Suspended carbon nanotube nanocomposite beams with a high mechanical strength vialayer-by-layer nano-self-assembly

Abstract

The fabrication and characterization of single-walled carbon nanotube(SWCNT) composite thin film micropatterns and suspended beams prepared bylithography-compatible layer-by-layer (LbL) nano-self-assembly are demonstrated.Negatively charged SWCNTs are assembled with a positively chargedpolydiallyldimethylammonium chloride, and the composite thin film is patterned by oxygenplasma etching with a masking layer of photoresist, resulting in a feature size of2 µm. Furthermore, the SWCNT nanocomposite stripe pattern with a metal clamp on both endsis released by etching a sacrificial layer of silicon dioxide in the hydrofluoric acid vapor.I–V measurement reveals that the resistance of SWCNT nanocomposite film decreases by 23%upon release, presumably due to the effect of reorientation of CNTs caused by thedeflection of about 50 nm. A high Young’s modulus is found in a range of 500–800 GPabased on the characterization of a fixed–fixed beam using nanoindentation. This value ismuch higher than those of the other CNT–polymer composites reported due toorganization of structures by self-assembly and higher loading of CNTs. The stiffCNT–polymer composite thin film micropattern and suspended beam have potentialapplications to novel physical sensors, nanoelectromechanical switches, other M/NEMSdevices, etc.