Transmission electron microscopy studies of atomic layer deposition TiO2 films grown on silicon

Transmission electron microscopy techniques have been used to characterise atomic layer deposition TiO2 films grown on silicon substrates after RCA and HF treatment. The influence of deposition temperature (250-350 degreesC) and substrate type on the film microstructure have been determined. The major influence of substrate type is to control nucleation of crystallisation. HF treated silicon, which was devoid of the native oxide layer, promoted a crystalline, island growth mode. The nucleation of crystalline particles at the onset of deposition resulted in films with very fine grain sizes ( approximate to 20 nm). The RCA treated silicon, which was coated with amorphous native oxide, caused the growth of an initially amorphous TiO2 film, which crystallised once a critical film thickness had been exceeded. The major influence of temperature on the films grown on RCA treated silicon was to control nucleation of crystallisation within the amorphous layers, resulting in grain size refinement at higher deposition temperatures. Under the processing conditions used, other than the transient amorphous films formed on RCA treated silicon, anatase was the only phase formed. No evidence for preferred orientation was found. (C) 2003 Elsevier Science B.V. All rights reserved.