Facile fabrication and optical characterization of nanoflake aluminum oxide film with high broadband and omnidirectional transmittance enhancement

In this study, the non-lithography fabrication of nanoflake aluminum oxide (Al2O3) film with omnidirectional broadband antireflection properties was demonstrated. The nanoflake Al2O3 films on glass slide and silicon wafer substrates were sequentially prepared by reactive magnetron sputtering and surface modification with alkali-treatment and hot water treatment processes. The morphologies, chemical compositions and optical properties of the prepared samples were characterized by field-emission scanning electron microscope (FE-SEM), photoelectron spectroscopy (PES), variable angle spectroscopic ellipsometry (VASE) and UV-VIS spectrophotometry with angle-dependent transmittance measurements, respectively. The results indicated that the thickness of the sputtered Al2O3 film was a crucial parameter for the growth of nanoflake for the nanostructure formed by alkali treatment with 0.1 M of potassium hydroxide (KOH) at room temperature and hot water treatment in deionized (DI) water at 80 °C for 3 min. The best optical performance was achieved with the single nanoflake film layer, resulting in enhanced optical transmittance exceeding 90% over the broad range of visible region at wide incident angle. This facile fabrication process of the nanoflake layer was offering the potential benefits for inexpensive omnidirectional anti-reflection (AR) coating in large area.