Transferable thin films of pristine carbon nanotubes

We describe here a simple and low-cost method to prepare ultra-thin, homogeneous, and transferable films of pristine carbon nanotubes (CNTs). The highly efficient chemical vapor deposition (CVD) growth method involves silica supported catalysts and alcohol vapor as gaseous carbon source. By varying the amount of catalysts, the thickness of synthesized films can be easily tuned from 20 nm (sub-monolayer) to 150 nm in a controlled fashion. High-resolution transmission electron microscopy (HRTEM) revealed that the films are composed primarily of single-walled and a small fraction of double-walled CNTs. A nonlinear relationship between film conductivity and thickness was observed. Our sub-monolayer ( 20 nm) film, which is noticeably thinner than conductive CNT films synthesized using other methods (typically > 50 nm and up to 100 microm), shows the highest conductivity of 400 mho x cm(-1) with 90% transparency in the visible range and close to 100% transparency in the infrared range. This ultra-thin film can also be transferred carrier-film free to a wide range of substrates including low-cost plastics for flexible electronics. Compared to CNT films prepared by filtration techniques, our films demonstrated superior stability against mechanical bending.