Controlling Direction of Growth of Carbon Nanotubes on Patterned SiO₂Substrate

Abstract

A new technique to preferentially control the direction of the growth of single-walled carbon nanotubes (SWNTs) is proposed. SWNTs are grown by the thermal chemical vapor deposition process on patterned SiO 2 substrates with line and space grooves of the order of submicrometers. SWNTs grow along the lower corner of the grooves and are oriented along the direction of the grooves. Further, we propose two modes of SWNT growth along the grooves on the SiO 2 substrates: the stick at first mode and the vibration in air mode.

Growth of horizontally aligned single-walled carbon nanotubes on anisotropically etched silicon substrate

“…28 For stepped crystal substrates, the combined forces of surface adhesion from the substrate-carbon nanotube interaction and the aerodynamic drag caused by the gas flow induced bending of carbon nanotubes. Similarly in our case, the alignment of nanotubes 25 occurs at the time when the length of the grown nanotubes drops at its own weight during growth and aligns its length along the trench. However, there is a limitation to the misalignment of the trenches and gas flow direction for such mechanism to occur.…”

“…By combining both the proposed alignment mechanisms, this paper presents a new insight of aligning SWNTs with higher density and higher degree of alignment compared to 2 the previously reported results. [16][17][18][19][20]24,25 Moreover, we will show that both gas-flow assisted and "trench-assisted" alignment contributed to the improvement of density and degree of alignment. Lastly, parameters like temperature, gas flow rate, gas flow direction, and trench widths were varied in 5 order to investigate scalability.…”

“…Moreover, the degree of alignment was improved by the presence of trenches. The combination of gas-flow induced and trench-induced alignment enhanced the total 25 SWNT density. We have proposed that the trench profile and temperature can affect the degree of alignment.…”

“…However, SWNTs escaped due to the inconsistent shape of the trench giving a lesser degree of alignment compared to the 55 gas-flow directed alignment. 24,25 Our previous results suggested that trench structure is essential for improving the degree of SWNT alignment.…”

Combinatorial catalyst approach for high-density growth of horizontally aligned single-walled carbon nanotubes on sapphire

“…Direct growth of horizontally aligned SWCNTs has been achieved by using electric field or laminar gas flow during the chemical vapor deposition (CVD) growth [14][15][16][17]. Also, the surface-guided growth has been proposed on single-crystal substrates [18][19][20][21][22][23][24][25][26][27] and trenched SiO 2 /Si wafers [28][29][30]. Among these, the lattice-oriented mechanism observed on the single-crystal substrates, such as sapphire (-Al 2 O 3 ) [19][20][21][22] and quartz (-SiO 2 ) [23][24][25][26][27], has attracted a great interest because the substrates can give high-density SWCNT array with high degree of alignment.…”