Optical Properties of Evolutionary Grown Layers of Carbon Nanowalls Analyzed by Spectroscopic Ellipsometry

Carbon nanowalls (CNWs), vertically standing graphene sheets, grown by the radical injection plasma-enhanced chemical vapor deposition system were analyzed by spectroscopic ellipsometry. The refractive indexes ($n$), extinction coefficients ($k$), and optical band gaps ($E_{\text{g}}$) of evolutiona...

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Bibliographic Details
Published inJapanese Journal of Applied Physics Vol. 49; no. 6; pp. 060220 - 060220-3
Main Authors Kawai, Shinji, Kondo, Shingo, Takeuchi, Wakana, Kondo, Hiroki, Hiramatsu, Mineo, Hori, Masaru
Format Journal Article
LanguageEnglish
Published The Japan Society of Applied Physics 01.06.2010
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Summary:Carbon nanowalls (CNWs), vertically standing graphene sheets, grown by the radical injection plasma-enhanced chemical vapor deposition system were analyzed by spectroscopic ellipsometry. The refractive indexes ($n$), extinction coefficients ($k$), and optical band gaps ($E_{\text{g}}$) of evolutionary growth layers were evaluated using the Tauc--Lorentz model with the effective medium approximation. It was observed that an amorphous carbon interfacial layer with $n$ of 1.9--2.0 was formed prior to the growth of CNWs with $n$ of 1.2--1.5. Moreover, the imaginary parts of complex dielectric functions analyzed using the Tauc--Lorentz model indicate the possibility that the CNWs have semiconducting features.
Bibliography:Top-view SEM images of samples grown for (a) 0.5, (b) 2, and (c) 5 min. Raman spectra of interfacial layer grown for 0.5 min and CNWs grown for 2 and 5 min. The Raman spectrum of the Si substrate is also indicated for comparison. (a) Film thickness, (b) refractive index, and (c) extinction coefficient of the interfacial layer and CNWs evaluated by spectroscopic ellipsometry, as a function of growth time. Film thicknesses measured from cross-sectional SEM images are also indicated in (a) for comparison. Real and (b) imaginary parts of complex dielectric functions of interfacial layer grown for 0.5 min and CNWs grown for 2 and 5 min.
ISSN:0021-4922
1347-4065
DOI:10.1143/JJAP.49.060220