Plasma-enhanced chemical vapor deposition of carbon nanotubes using alcohol vapor
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1057-II05-10
Plasma-enhanced chemical vapor deposition of carbon nanotubes using alcohol vapor Atsushi Okita1, Yoshiyuki Suda1, Masayuki Maekawa1, Junichi Takayama1, Akinori Oda2, Hirotake Sugawara1, and Yosuke Sakai1 1 Laboratory of Integrated Material Processings, Graduate School of Information Science and Technology, Hokkaido Univ., N14 W9, Kita-ku, Sapporo, 060-0814, Japan 2 Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555, Japan ABSTRACT We have successfully grown carbon nanotubes (CNTs) by alcohol plasma-enhanced chemical vapor deposition (PECVD). When 0.01 wt% ferrocene was added to alcohol, vertically-aligned CNTs could be grown using RF (= 13.56 MHz) plasma at 650ºC. In contrast, no CNTs were obtained by pure alcohol PECVD. To understand the plasma properties for CNT growth, especially plasma species containing a gas phase of alcohol plasma, we analyzed the plasma using optical emission spectroscopy (OES) and quadrupole mass spectrometry (QMS). From the OES measurement, one could identify the emission peaks from the excitation states of CHO, CO, C2, O2, H, CH+, and H2O+, while the QMS measurement also showed the existence of CO, H2O, and CxHy (x≥2, y≥2). It is considered that such plasma species affect CNT growth by changing the oxidation state of the catalyst or by adjusting the amount of precursor species in the plasma. Comparing this PECVD experiment with thermal alcohol CVD (without plasma), only PECVD can be used to grow CNTs under the reported experimental conditions. It is considered that thermal alcohol CVD requires more energy to grow CNTs because 650ºC is a little lower than the temperature required for CNT growth. These results indicate that in alcohol plasma, the active species produced by decomposition and recombination reactions have a possibility to promote/suppress CNT growth depending on the process conditions. INTRODUCTION Recently, carbon nanotubes (CNTs) have attracted much interest due to their unique properties; e.g. high chemical stability, mechanical strength and current density. Based on these properties, our group has focused on the application of CNTs as nano-scale interconnections in large-scale integrated circuits [1]. To realize such an application, highly controllable processes and highly dense CNT growth with lower temperature operation (
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