Thin films of crystalline titania with different grain sizes and porosities
were prepared by dip-coating on Si (100) substrates starting from a sol-gel
process. Three synthesis procedures were developed and compared, using
acetylacetone (acac, with HCI) and acetic acid (HOAc) as modifying agents or
directly using hydrochloric acid as catalyst. The structural evolution of
the films was characterized by Glazing Angle X-ray Diffraction (XRD),
Spectroscopic Ellipsometry and Atomic Force Microscopy (AFM). Anatase phase
was observed on all of the films calcined at 440° C. The grain sizes and
crystallinity generally increased with calcination temperature. Thin films
obtained from acac- and HOAc-modified titanium sols had fine grains (50–80
nm) and less porosity (<10%) after calcination at 1000° C. Thin films
derived from the sol catalyzed directly with acid had the largest grains
(90–130 nm), higher crystallinity and greater porosity (17%).