Growth of high-density vertically aligned arrays of carbon nanotubes by plasma-assisted catalyst pretreatment

Abstract

A plasma-assisted thermal pretreatment of catalyst films ͑Ni, Co, or Fe͒ greatly facilitates the direct growth of high-density vertically aligned arrays of small diameter carbon nanotubes ͑CNTs͒ on conductive TiN by purely thermal chemical vapor deposition. Purely thermal catalyst pretreatment gives limited or no growth. The plasma-assisted pretreatment promotes a stronger catalyst-support interaction, which reduces catalyst mobility and hence stabilizes smaller catalyst particles with a higher number density.

Superhydrophobic Carbon Nanotube Electrode Produces a Near‐Symmetrical Alternating Current from Photosynthetic Protein‐Based Photoelectrochemical Cells

“…Fabrication of the MWCNT electrode involved the preparation of a CoSi 2 surface to act as a base layer, and as part of that process a 20 nm thick TiN fi lm was used as a capping layer to prevent oxidation of Co during silicidation. [ 34 ] Both of these materials can act as electrodes, [ 35 ] and have work functions in the same region as MWCNTs ( − 4.62 eV for CoSi 2 [ 36 , 37 ] and − 4.8 eV for TiN [ 38 ] compared to − 4.95 eV for MWCNTs [ 39 ] (Figure 1 b)). However both CoSi 2 and TiN are markedly more hydrophilic than MWCNTs, yielding contact angles with a droplet of water of 53.2 ° and 64.3 ° , respectively ( Figure S2; Supporting Information), intermediate between previously measured values for a Pt electrode (93.8 ° ) [ 26 ] and for the highly hydrophilic FTO-glass front electrode (18.7 ° ).…”

Growth of vertically-aligned carbon nanotube forests on conductive cobalt disilicide support

“…[8][9][10][11][12][13][14] There are many fewer reports of nanotubes grown on metal supports. 4,[15][16][17][18][19][20][21] It has proved very difficult to obtain similar growth of dense, vertically-aligned nanotube forests on conducting support layers. Some of the previous reports were on metals not compatible with microelectronics 16 and some gave relatively low nanotube densities or disordered horizontal networks or "spaghetti."…”

In-situ study of growth of carbon nanotube forests on conductive CoSi2 support

“…TiN and TaN are widely used in microelectronics and CNTs have been found to grow on these supports. 25,28 However, the nitride surfaces are easily oxidized. 28,29 This suggests silicides as an alternative due to their high stability.…”

“…The higher surface energy inhibits the catalyst film from transforming itself into a series of nanoparticles. [22][23][24][25][26] In addition, the metallic support must retain its conductivity/functionality during the CVD processes at elevated temperatures in the presence of reactive gases, but metals are often reactive themselves under such conditions. 27 This means that supports must possess both favorable surface energetics for high density nanoparticle formation and a chemical stability against carbide-formation (from carbon source gas) or oxidation (from residual oxygen or water).…”