Unidirectional Growth of Single-Walled Carbon Nanotubes

Abstract

Unidirectional growth of single-walled carbon nanotubes (SWNTs) was achieved using the patterned Co-Mo salt catalyst on the r-plane sapphire substrate. This is in marked contrast with the SWNTs grown on an a-plane sapphire and ST-cut quartz, on which the SWNTs grew bidirectionally. This new growth mode is not dependent on the gas flow and attributed to the asymmetric surface atomic arrangement of the sapphire surface.

Investigations on the effects of CoOx to MoOx ratio and CoOx–MoOx loading on methane decomposition into carbon nanotubes

“…In our previous findings, MoO x was found to be an effective promoter for CoO x used for producing CNTs of better morphology and yield [15]. Particularly relevant to the current work, the significance of Co-Mo catalysts supported on various oxides for the synthesis of CNTs has also been reported by other research groups lately [16][17][18][19][20][21][22]. Co-Mo catalysts have effectively been used to grow single-walled carbon nanotubes from carbon monoxide [20,21] or alcohol [22].…”

Guided Growth of Horizontal Single-Wall Carbon Nanotubes on M-Plane Sapphire

“…As shown in Table 1, for A-plane and R-plane the main alignment directions are identical for CNTs, 11,22,23 ZnO NWs, 15,16 GaN NWs, 17 and SnO 2 NWs. 18 For the C-plane, which has higher symmetry, the 6-fold symmetric alignment is the same for ZnO 16 and GaN 17 NWs; however, no alignment was reported for CNTs.…”

Techniques of aligning carbon nanotubes

“…Alignment of as-grown CNTs is commonly evaluated using atomic force microscopy (AFM) [34], scanning tunneling microscopy (STM) [35] or scanning electron microscopy (SEM) [36][37][38]. Transmission electron microscopy (TEM) [39,40] is less suitable because it requires relatively complex sample preparation, which can modify the CNT arrangement.…”

“…Most popular metals used as a catalyst are Fe, Ni, Co, Mo or they allows [25]. The metal catalyst nanoparticles are often produced on the substrate using indirect processes, such as reduction of metal oxides or salts [25,[36][37][38]. The particle density and structure can be controlled by pat- terned (or masked) deposition of the metal, annealing, or by plasma etching of a metal layer.…”

“…A more delicate solution is growing the nanotubes not normal to the substrate but along its surface. Low density of the catalyst results in bending down the CNTs, and their alignment is achieved using the atomic steps on specially oriented sapphire [36][37][38] (Fig. 5) or trenched silicon [59,60] substrates.…”