Metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) structures fabricated by magnetron sputtering deposition of insulating hydrogenated amorphous carbon are analyzed by measuring their current-voltage characteristics in order to find the conduction mechanism. For MIM structures, the linearity of the logarithmic dependencies between current density and electric field intensity (log J-Iog E) for higher fields indicate a space charge limited current (SCLC) conduction mechanism. The calculated values of the effective mobility are in agreement with other literature results. For MIS structures, the power-law dependence between current and voltage also indicate a space-charge limited currents based conduction mechanism. (c) 2006 Elsevier B.V. All rights reserved.