Effects of under CNT metallization layers on carbon nanotubes growth

Carbon nanotubes (CNTs) were grown on a Ni catalyst layer with four different types of under-CNT-metallization layers, namely SiO₂, Al, Cu and Cr, using hot filament chemical vapor deposition (HFCVD). The morphology and microstructure of the CNT films were analyzed by scanning electron microscopy (SEM) and Raman spectrometer. It was found that the level of interaction between the Ni catalyst layer and under-CNT-metallization layer has significant effects on carbon nanotubes growing characteristics. It was observed that carbon nanotubes grown on SiO₂ under-CNT-metallization layer recorded the highest density and smallest diameter. When Cu or Cr under-CNT-metallization layers were employed, high density and larger diameter nanotubes were obtained. No carbon nanotubes were found on samples with Al under-CNT-metallization layer under similar growth conditions. These findings add significant reference values for selection under CNT metallization layers suitable for carbon nanotube interconnect applications.