Holmium and titanium oxide nanolaminates by atomic layer deposition

• Ho2O3–TiO2 nanolaminates were grown by atomic layer deposition.
• Ho2O3–TiO2 nanolaminates were crystallized at 700–800 deg.
• Ternary Ho2Ti2O7 was formed upon annealing.
• Annealed Ho2O3–TiO2 demonstrated soft magnetization hysteresis at room temperature.

Nanolaminate (nanomultilayer) thin films of TiO2 and Ho2O3 were grown on Si(001) substrates by atomic layer deposition at 300 °C from alkoxide and β-diketonate based metal precursors and ozone. Individual layer thicknesses were 2 nm for TiO2 and 4.5 nm for Ho2O3. As-deposited films were smooth and X-ray amorphous. After annealing at 800 °C and higher temperatures the nanolaminate structure was destroyed by solid-state reaction to form Ho2Ti2O7. The films demonstrated diamagnetic or paramagnetic behaviour in the as-deposited state. After annealing, the films possessed net magnetic moment, allowing one to record saturation magnetization and weak coercivity.