Abstract: A method of making an array of vertically-aligned CNT bundles includes dispersing iron oxide nanoparticles in a solvent to form a suspension. The method further includes dipping a TiN-coated substrate in the suspension and removing to form a suspension-coated substrate. The method also involves drying the suspension-coated substrate by evaporating the solvent from the suspension-coated substrate to form a first sample. Furthermore, the method includes treating the first sample by microwave plasma under hydrogen flow at 500 degrees centigrade (° C.) to 700° C. to form a pre-treated sample followed by treating the pre-treated sample by microwave plasma under methane flow at 500° C. to 700° C. to form the vertically-aligned carbon nanotube bundles.