The approach of transferring CNT thin films from one surface to another via a soft lithography technique suffers from limited ability to achieve good adhesion of the CNT films to the transferred substrate and imprecise alignment of the CNT patterns. A transfer technique that can be scaled to large area with high throughput processing at low temperature is being reported in this paper, demonstrating a scalable means to create aligned CNT thin film patterns on both rigid and flexible substrates.
Pint CL, Xu YQ, Moghazy S, Cherukuri T, Alvarez NT, Haroz EH, Mahzooni S, Doorn SK, Kono J, Pasquali M, and Hague RH
Lithographic patterning of wafer-scale traces of Al2O3 (10 nm thick) followed by 0.5 nm of Fe catalyst.
Growth is then conducted by water-assisted chemical vapor deposition (CVD) in which the height and diameter of the SWNTs are determined by the pattern width and reaction exposure time.
This is followed by a post-growth H2/H2O vapor etch which effectively releases the chemical bond between the catalyst layer and the SWNTs, therefore the interface is controlled by the weaker van der Waals interactions.
Transfer is achieved by toppling the SWNT patterns over via a process in which the transfer substrate is drawn across the surface of the growth substrate, essentially toppling the patterned arrays.
A key advantage of the transfer process is the removal of catalyst from the as-grown nanotubes during the vapor etch process, thereby eliminating possible contaminants from subsequent process steps, as well as allowing reuse of the original patterned catalyst template.
Chemical Vapor Deposition