Farbrication of submicron ZnO:Al gratings with wet etching and lift-off technology

With a photoresist pattern acquired by laser interference lithography as an etch mask, submicron aluminum-doped zinc oxide (AZO) gratings, which had excellent anti-reflection properties, were acquired by using wet etching and lift-off technology. The surface morphology was observed by an atomic force microscopy (AFM), and the reflectance spectrum was tested with a ultra-visible spectrophotometer. Results show that the AZO grating fabricated by wet etching is rougher than that acquired by lift-off technology, and the root mean squares of surface topographies of the two gratings are 25.4 nm and 7.6 nm, respectively. In the waveband range of 400-900 nm, two structural AZO gratings with the same period (980 nm) and height (160 nm) decrease the average total reflectance from 12.5% of the AZO thin film to 8.3% and 10.2%, respectively. The average specular reflectance are 6.2% and 6.6%, and diffuse reflectance are 2.1% and 3.6%, accordingly. It is concluded that wet etching-made AZO grating with rough surfaces decrease diffuse reflectance greatly, and are better in decreasing total reflectance than lift-off-made AZO grating with flatter surfaces.