Surface morphology examination of sol-gel deposited TiO2 films

Abstract

Thin films of TiO2 were deposited by spin-coating onto both single-point diamond machined (SPDM) disks and mechanically polished disks of aluminum. A titanium alkoxide sol-gel precursor was used and films were heat treated after deposition to remove organic components. This work is being undertaken to analyse the nature of the surface morphology produced by spin-coating, and to examine how the surface morphology can be modified. Detailed analysis of the surface morphology of the films was carried out using atomic force microscopy (AFM). The uncoated surfaces of the SPDM samples show cutting marks characteristics of the single-point diamond machining process, while these have largely disappeared on the coated surfaces. The coatings show some regions where flow lines are apparent, probably arising from the spinning process, but are otherwise quite featureless, indicating good surface coverage in the spinning process. Line and area scans of the coated surfaces were used to measure the surface roughness. An analysis of measured roughness as a function of the area of measurement indicates that the measured roughness increases with the area of the measurement. This applies to both line and area scans. Roughness measurements over macroscopic lenghts were also carried out with a stylus profilometer and these results are compared with the AFM measurements. Line scans of the surface profile of the materials show long wavelength surface features in some of the samples which are attributed to the diamond machining process.