Growth of carbon nanotubes in the microchannels of glass substrates

Carbon nanotubes (CNTs) were grown in soda-lime glass microchannels using microwave plasma enhanced chemical vapor deposition and an Fe–Si thin film catalyst. It was found that CNT growth in the microchannels is different from that on flat substrates. The growth length is proportional to t0.5 for the CNTs grown in microchannels; whereas the length is proportional to t1.5 for the CNTs grown on flat substrates. The former is attributed a diffusion-controlled growth mechanism where the depth of the microchannel serves a diffusion boundary layer; while the later is attributed to a reaction-control growth mechanism where the growth rate increases linearly with the methane concentration used. From Raman analysis, the CNTs grown in microchannels at low methane concentrations seem to have better crystalline structure than that grown on flat substrates. The opposite is true at high methane concentrations. The cross point is at a methane concentration of 18%.