1. A 10-a editie a Seminarului National de nanostiinta si nanotehnologie 18 mai 2011 Biblioteca Academiei Romane The versatility of catalytic LCVD technique to grow carbon nanotubes 1 st Step: the preparation of the substrate 2 nd Step: synthesis of nanotubes by LCVD Sample Ar window sccm C2H2 sccm SF6 sccm Ar (in mixture) sccm Pressure mbarr PL W Time min CNT lenght 1D1000305-80 33-4 µm 1F10003010-80 3300-400 nm 1E10003010580 3200 nm 10A10003015580 3> 500 µm There is a compromises between SF6 and Ar mixture SF6/Ar MIXTURE INFLUENCES LASER POWER AND PRESSURE INFLUENCES By increasing PL increase the length of CNT and sometime increase also the thickness By increasing pressure increase the length of CNT Sample Ar window sccm C2H2 sccm SF6 sccm Ar (in mixture) sccm Pressure mbarr PL W Time min CNT lenght 10A10003015580 3> 500 µm 1-710003015580603110 µm 1-94003015540 380 µm 1-18400301554030330 µm 1-11400155-40 340 µm 1-19400155-4030340 µm 1-12400105-40 360 µm 1-14400105-403032-3 µm Laser beam 12 mm Sample Ar window sccm C2H2 sccm NH3 sccm Pressure mbarr Temperature o C PL W Time min 10-710003090100900272 10-610003090100430132 10-110003090450430282 10-2100030180100430152 10-3100030180450430202 10-4100030270100430252 10-8100030270450430282 Laser beam 1 mm The catalytic LCVD offers the advantage of high versatility and control since it separates the catalyst preparation from the catalytic growth of nanotubes. The possibility of controlling the size of the laser spot on the substrate allows to heat the substrate very locally and to produce CNTs for various applications. The high versatility as concerning the catalyst nature and preparation. A cold wall reactor in which the CO 2 -laser radiation is heating both the silicon substrate and the gas phase. High deposition rates, that are favorable for scale-up production of CNTs LCVD was recently used to fabricate lines of CNTs and to control the orientation of the tubes by use of an electric field Laser polarization could significantly influence the selective growth of CNTs. Compared with the post-growth manipulation, the in situ growth is more suitable for large-scale device fabrication. >500 m In order to avoid CNT damage, the temperature was adjusted from 900 o C to about 430 o C (by acting on the laser power) At lower pressure CNT are oriented in the direction of gas flow 800-900 C400-500 C 100 mbarr 450 mbarr On the catalytic growth of CNT by LCVD technique: 1.NH3 additive gas is more efficient than SF6: unwanted carbon deposits are not formed unwanted carbon deposits are not formed the mean diameters are much thinner the mean diameters are much thinner 2. The formation temperature is relatively low. Perspective Iuliana Morjan 1,2, Ion Morjan 2, Rodica Alexandrescu 2, Catalin Luculescu 2, Eugeniu Vasile 3, Monica Scarisoreanu 2, Anca Barbut 2 1 IMT-Bucharest, 126A, Erou Iancu Nicolae street, 077190, PO-BOX 38-160, 023573, Bucharest, ROMANIA 2 National Institute for Lasers, Plasma and Radiation Physics, 409 Atomistilor St, P.O. Box MG-36, 077125, Bucharest, Romania 3 METAV-R&D, 31 C.A. Rosetti St., 020011 Bucharest, Romania Acknowledgement: some of the results were obtained in the frame of the Project POSDRU/89/1.5/S/6370