Browsing by Subject "Chemical Vapor Deposition"
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Item Nanolithographic control of carbon nanotube synthesis(2009-05-15) Huitink, David RyanA 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.).Item Novel organometallic precursors for the Chemical Vapor Deposition of metal thin films(2010-08) Rivers, Joseph Henry; Jones, Richard A., 1954-; Cowley, Alan H.; Holliday, Bradley J.; Magnus, Philip D.; Ekerdt, John G.With the growing demand for miniaturization of devices and for new materials with useful properties, the use of Chemical Vapor Deposition (CVD) for the manufacture of thin films is receiving growing attention. The synthesis of potentially volatile metal complexes and investigation of their use as CVD precursors is an important part of this process. The research presented addresses several major areas of this process, (i) the identification and synthesis of ligands which can impart volatility to a metal complex, (ii) the synthesis, characterization, and assessment of volatility of metal complexes containing these ligands, and (iii) the full materials characterization of thin films grown with these complexes. The use of trimethylphosphine, bis(trifluoromethyl)pyrazolate, and bis(trifluoromethyl)pyrrolyl ligands have been successfully used to synthesize volatile new complexes of cobalt, rhodium, and nickel, some of which show promise for use as potential CVD precursors.