Nanolithographic control of carbon nanotube synthesis

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Title: Nanolithographic control of carbon nanotube synthesis
Author: Huitink, David Ryan
Abstract: A method offering precise control over the synthesis conditions to obtain carbon nanotube (CNT ) samples of a single chirality (metallic or semi -conducting ) is presented . Using this nanolithographic method of catalyst deposition , the location of CNT growth is also precisely defined . This technique obviates three significant hurdles that are preventing the exploitation of CNT in micro - and nano -devices . Microelectronic applications (e .g . , interconnects , CNT gates , etc . ) require precisely defined locations and spatial density , as well as precisely defined chirality for the synthesized CNT . Conventional CVD synthesis techniques typically yield a mixture of CNT (semi -conducting and metallic types ) that grow at random locations on a substrate in high number density , which leads to extreme difficulty in application integration . Dip Pen Nanolithography (DPN ) techniques were used to deposit the catalysts at precisely defined locations on a substrate and to precisely control the catalyst composition as well as the size of the patterned catalyst . After deposition of catalysts , a low temperature Chemical Vapor Deposition (CVD ) process at atmospheric pressure was used to synthesize CNT . Various types of catalysts (Ni , Co , Fe , Pd , Pt , and Rh ) were deposited in the form of metal salt solutions or nano -particle solutions . Various characterization studies before and after CVD synthesis of CNT at the location of the deposited catalysts showed that the CNT were of a single chirality (metallic or semiconducting ) as well as a single diameter (with a very narrow range of variability ) . Additionally , X -ray photoelectron spectroscopy (XPS ) was used to characterize the deposited samples before and after the CVD , as was lateral force microscopy (LFM ) for determination of the successful deposition of the catalyst material immediately after DPN as well as following the CVD synthesis of the samples . The diameter of the CNT determines the chirality . The diameter of the CNT measured by TEM was found to be consistent with the chirality measurements obtained from Raman Spectroscopy for the different samples . Hence , the results showed that CNT samples of a single chirality can be obtained by this technique . The results show that the chirality of the synthesized CNT can be controlled by changing the synthesis conditions (e .g . , size of the catalyst patterns , composition of the catalysts , temperature of CVD , gas flow rates , etc . ) .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2539
Date: 2009-05-15

Citation

Nanolithographic control of carbon nanotube synthesis. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2539 .

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