Formation Mechanism of Transparent Mo6 Metal Atom Cluster Film Prepared by Electrophoretic Deposition

Among the solution deposition techniques, electrophoretic deposition (EPD) is a fairly rapid and low cost two-step process well-known for ceramic shaping and conductive surface coating. Recently we have reported the fabrication of transparent inorganic thin film composed of octahedral molybdenum clusters and shown that the stabilization of the cluster solutions during EPD is very important to obtain high quality films. In this study, we selected the Cs2Mo6Bri8Bra6 or ((n-C4H9)4N)2Mo6Bri8Bra6 clusters compound (i = inner ligands, a = apical ligands) as precursors in a Methyl Ethyl Ketone (MEK) solution to fabricate the inorganic Mo6 cluster transparent film on a conductive indium tin oxide (ITO) glass substrate. For the first time, the mechanism for the deposition process of metal clusters is proposed based on results obtained by the combination of complementary techniques such as infrared spectroscopy, X-ray analysis and electron microscopy. The Mo6 film on the ITO glass substrate exhibiting a Br-rich layer is quickly deposited during the first stage of the EPD followed by a multilayer structure consisting of two types of cluster compounds, [Mo6Bri8Bra4(H2O)a2] and (H3O)2[Mo6Bri8Bra4(OH)a2].