Surface sol-gel synthesis of ultrathin titanium and tantalum oxide films

TiO₂, Ta₂O₅, and mixed TiO₂, Ta₂O₅ ultrathin films were grown layer-by-layer using a surface sol-gel deposition technique. The technique allows one to prepare smooth films of mixed composition with Ångstrom-level control of thickness. The thickness increases per adsorption/hydrolysis cycle were 4.5, 2.1, and 2.5 Å, respectively, for TiO₂, Ta₂O₅and mixed TiO₂/ Ta₂O₅ (1.6:1) films. By combining X-ray diffraction and ellipsometric analysis, it was determined that the as-deposited TiO₂ films are less dense than bulk TiO₂, and do not adhere persistently to Si/SiO₂ or Au/2-mercaptoethanol substrates. These 'green' films were annealed at 400°C to produce denser and highly adherent films. Patterning the surface by microcontact printing of siloxane polymer thin films allows one to prepare patterned sol-gel oxide thin films.