Holmium and titanium oxide nanolaminates by atomic layer deposition

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. - Highlights: • 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