Fabrication and properties of TiO$_{2}$ cluster films

Recently much interest has been directed toward nanostructured pure and doped semiconductors for their interesting dielectric, optical and magnetic properties and potential applications in spintronic devices. In this study a gas-condensation cluster-deposition system was used to make cluster-assembled films. Ti and TiO$_{2 }$targets were used to prepare Ti and TiO$_{2}$ cluster assembled films. The Ti and TiO$_{2 }$clusters were examined by TEM to determine their size and size distribution. Films were scanned by AFM to see their surface morphology and examined by XRD to see their structural evolution with annealing temperature and annealing time. TEM revealed that the sizes of the Ti and TiO$_{2}$ clusters are 9 and 20 nm respectively. After annealing at 400 $^{o}$C for an hour in oxygen, the Ti cluster films transform into pure polycrystalline rutile, which has a high dielectric constant, whereas the TiO$_{2 }$cluster films remain a mixture of anatase and some rutile even after 900$^{ o}$C annealing. The optical, magnetic and dielectric properties of the films will also be discussed. This work is sponsored by NSF-MRSEC,ONR and NCMN.