Formation of ultra-thin ceramic TiO2 films by the Langmuir-Blodgett technique - a two-dimensional sol-gel process at the air-water interface

Different molecular titanium alkoxides were investigated as precursors for the synthesis of thin to ultra-thin TiO2 ceramic films. The films were prep ared by the Langmuir-Blodgett technique. Therefore, the precursor was disso lved in CHCl3 and subsequently spread on water, aqueous acetic acid and aqu eous acetylacetone as the subphase. Hydrolysis of the titanium alkoxides, n amely Ti(OR)(4-x)(OR')(x) with x = 0 (R = n-C4H9 or n-C9H19) and x = 2 (R = n-C4H9 and R' = 2, 4 pentanedionate) and [(RO)(2)Ti-O-](n) with R = n-C4H9 was performed at the air-water interface. This reaction can be considered as a two-dimensional sol-gel-process. The surface-pressure-area (pi-A) isot herms as well as the influence of the molecular structure of the precursor on the morphology of the resulting condensation products (gels) are discuss ed. Pyrolysis of the transferred gels under oxygen atmosphere up to 700 deg rees C gives the desired TiO2-layers. (C) 1999 Elsevier Science S.A. All ri ghts reserved.