Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455, USA.
Nanotechnology. 2011 Apr 22;22(16):165601. doi: 10.1088/0957-4484/22/16/165601. Epub 2011 Mar 11.
The fabrication and characterization of single-walled carbon nanotube (SWCNT) composite thin film micropatterns and suspended beams prepared by lithography-compatible layer-by-layer (LbL) nano-self-assembly are demonstrated. Negatively charged SWCNTs are assembled with a positively charged polydiallyldimethylammonium chloride, and the composite thin film is patterned by oxygen plasma etching with a masking layer of photoresist, resulting in a feature size of 2 µm. Furthermore, the SWCNT nanocomposite stripe pattern with a metal clamp on both ends is 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 the deflection of about 50 nm. A high Young's modulus is found in a range of 500-800 GPa based on the characterization of a fixed-fixed beam using nanoindentation. This value is much higher than those of the other CNT-polymer composites reported due to organization of structures by self-assembly and higher loading of CNTs. The stiff CNT-polymer composite thin film micropattern and suspended beam have potential applications to novel physical sensors, nanoelectromechanical switches, other M/NEMS devices, etc.
通过光刻兼容的层层（LbL）纳米自组装制备单壁碳纳米管（SWCNT）复合薄膜微图案和悬梁，并对其进行了制备和特性研究。带负电荷的 SWCNTs 与带正电荷的聚二烯丙基二甲基氯化铵组装在一起，然后通过带有光刻胶掩模层的氧等离子体刻蚀对复合薄膜进行图案化，得到 2 µm 的特征尺寸。此外，通过在氢氟酸蒸气中刻蚀二氧化硅牺牲层，释放出带有金属夹的 SWCNT 纳米复合材料条带图案。I-V 测量表明，释放后 SWCNT 纳米复合材料薄膜的电阻降低了 23%，这可能是由于 CNTs 的重新取向导致约 50nm 的挠度所致。通过使用纳米压痕对固定-固定梁进行特性研究，发现杨氏模量在 500-800 GPa 范围内。由于自组装和更高的 CNT 负载使结构有序化，这个值远高于其他报道的 CNT-聚合物复合材料的值。这种刚性 CNT-聚合物复合薄膜微图案和悬梁在新型物理传感器、纳米机电开关、其他 M/NEMS 器件等方面具有潜在的应用。
