K and Au Bicatalyst Assisted Growth of Carbon Nanocoils from Acetylene: Effect of Deposition Parameters on Field Emission Properties
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- 作者：Tsung-Yu Tsou ; Chi-Young Lee ; Hsin-Tien Chiu
- 刊名：ACS Applied Materials & Interfaces
- 出版年：2012
- 出版时间：December 26, 2012
- 年：2012
- 卷：4
- 期：12
- 页码：6505-6511
- 全文大小：443K
- 年卷期：v.4,no.12(December 26, 2012)
- ISSN：1944-8252
文摘
We demonstrated the growth of carbon nanocoils (CNCs) via chemical vapor deposition (CVD) using Au and K metals as the catalysts to assist the thermal decomposition of C2H2. Typical CNCs (wire diameter: 50鈥?0 nm, coil diameter: 110鈥?40 nm, pitch: 100鈥?00 nm, tens of micrometers), identified as amorphous coiled carbon fibers by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were grown at proper combinations of reaction parameters. Au nanoparticles (NPs), identified by energy dispersion X-ray spectroscopy (EDX) and electron diffraction (ED), were located at the tips of the CNCs. The observations suggested that a tip-growth mechanism involving the Au NPs as the nucleation sites was in operation. In the reaction, the liquid-phase K metal assisted the decomposition of C2H2 by lowering the reaction temperature. We propose that acetylide and hydride intermediates were formed in the reaction. Further decomposition of the acetylide intermediates generated solid-phase carbon to grow the CNCs. Effects of varying the reaction conditions on the CNC growth were investigated. On the basis of the results, a Au and K bicatalyst enhanced tip-growth vapor鈥搇iquid鈥搒olid (VLS) mechanism was proposed to rationalize the CNC formation process. Electron field emission (EFE) characteristics of the CNCs were studied. The best EFE result showed a turn-on field (Eto) of 3.78 V/渭m and a field enhancement factor (尾) of 1852. In addition, the current density (J) was as high as 43 mA/cm2 at 6.87 V/渭m. The data suggest that the CNCs could be employed for field emission device applications.