Density-modulated alumina-based nanometre films prepared by sol–gel technique

Alumina-based nanometre films produced by a sol–gel method are investigated by wide-angle X-ray scattering and X-ray reflectometry. Every dipping cycle of the sol–gel route results in formation of an X-ray amorphous film exhibiting a density gradient. Both withdrawal speed and drying temperature used as tuning parameters during coating preparation influence the thickness and density of the sol–gel film. An increase of the withdrawal speed results in a thicker film of a lower mean density. An opposite effect is observed with an increase of the drying temperature. The appearance of multilayer Bragg reflections in the reflectivity curves of successive stacked films is discussed in detail. The thermal stability of the density-modulated aluminium oxide-based nanometre multilayers is investigated in a temperature range of 300–1000 °C. Possible applications as X-ray optical elements are outlined. PACS  61.10.Kw; 68.60.Dv; 81.20.Fw