The synthesis "holey carpet" of CNT by using CVD method

E. Shawat, C.L. Pint, D. Nessim
Bar-Ilan university, IL

Keywords: reservoir, carbon nanotubes, CVD, Mo, catalayst

Summary:

Controlling the density carpets remains a challenge for the synthesis of aligned carbon nanotubes (CNTs). In our previous work we propose the design of a catalyst stack composed of a thin oxide support under which resides a catalyst reservoir to replenish the catalyst during CNT synthesis. Specifically, we design samples with e-beam evaporated Fe thin film catalyst on Al2O3 underlayer and additional thin Mo sublayer beneath the alumina underlayer. With the inclusion of the Mo sublayer, we synthesized CNT carpets that were up to 400µm tall and with uniform spacing between the carbon nanotubes. High-resolution imaging confirms the presence of holes spacing inside the vertically aligned. in our previous work atomic force microscopy (AFM) carried out on samples using comparable process conditions showed a bimodal formation of Fe catalysts for the samples with the Fe sublayer, and subsequent etching experiments emphasize the presence of pinholes in the alumina support which enables the redistribution of Fe catalyst from the sublayer to the overlayer, thus we can assume the same for the Mo sublayer. This result is significant as it elucidates further mechanistic aspects of CNT growth and provides a new technique to tune the density of CNT carpets.