AVS 58th Annual International Symposium and Exhibition
    Thin Film Division Wednesday Sessions
       Session TF1+EM-WeM

Paper TF1+EM-WeM11
Titanicone Molecular Layer Deposition Using TiCl4 and Sugar Alcohols and Porous TiO2 Films Produced by Annealing

Wednesday, November 2, 2011, 11:20 am, Room 110

Session: ALD/MLD: Hybrid Organic Films
Presenter: Robert A. Hall, University of Colorado, Boulder
Authors: R.A. Hall, University of Colorado, Boulder
A.I. Abdulagatov, University of Colorado, Boulder
S.M. George, University of Colorado, Boulder
Correspondent: Click to Email
Metalcone molecular layer deposition (MLD) can be performed using metal precursors and organic diols or triols. The first metalcone MLD films were the alucones and zincones grown using trimethylaluminum and diethylzinc, respectively, with ethylene glycol (EG). In this work, we report the growth of titanicone MLD films using TiCl4 and two sugar alcohols: EG and glycerol (GL). The titanicones may have useful photocatalytic properties and may form valuable porous TiO2 frameworks upon annealing to remove the organic constituent. Titanicone films were grown using TiCl4 and EG at temperatures between 90-135°C. Quartz crystal microbalance (QCM) measurements observed a growth rate of ~83 ng/cm2-cycle from 90 to 115°C before decreasing significantly at 135°C. X-ray reflectivity (XRR) studies obtained a growth rate of 4.5 Å/cycle with a density of 1.84 g/cm3 at 115°C. Titanicone films were grown using TiCl4 and GL at higher temperatures between 130-210°C. The GL is believed to lead to more cross-linking that stabilizes the MLD film. QCM measurements observed growth rates that varied slightly with temperature from 49 ng/cm2-cycle at 130°C to 34 ng/cm2-cycle at 210°C. XRR studies yielded a growth rate of 2.2 Å/cycle at 150°C. QCM measurements revealed that the surface chemistry for titanicone MLD was self-limiting. XRR studies indicated that the titanicone films were stable in air. The titanicone films were absorptive in the ultraviolet and consistent with an optical bandgap of ~3.5 eV. Annealing the titanicone films removed the carbon component and yielded porous TiO2 films. Ultraviolet exposures also appear to be able to produce porous TiO2 films. The ability to deposit conformal porous TiO2 films on high surface area substrates could produce “super” high surface area substrates. These substrates may serve as TiO2 scaffolds for dye-sensitized solar cells or photocatalytic membranes.