Selective growth of carbon nanotubes on silicon protrusions

Abstract

Selective growth of carbon nanotubes (CNTs) to required positions is a matter of importance for an application to electron sources for field emitter arrays. Although some techniques have been proposed concerning the selective growth of carbon nanotubes, they have complex processes and difficulties in reliability and controllability. We have developed the selective CNT growth technique, which consists of fabrication of pyramid-shaped protrusion arrays on silicon (Si) substrate by a liftoff process, selective deposition of metal catalyst film on the vertexes of the protrusions, and growth of the CNTs on the metal catalyst by chemical vapor deposition (CVD). Here we report the detailed growth characteristics of CNTs selectively grown by thermal CVD (TCVD) on vertexes of pyramid-shaped protrusions fabricated on Si substrate. The growth of CNTs by TCVD gave long, randomly oriented and dispersed CNT growth, which was completely different from growth regimes given by plasma enhanced CVD (PECVD), i.e., vertically aligned and bundled growth. The array of the CNTs grown by TCVD gave better field emission characteristics than that with the CNTs grown by PECVD. That was presumably because the CNTs grown by TCVD gave longer and more dispersive CNT growth than PECVD and consequently gave higher field enhancement on the CNTs. It is also shown that the single growth of the CNT is successfully performed using this process.