Isaac Harriman (isaacharriman2000@gmail.com)

The goal of this experiment was to better characterize the effects of gas flow rate and sample position on carbon-infiltrated carbon nanotubes (CICNTs) grown via chemical vapor deposition (CVD) on a silicon substrate. Methods: 18 batches of 3 samples each (52 samples) were prepared by CVD coating silicon wafer substrates with alumina (400nm) and iron (4nm). Standard processes were generated for creating CICNT samples, with carbon nanotube (CNT) growth at 750C and subsequent carbon infiltration at 900C. In each batch, samples were positioned linearly with samples located centrally, downstream, and upstream in the furnace. Three batches had -20% gas flows (both hydrogen and ethylene), three batches had standard gas flows, and three batches had +20% gas flows. The experiment was then repeated with hydrogen flow held constant (only the ethylene was varied). Results: At all gas flow rates for both experiments, samples that were located further forward in the tube furnace had larger CICNT diameters and increased CICNT heights. Increasing the flow rate of both gases increased the nanotube diameter on average, but the average height of the nanotubes was greatest at standard flow rates. Preliminary results from the second experiment indicated that varying only the ethylene concentration had a negligible effect on CICNT diameter. We saw clear correlations between sample position in the furnace and CICNT diameter and height. Our results also indicated that variation in hydrogen flow rate has a greater effect on nanotube growth than the ethylene flow rate.