Metal Oxoclusters as Molecular Building Blocks for the Development of Nanostructured Inorganic\u2013Organic Hybrid Thin Films

Silica-based inorganic\u2013organic hybrid thin \ufb01lms embedding the organically modi\ufb01ed oxohafnium clusters (Hf4O2(OMc)12, OMc=OC(O)\u2013C(CH3)=CH2) were obtained by photo-activated free radical copolymerisation of the methacrylate groups of the cluster with those of the pre-hydrolysed (methacryloxypropyl)trimethoxysilane (MAPTMS, (CH2=C(CH3)C(O)O)(CH2)3Si(OCH3)3). By this route, a covalent anchoring of the cluster to the forming silica network was achieved. Samples characterized by two different Si=Hf compositions (18:1, 5:1) were prepared. The surface and in-depth composition of the thin \ufb01lms were investigated through Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). XPS depth pro\ufb01les performed on the thin layers evidenced a homogenous in depth distribution of the hafnium guest species within the whole silica \ufb01lms and sharp \ufb01lm-substrate interfaces. Broad band dielectric spectroscopy (BDS) measurements permitted to investigate the electric response of the obtained \ufb01lms in the frequency and temperature range of 40 Hz \u2013 1 MHz and 0\u2013160\ub0C