Growth of aligned carbon nanotubes by biasing during growth

Abstract

Well aligned multiwalled carbon nanotube (CNT) growth was achieved by positively biasing the substrate during growth. Growth was performed in a flowing mixture of 7% CH4 in Ar onto Co covered Si held at 800 °C with and without the presence of an electric field. High resolution scanning electron microscopy shows that the tube alignment occurs only when a positive bias is applied to the substrate whereas no aligned growth occurs under a negative bias and no tube growth is observed, under the presently applied conditions, with no field. This finding may open up the possibility of realizing cold electron emitting devices based on CNTs with a large electric field enhancement. In particular, it may be possible to utilize the same gate which is needed to turn the device on also to obtain field assisted aligned carbon nanotube growth into the desired regions. Alternatively, due to the fact that no CNTs grow under the conditions of this experiment without bias, selected area biasing may permit selected area growth of vertically aligned carbon nanotubes, a process that may find many applications.

The Properties and Application of Carbon Nanostructures

“…DLC films can be deposited using DC plasma chemical vapor deposition, radio frequency magnetron sputtering or ion beam-based methods. DLC (polycrystalline diamond) needs high temperatures to be deposited [56]. Amorphous carbon can be prepared at low temperatures by different techniques, but its physical, chemical and mechanical properties depend on the deposition conditions, mainly on the temperature and hydrogen content [57].…”

Techniques of aligning carbon nanotubes

“…Millimeter-tall forests can be produced of aligned CNTs standing on the substrate [46,47]. Not only high density of nanotubes, but also application of electric field normal to the substrate during the growth aligns the nanotubes [25,48]. Changing the direction and strength of the electric field allows to control the nanotube orientation and structure [25].…”

Controlled growth of carbon nanotubes on electrodes under different bias polarity

“…3,9 E-field induced aligned growth of CNTs [10][11][12][13][14][15][16] has been investigated and applied in fabrication of ordered CNT arrays. However, mechanisms suggested to explain the E-field alignment effects are still controversial.…”