Nanolaminated Al2O3-TiO2 thin films grown by atomic layer deposition

Alternately stacked Al2O3-TiO2 nanolaminates were grown by atomic layer deposition (ALD) using the precursors of trimethyl aluminum, tetraisopropyl titanium, and water at growth temperature of 250 °C. Laminated configuration and nanostructural features were analyzed by cross-sectional transmission electron microscopy (TEM), depth-profiling Auger electron spectroscopy (AES) and X-ray diffraction (XRD). These material characterizations were well interpreted with layer-by-layer ALD growth mode and material properties of single oxide films, namely conformal growth of amorphous Al2O3 with a growth rate of 1.0 Å/cycle and polycrystalline anatase TiO2 with 0.3 Å/cycle. In addition, the dependences of leakage current density on applied electric field were measured for several nanolaminates with different TiO2 content and bilayer, single Al2O3 and TiO2 layer, thickness. Obtained results exhibit the successful tailoring of leakage current densities and permittivity with adjusting layer thicknesses in the nanolaminates. These properties were discussed in terms of utility as a current-controlling layer in direct current thin-film electroluminescence (TFEL) devices.