Croissance localisée de nanotubes de carbone aux échelles micrométrique et nanométrique

Abstract : The realization of carbon nanotubes (CNT) based nanotechnological devices rests primarily on the controlled integration of the CNTs on chips. We developed this theme by choosing, rather than handling of synthesized CNTs, the approach of localised CNT growth by CCVD (Catalytic Chemical Vapor Deposition) under H2-CH4 gaz mixture. Our work enabled us to selectively synthesize CNTs starting from well-defined catalytic sites, on silicon substrates. Our study related to the synthesis of NTC from deposits of catalytic cobalt nanoparticles (NP) which were prepared according to three distinct ways: in situ NP formation on a supporting oxide matrix by selective reduction of the oxide solution solid Mg0,95Co0,05O made by sol-gel route ; NP preformed by chemical route, deposited directly on a SiO2/Si substrate; NP formed by the annealing of thin Co metal layer also deposited on SiO2/Si substrate. We showed that CCVD under pure methane or H2-CH4 mixture, with a heating step under inert gas, leads to CNT formation from 850°C, starting from unstructured catalytic deposits. In particular, the choice of the adequate catalytic system allows (1) to produce dense films of NTC (approximately 1 CNTs/µm²); (2) to promote the formation of single-walled or double-walled CNTs, whose diameter generally lies between 0.8 and 4 nm, and the length about a few tens of µm. Techniques of patterning were developed with the aim of locating the catalytic NP deposits. Microcontact-printing (soft-lithography technique) of a liquid catalytic precursor (sol or cobalt-NP suspension) seems an adequate technique for the production of micrometric catalytic patterns (1 - 100 µm). However, the electron beam lithography remains the privileged tool to locate catalytic nanometric patterns (down to 50 nm) with respect to predefined structures on silicon substrates. Our work demonstrates the adequation of localised growth for the production of CNT patterns with a relative control of the CNT surface density, compatibl e with the formation of interconnections between adjacent patterns. The ultimate dimension of the produced patterns varies between 50 nm and 100 µm, depending on the nature of catalyst and the employed patterning technique. Our study does not highlight the clear influence of the organization of the catalytic patterns on the orientation of the CNTs, which mainly remains random on the surface of the SiO2/Si substrates, whatever the nature of the catalyst used.
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Micro et nanotechnologies/Microélectronique. Université Paul Sabatier - Toulouse III, 2006. Français
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Stéphane Casimirius. Croissance localisée de nanotubes de carbone aux échelles micrométrique et nanométrique. Micro et nanotechnologies/Microélectronique. Université Paul Sabatier - Toulouse III, 2006. Français. <tel-00136052>



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