be either metallic or semiconducting, depending on its chiral structure and diameter. 569 SWN not only have exceptionally high modulus, > Ix 012 Pa, 7"8 but are also flexible and strong. These remarkable properties make SWN a subject of intense materials research. The present work illustrates how SWN/polymer composite thin film can be fabricated using Matrix-Assisted Pulsed-Laser Evaporation (MAPLE). 10.-2 We will demonstrate that MAPLE is suitable for fabricating a variety of SWN/polymer composites. This is technologically important because SWN/polymer composite is one way to fabricate materials with custom properties for specific applications. For example, the mechanical toughness for a polymer can be improved by forming a polymer composite with SWN. Because of the stability and inertness of SWN, SWN/polymer is potentially useful as biomaterials in applications such as requiring special structure or in novel drug delivery. Furthermore, forming a composite with SWN can alter the dielectric constant of a polymer; thus improving the polymer's electrical characteristics for applications such as interconnects. In short, the ability to make polymeric composites with SWN permits the alteration of materials properties, i.e., me

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