Effects of ammonia/methane ratios on the properties of hermetically carbon-coated optical fibers prepared by thermal chemical vapor deposition

• Main Authors: Yu-Xian Liu, 劉煜賢
• Other Authors: 薛顯宗
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/74049541135223641007

碩士 === 國立中興大學 === 材料科學與工程學系所 === 98 === The effects of NH3/(CH4+NH3+Ar) ratios on the properties of carbon coating of hermetically carbon-coated optical fibers prepared by thermal chemical vapor deposition are investigated. The deposition parameters are selected as follows. The CH4/(CH4+ NH3+Ar) ratio is in the range between 67.5 and 87.5 %; the temperature is set from 930 to 1000℃; the working pressure is arranged between 525 and 725 torr, and the residence time is ranging from 1.33 to 2.32 s. The deposition rate, microstructure, surface property, and electrical property of carbon coatings are measured. The low-temperature surface morphology of carbon-coated optical fibers is observed. Experimental results indicate that the deposition rate increases with increasing the CH4/(CH4+ NH3+Ar) ratio, deposition temperature, working pressure, and residence time. The activation energy (= 538 kJ/mole) of carbon deposition from methane was shown to correlate to the activation energy of methane dissociation. The deposition rate is proportional to about ninth-order of partial pressure of methane. When CH4 content at 72.5%, the nano-crystallite size (Lc) and amount of the sp2 C have maximum value and the resistivity shows a minimum value. Additionally, results from the water-repellency and low-temperature surface morphology studied indicate that using ammonia (NH3) as adding precursor gases is good for producing hermetical optical fiber coatings when the carbon coating thickness is greater than 99 nm.