Low temperature plasma carbon nanotubes growth on patterned catalyst (original) (raw)
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Journal of Applied Physics, 2001
Direct-current plasma-enhanced chemical vapor deposition ͑CVD͒ with mixtures of acetylene and ammonia was optimized to synthesize aligned carbon nanotubes ͑CNTs͒ on Co-or Ni-covered W wires with regard to wire temperature, wire diameter, gas pressure, and sample bias. A phase diagram of CNT growth was established experimentally in this optimization process. It was revealed by transmission electron microscopy that Co-catalyzed CNTs encapsulated a Co carbide nanoparticle at their tip, disagreeing with a previous report that Co particles were located at the base of CNTs CVD grown on Co-covered Si substrates ͓C. Bower et al., Appl. Phys. Lett. 77, 2767 ͑2000͔͒. This leads to the conclusion that the formation mechanism of aligned CNTs depends significantly on the catalyst support material as well as the catalyst material itself. Since the sample bias strongly affected the morphology of CNTs, the selective supply of positive ions to CNT tips was possibly responsible for the alignment of growing CNTs.
Plasma Chemistry and Plasma Processing, 2008
A mixture of acetylene, hydrogen and ammonia (C 2 H 2 /H 2 /NH 3 ) is used to produce carbon nanotubes (CNTs) by a plasma-enhanced catalytic chemical vapor deposition process either without (PE CCVD) or with hot filaments-assistance (PE HF CCVD). A mathematical model based on Chemkin computer package is used for analyzing specific conditions of nanotube synthesis. Simulations are compared with optical emission spectroscopy (OES) measurements. Morphological and structural investigations on the grown carbon nanostructures are also performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was shown that the significant change in the density and the morphology of the CNTs grown in the presence of NH 3 could be mainly explained by the gas phase formation of CN and HCN. Both species display a high etching activity, whereas the species C, CH, CH 2 , CH 2 (S), C 2 and C 2 H are expected to be the most probable carbon nanotube precursors.
Diamond and Related Materials, 2003
The growth behaviour of carbon nanotubes (CNTs), produced by radio-frequency plasma enhanced chemical vapour deposition, is studied here as a function of a CH yAr ratio and Ni catalyst layer thickness. The composition of the plasma mixture was 4 observed as being crucial for the morphology of the nanotubes, indicating a transition from a random to a more uniform orientation, when argon is added to the plasma atmosphere. Scanning tunnelling microscopy shows, as a result of the argon dilution, the formation of a defective structure (i.e. pentagons) at the tip of vertically aligned CNTs while hexagonal atomic arrangement was detected on the sidewall of randomly oriented CNTs deposited by pure methane. The electronic structure of CNTs was then investigated by C 1s' photoemission spectroscopy. The results show a shift of the overall spectral to the higherbinding-energy side, indicating the formation of metallic aligned tubes when argon is added to the plasma atmosphere. Experimental results are applied to develop a coherent picture of the relationship between the deposition parameters and the microstructural features, as well as to check the relationship of the electronic properties predicted for nanotubes with the plasma chemical composition. ᮊ
Journal of Applied Physics, 2001
The growth of vertically aligned carbon nanotubes using a direct current plasma enhanced chemical vapor deposition system is reported. The growth properties are studied as a function of the Ni catalyst layer thickness, bias voltage, deposition temperature, C 2 H 2 :NH 3 ratio, and pressure. It was found that the diameter, growth rate, and areal density of the nanotubes are controlled by the initial thickness of the catalyst layer. The alignment of the nanotubes depends on the electric field. Our results indicate that the growth occurs by diffusion of carbon through the Ni catalyst particle, which rides on the top of the growing tube.
Japanese Journal of Applied Physics, 2009
Carbon nanotubes (CNTs) have been grown by surface-wave plasma-enhanced chemical vapor deposition (CVD) using size-classified Co nanoparticles at low temperatures. A mesh grid is used in the remote plasma-enhanced CVD system for the suppression of ion bombardment damage from plasma. The control of the electric field distribution using a mesh grid with a narrower opening is effective for the CNT growth. Multiwalled CNTs are obtained at a low temperature of 400 C under low ion-density conditions. No significant difference in the microscopic structure of the CNTs grown at temperatures between 400 and 500 C is observed.
Patterned growth of carbon nanotubes obtained by high density plasma chemical vapor deposition
Journal of Physics: Conference Series, 2015
Patterned growth of carbon nanotubes by chemical vapor deposition represents an assembly approach to place and orient nanotubes at a stage as early as when they are synthesized. In this work, the carbon nanotubes were obtained at room temperature by High Density Plasmas Chemical Vapor Deposition (HDPCVD) system. This CVD system uses a new concept of plasma generation, where a planar coil coupled to an RF system for plasma generation was used with an electrostatic shield for plasma densification. In this mode, high density plasmas are obtained. We also report the patterned growth of carbon nanotubes on full 4-in Si wafers, using pure methane plasmas and iron as precursor material (seed). Photolithography processes were used to pattern the regions on the silicon wafers. The carbon nanotubes were characterized by micro-Raman spectroscopy, the spectra showed very singlewalled carbon nanotubes axial vibration modes around 1590 cm-1 and radial breathing modes (RBM) around 120-400 cm-1 , confirming that high quality of the carbon nanotubes obtained in this work. The carbon nanotubes were analyzed by atomic force microscopy and scanning electron microscopy too. The results showed that is possible obtain high-aligned carbon nanotubes with patterned growth on a silicon wafer with high reproducibility and control.