Electrical conduction of carbon nanotube forests through sub-nanometric films of alumina

Abstract

We report both the growth of carbon nanotube forests and electrical conduction on W, Ti, and TiN substrates coated with an ultra-thin Al2O3 support layer. Varying the Al2O3 thickness, a good electrical contact and high nanotube density is possible for a 0.5 nm Al2O3 layer as such an ultra-thin film allows tunnelling. X-ray photoelectron spectroscopy shows that, when using these non-continuous Al2O3 films, Fe catalyst diffuses into the conducting substrates, eventually causing growth to stop. Forests grown on ultra-thin Al2O3 are potentially useful for applications as interconnects, supercapacitors, and heat spreaders.

Single-step CVD growth of high-density carbon nanotube forests on metallic Ti coatings through catalyst engineering

“…The derived resistances are ~1 kΩ for the CNT-Au contacts and ~1.5 kΩ for the CNT-CNT contacts. Although the overall electrical resistance is similar to or up to 10 times higher than those CNTs grown on other conductive substrates [19,33,41,42], it is still very promising if considering the high resistance of the annealed substrates. This implies nanotubes would have a fairly good contact with the Ti coating and Ti carbides may be formed during the growth of nanotubes, preventing the Ti coating from oxidation to some extent.…”

“…In order to reduce the contact resistance between the nanotube and the support, it is essential to grow CNT forests directly on metal supports without the assistance of any insulating oxide coatings. Recently, encouraging progress has been made [18,[31][32][33]. Esconjauregui et al succeeded in growing multi-walled CNT (MWCNT) forests (4×10 11 cm -2 ) on conductive substrates by tuning the nominal thickness of the Al 2 O 3 support down to 0.5 nm, which allows a good electrical contact through tunnelling [33].…”

“…Recently, encouraging progress has been made [18,[31][32][33]. Esconjauregui et al succeeded in growing multi-walled CNT (MWCNT) forests (4×10 11 cm -2 ) on conductive substrates by tuning the nominal thickness of the Al 2 O 3 support down to 0.5 nm, which allows a good electrical contact through tunnelling [33]. Yamazaki et al reported the growth of almost closely packed MWCNT forests (1×10 12 cm -2 ) on 10 nm TaN by a multi-step growth method using plasma-assisted CVD [31].…”

Increased carbon nanotube area density after catalyst generation from cobalt disilicide using a cyclic reactive ion etching approach

“…[11][12][13] This is because CNTs can carry a high current density up to $10 9 AÁcm À2 , which is over two orders of magnitude higher than for Cu. For use of CNTs in contact applications, it is necessary to grow high density CNTs on conductive substrates such as Cu, TiN, or TaN, [12][13][14][15][16] or on silicides. Silicides such as NiSi, CoSi 2 , TiSi 2 , and PtSi have been widely used as the contact materials in the semiconductor industry [17][18][19][20][21][22] due to their controllable forming process, low resistivity, good adhesion to silicon, and thermal stability.…”

Carbon nanotube forests as top electrode in electroacoustic resonators

“…Several metals and compounds (e.g. W, Ir, Mo, TiSiN, doped-Si) [27][28][29][30] allow direct forest growth, and so would reduce the contact resistance while the electrode weight is still low.…”