The characteristic evolution of TiO2/Al2O3 bilayer films produced by ALD: Effect of substrate type and wide range annealing temperature

Single bilayer (1BL) of TiO2/Al2O3 nanolaminate films were grown on n-Si (100) and glass substrates via Atomic Layer Deposition technique. Films were deposited using tetrakis (dimethylamino)titanium(IV), trimethylaluminum and water vapor as precursors at a reactor temperature of 200 °C. Post deposition annealing was performed on the grown nanolaminate films in a wide variable temperature range (300–1100 °C) to investigate evolution of crystal properties in detail. The films were studied with grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), and UV–Vis spectroscopy. Crystal structures of the films revealed different combinations of three phases that belong to TiO2. Phase transformations of TiO2 and Al2O3 were determined as a result of annealing. Atomic force microscopy images together with roughness values of TiO2/Al2O3 nanolaminate films showed a trend associated with crystal structure changes. Optical measurements revealed that the indirect band gap of films which produced on glass substrate decreased with respect to bulk TiO2 and prior reports. •It was revealed that the substrate materials creates differences in the structure of nanolaminate films.•TiO2/Al2O3 films present “brookite” together with anatase and rutile phase even at lower annealing temperatures.•“Brookite” phase whose production needs special conditions were determined for films using TDMAT precursor.•Band gap values of films growth on glass substrates were determined under bulk TiO2 values.