Half-centimeter-high mats of vertically aligned single-walled carbon nanotubes were grown at 600 degrees C by point-arc microwave plasma chemical vapor deposition. The mats were produced from 0.5 nm of an Fe catalyst layer, thus showing one of the highest catalytic yields of similar to 10(5) times. The growth process shows a lack of poisoning of the catalyst, in contrast to other reports. The experimental results confirm that the growth rate is ultimately limited by the gas phase diffusion of hydrocarbon radicals.