We report a complete switching of catalyst particle location from the base to the tip of carbon nanotubes when grown on microscale bimetallic scrolls by simply varying the growth temperature from 400 to 450 °C. The complete switching of catalyst particle location occurs in the very narrow temperature window of 50 °C. This is attributed to the miscible and reactive properties of the bimetallic layer with the substrate. The study suggests that the switching can be manipulated by supplying silicon from the substrate by reduction in silicon dioxide to the bimetallic layer.