Prevention of Si-contaminated nanocone formation during plasma enhanced CVD growth of carbon nanotubes

• Published in: Carbon (New York) Vol. 43; no. 4; pp. 835 - 840
• Main Authors: Kim, Dong-Wook, Chen, L.-H., AuBuchon, J.F., Chen, I.-C., Jeong, Soo-Hwan, Yoo, In K., Jin, S.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 2005; Elsevier Science
• Subjects: A. Carbon nanotubes; B. Chemical vapor deposition; C. Scanning electron microscopy, Transmission electron microscopy; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Materials science; Physics; Specific materials; B. Chemical vapor deposition; C. Scanning electron microscopy, Transmission electron microscopy; A. Carbon nanotubes; CVD; Carbon nanotubes; Plasma; Growth
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2004.11.018

We investigated the growth behavior and morphology of vertically aligned carbon nanotubes (CNTs) on silicon (Si) substrates by direct current (DC) plasma enhanced chemical vapor deposition (PECVD). We found that plasma etching and precipitation of the Si substrate material significantly modified the morphology and chemistry of the synthesized CNTs, often resulting in the formation of tapered-diameter nanocones containing Si. Either low bias voltage (∼500 V) or deposition of a protective layer (tungsten or titanium film with 10–200 nm thickness) on the Si surface suppressed the unwanted Si etching during growth and enabled us to obtain cylindrical CNTs with minimal Si-related defects. We also demonstrated that a gate electrode, surrounding a CNT in a traditional field emitter structure, could be utilized as a protection layer to allow growth of a CNT with desirable high aspect ratio by preventing the nanocone formation.