Filling of carbon nanotube forests grown by atmospheric pressure PECVD

This presentation examines aspects of the growth and filling of carbon nanotube forests. Composites containing CNTs are predicted to inherit the best properties of the CNTs (strength, toughness, resistivity, thermal conductivity). However, good dispersion of the CNTs is vitally important in fabricating composites with features approaching those theoretically predicted. Significant deterioration of the composite properties has been shown to occur when the CNTs agglomerate rather than being uniformly dispersed. Filling as-grown CNT forests with various materials can result in a composite with excellent CNT dispersion. Furthermore, the growth of forests is becoming very popular for both single-wall and multi-wall CNTs of high quality. LPCVD is a very good technique to fill the CNT forests with a wide variety of materials, so we have studied the filling process on various forests. Filling begins by coating the individual CNTs with the (inorganic) material. Large coating thicknesses bridge the gap between adjacent CNTs and result in a continuous composite layer. Polysilicon/CNT composites fabricated under conditions that yield good step coverage were found to exhibit hardness similar to that of bulk polysilicon and high fracture toughness but also high sheet resistance. Voids deep inside films over 25 microns thick remain a significant issue.