Methods and apparatus for controlling a catalytic layer deposition process are provided. A feed stream comprising a carbon source is provided to a catalyst layer. An asymmetrical alternating current is applied to the catalyst layer. A polarization impedance of the catalyst layer is monitored. The polarization impedance can be controlled by varying the asymmetrical alternating current. The controlling of the polarization impedance provides control over the structure and amount of carbon particles deposited on the catalyst layer. The carbon particles may be in the form of nanotubes, fullerenes, and/or nanoparticles.