The characteristic evolution of TiO_2/Al_2O_3 bilayer films produced by ALD: Effect of substrate type and wide range annealing temperature

摘要

Single bilayer (1BL) of TiO_2/Al_2O_3 nanolaminate films were grown on n-Si (100) and glass substrates via Atomic Layer Deposition technique. Films were deposited using tetrakis (dime-thylamino)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 TiO_2. Phase transformations of TiO_2 and Al_2O_3 were determined as a result of annealing. Atomic force microscopy images together with roughness values of TiO_2/Al_2O_3 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 TiO_2 and prior reports.