Bidirectional Evanescent and Transmitted Light Scattering Profiles of CVD synthesized Carbon Nanotubes (CNTs) for Ex-situ Characterization of Structural Formation

Keywords:
bidirectional elastic light scattering, Evanescent wave, Carbon Nanotubes (CNTs), characterization, concentration, height, and structural formation

Abstract:
In this paper we studied bidirectional elastic light scattering intensity profiles of CVD synthesized CNTs grown on a glass substrate with varying process variables. Angular vertical-vertical polarized intensity(Ivv) profiles between 20 deg and 135 deg of observation angle were measured with the optical system and were related with structural formation of CNTs . The Ivv – scattering measurements were taken in both evanescent wave(EW) and transmitted wave(TW) regimes at the wavelength of 515 nm.
Effects of the process variables on structural formation parameters (height and concentration) of CNTs on bidirectional scattering profiles were measured. SEM pictures of surface and cross section of CNT layers grown on surface of quartz furnace were taken to measure height and to calculate surface concentration of the CNT layer. The heights and the concentrations with varying process variables are compared with bidirectional scattering intensity profiles.Our results indicate that it is possible to monitor height and concentration from bidirectional scattering intensity profiles and most favorable observation angle range to monitor the process variables are 30-50 deg and 10-25 deg in TW and EW regimes respectively. It is also observed that EW scattering profiles is more sensitive at the early stage of the CVD process while TW scattering is better for structural characterization of middle stage of CVD process. Figure 1 shows how CNT surface area concentrations affect scattering profiles at EW and TW regimes.

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Nanotech 2006 Conference Program Abstract