Reflectance and Transmittance of Multi-Walled Carbon Nanotube Forests

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T.C. Shen


Black surfaces are useful as black-body sources for optical calibration, stray light suppression in optical systems, and as absorbers for radiometric devices. It is believed that carbon nanotube forest (CNTF) films are the blackest materials to have been examined. Several studies have investigated their reflectance and absorption but resulting data has variability. Mizuno et al. has reported that single-walled carbon nanotube (CNT) forests provide a nearly constant reflectance and transmittance over a wide spectral range from UV (200 nm) to far IR (200 'm) on silicon oxide[1] while Arcos et al. have shown an increasing reflectance and transmittance over the near IR spectral region.[2] As such, the correlation between optical properties with CNTF morphologies was the focus of this study. In this presentation, I will discuss our integrating sphere study of total reflectance and transmittance of CNT forests of different heights and densities on different substrates (quartz, Al/Si, Nb/Si). We find that surface chemistry plays an important role in CNT forest morphology and greater forest height may not reduce reflectance if the density is not properly adjusted. Modeling the CNTF as a good conductor allows us to study the absorption coefficient of these samples to test the forest height independence and the densitys influence on this parameter. [1] Mizuno et al. Proc. Nat. Acad. Sci. 106, 6044 (2009). [2] T. de los Arcos, P. Oelhafen, D. Mathys, Nanotech. 18, 26 (2007)

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