Investigation of substrate temperature and cooling method on the properties of amorphous carbon films by hot-filament CVD with acetylene

A study based on the structural, optical and electrical properties of amorphous carbon (a-C) films by hot-filament chemical vapor deposition (HFCVD) with acetylene is reported. Effect of substrate temperature ranging from 450 °C to 850 °C and cooling method including hydrogen, argon and furnace cooling was mainly investigated. The structural transitions from a-C to nanocrystalline graphite (nc-G) and from nc-G to graphite were observed by raising substrate temperature. Hydrogen content in a-C films decreased sharply as the temperature increased from 450 °C to 550 °C, which corresponded to the high growth rate and large roughness at 550 °C. The influence of cooling method on properties of a-C films was attributed to different compressive stress produced by the volume shrinkage during cooling process. The films grown at 850 °C followed by hydrogen cooling exhibited the best performance with an optical gap of 1.2 eV, a mobility of 3.18 cm2/(V·s) and an electrical resistivity of 7.79 × 10−3 Ω·cm, which were comparable to the reported properties of a-C films by other methods. These results indicated that HFCVD is a good method to synthesize high quality a-C films.

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