Carbon Networks Synthesized using Microwave Plasma Enhanced Chemical Vapor Deposition
- PDF / 558,289 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 53 Downloads / 258 Views
Carbon Networks Synthesized using Microwave Plasma Enhanced Chemical Vapor Deposition D. J. Yang*, Qing Zhang, S.F. Yoon, J.Ahn, S.G. Wang, Q. Wang Microelectronics Centre, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 ABSTRACT A new carbon network is prepared using microwave plasma enhanced chemical vapor deposition(MPCVD) under the plasma of a mixture of methane, hydrogen and nitrogen at 720 o C. The Field Emission Scanning Electronic Microscopy(FESEM) images show that the carbon nanotubes are self-organized into carbon networks, which is different from the previously reported carbon nanotube ropes or nanofibers. The carbon networks are about 1 micron in diameter, more than 10 microns in length and composed of hundreds of carbon nanotubes with the diameter from 20 to 100 nm. Energy Dispersive X-Ray(EDX) results confirm that the network is carbon in nature, with a small amount of Ni which was used as catalyst.
INTRODUCTION Carbon nanotube(CNT) is one of the most promising materials for the fabrication of nanoelectronic device. Different structures of carbon nanotubes can lead to different electronic properties. Since carbon nanotube were first synthesized by Iijima in 1991[1], many kinds of methods were used to prepare carbon nanotube, including arc discharge, laser vaporization, pyrolysis and plasma enhanced chemical vapor deposition[2]. So far many kinds of morphology of carbon nanotube have been prepared, such as carbon nanotube rope, carbon nanofiber, carbon nanotube ring etc[2]. In this paper, we report the growth of carbon networks on a large area of Ni coated silicon substrate using microwave plasma chemical vapor deposition. To our knowledge, this morphology of carbon networks hasn’t been reported before.
EXPERIMENT DETAILS In our experiments, we use an AsTex microwave plasma deposition system to prepare the networks. Prior to preparation, 300 nm-thick nickel(Ni) thin film was deposited on p-type silicon(100) substrate with resistivity of 15-Ω/cm using electron beam (EB) evaporator. Then the Ni coated silicon substrates were annealed in nitrogen atmosphere at 400 ºC for 10 seconds in order to enhance the Ni adhesion to Si substrate. The annealed samples were dipped into diluted HNO3 solution for 5-10 s to crack the surface of the Ni film. This pretreatment is crucial to grow carbon networks. Carbon networks were prepared in two phases at 700 °C. In the first phase, the substrates were exposed to hydrogen plasma with a flow rate of 110 sccm, with an operation pressure of 15 torr and a microwave power of 800 W for 5 mins. In the second phase, hydrogen(H2) and methane(CH4) were introduced into the chamber with flow rate fixed at 100sccm and 10sccm . The microwave power, deposition pressure, and deposition time are 850 Z3.14.1
W, 15 torr, and 10 mins respectively. The chamber was cooled down to room temperature in vacuum condition. The substrate temperature was monitored using a thermocouple buried in the sample holder. The morphology of carbon networks
Data Loading...
