Aligned carbon nanotubes and composites for electrical interconnect and thermal interface materials are provided. In one preferred embodiment, an aligned carbon nanotube device comprises a substrate and a plurality of carbon nanotubes having a substantially vertical profile. The substantially vertical carbon nanotubes are coupled to the substrate. In another preferred embodiment, a carbon nanotube production method comprises depositing a catalyst on a substrate and flowing at least one of argon, hydrogen, and ethylene over the catalyst for a predetermined time at a predetermined temperature to produce a carbon nanotube. This production method enables production of high purity carbon nanotubes and also enables precise placement of carbon nanotubes on a substrate. Other embodiments are also claimed and described.