Iron films were deposited onto QCM crystals from ferrocene, bis(cyclopentadienyl)Fe(II) (FeCp2) using plasma electrons as reducing agents. The deposition system setup and the experimental procedures are described elsewhere. Briefly, a custom-made stainless-steel vacuum chamber with a base pressure of 6 Pa was used with a titanium hollow cathode plasma source (with water-cooling system) mounted in the top lid of the vacuum chamber (Fig. ). The QCM sensor was used instead of a substrate holder and was positioned downstream from the plasma source (Fig. ) with a diagonal distance of 7 cm between the QCM electrode and the hollow cathode orifice. This to allow the precursors to reach the QCM and adsorb at the surface prior to entering the main plasma bulk to minimize plasma chemical decomposition of the metal precursors as much as possible. Argon gas (140 sccm) and a DC power supply (5-20 W) were used to generate the plasma at a pressure of 33 Pa.