Fine-tuning control on CNT diameter distribution, length and density using thermal CVD growth at atmospheric pressure: an in-depth analysis on the role of flow rate and flow duration of acetylene (C2H2) gas

Nishant Tripathi,S. S. Islam,Prabhash Mishra,Harsh Harsh

doi:10.1007/s13204-013-0288-8

Nishant Tripathi, S. S. Islam + Show 2 more

https://doi.org/10.1007/s13204-013-0288-8

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Journal: Applied nanoscience	Publication Date: Jan 12, 2014
Citations: 47	License type: CC BY 2.0

Affiliation: Jamia Millia Islamia

Abstract

An optimization control has been demonstrated to obtain carbon nanotubes having specific diameter distribution, length, homogeneity, and yield during its growth by thermal chemical vapor deposition technique under atmospheric pressure. Carbon nanotubes (CNTs) were grown on silicon wafer where a predeposition of iron catalyst of 2 nm thickness was made by sputtering. The growth was conducted under two variable parameters, i.e., flow rate and flow duration. Argon and hydrogen mixture was used for pretreatment of catalyst and as etching gas, and acetylene as a carbon precursor. In-depth analysis shows that increase in flow rate from 10 to 50 sccm resulted in increase in the concentration of amorphous carbon, CNTs diameter range and decrease in length, we found best result at 20 sccm flow rate of acetylene gas. On the other hand, as we varied flow duration from 6 to 14 min, with keeping flow rate of acetylene 20 sccm constant, dense homogeneous growth of horizontal CNTs network plus an increase in length and diameter range were observed. An optimization of flow rate and flow duration is presented here to obtain a selective diameter distribution and length as expected by this growth technique. Atomic force microscopy, field emission scanning electron microscopy and Raman spectroscopy were used to investigate the samples’ morphologies in support of the observations made.

Highlights

Since the discovery of carbon nanotubes (CNTs) (Iijima et al 1991), a huge interest has been generated all over the world because of its high mobility, large current-carrying capacities, very high mechanical strength and host of other potential applications in the area of electronics, medical sciences and many other fields
In-depth analysis shows that increase in flow rate from 10 to 50 sccm resulted in increase in the concentration of amorphous carbon, Carbon nanotubes (CNTs) diameter range and decrease in length, we found best result at 20 sccm flow rate of acetylene gas
We present a profound study about the effect of different flow rate and flow duration of the carbon precursor gas (C2H2) on the growth of CNTs by thermal CVD method

Summary

Introduction

Since the discovery of carbon nanotubes (CNTs) (Iijima et al 1991), a huge interest has been generated all over the world because of its high mobility, large current-carrying capacities, very high mechanical strength and host of other potential applications in the area of electronics, medical sciences and many other fields. 2003; Zobir et al 2012; Lou et al 2004; Song et al 2009; Dai 2002; Atthipalli et al 2011) using carbon source gas has become a promising one for CNTs growth It has following merits: lower preparation temperatures, better techniques for large-scale CNTs production, easy to design a CVD system, easy to control the parameter and having much chances to grow aligned, horizontal and selective growth of CNTs, these are very useful in electronic device applications. We have successfully achieved the capability to fine-tune the length, diameter distribution, surface density, yield, and quality of CNTs by varying flow rate and flow duration of acetylene gas. The effect of flow rate and flow duration of C2H2 gas on the growth of CNTs, samples were investigated by high resolution scanning electron microscope (FESEM, NOVA NANOSEM 450) and Micro-Raman spectrometer with 488 nm Ar? laser (LabRAM HR800, JY)

Result and discussion

Conclusion