Optical in situ characterisation of carbon nanotube growth

Abstract

Post-print of a peer-reviewed article published by Inderscience Publishers.

In situstudies of growth of carbon nanotubes on a local metal microheater

“…A constant flow of 300 sccm hydrogen and 500 sccm argon was supplied during the whole process. Ethylene, introduced downstream of the carrier gases, was used as carbon feedstock and the flow rate was varied between 6 and 100 sccm (6,12,30,100 sccm). The gas was supplied via a 2m long Swagelok tube with an inner diameter of 3mm (internal volume 15 cm 3 ).…”

“…The carbon feedstock was introduced to the growth chamber only after a stable voltage drop across the heater was reached for a given current. The introduction of the hydrocarbon gas is accompanied by a noticeable jump in the voltage drop, indicating a higher resistivity and correspondingly greater heating power [12]. The working current through the heater was varied in the range 36-42 mA, which resulted in initial temperatures (immediately prior to hydrocarbon injection) from 630 °C to 690 °C.…”

“…The working current through the heater was varied in the range 36-42 mA, which resulted in initial temperatures (immediately prior to hydrocarbon injection) from 630 °C to 690 °C. The temperature was determined from analysis of the grey-body radiation from the heater [9,12] using the same spectrometer which was used for Raman spectra acquisition. Previous studies showed that the temperature increase on introduction of the hydrocarbon gas was typically ca.…”

“…We have followed a slightly different approach in the use of simple metallic microheaters, patterned directly on silicon chips, that can be easily fabricated using standard lithography [2,8,9,12]. These have the advantages of simplicity and a direct means of electrically contacting the grown structures but the disadvantage of complicating the temperature determination since the properties of the heater change on exposure to hydrocarbon gas at elevated temperatures [12]. In this paper we use metal microheaters to investigate carbon nanotube growth using iron catalyst particles and ethylene as hydrocarbon feedstock.…”

“…The use of the local microheater technique allows us to combine a small heater chamber with a conventional micro-Raman spectrometer and optical microscopy for CNT growth visualisation [9], [12]. Previously, in situ Raman spectroscopy was performed with conventional oven CVD growth [22] [23] for direct measurements of the evolution of the G-peak intensity with growth time and correspondingly, an estimation of the initial growth rate and timescale for catalyst degradation.…”