Abstract
$Al_2O_3$ thin films were deposited on the moth eye anti-reflective nanostructured polycarbonate films by atomic layer deposition (ALD) techniques. Without ALD-$Al_2O_3$ thin films, moth eye anti-reflective nanostructured films had a high optical transmittance of 95.47% at a wavelength of 550 nm and a very poor hardness of 0.1381 GPa. With increasing the thickness of $Al_2O_3$ thin films from 5 to 25 nm, the transmittance of moth eye anti-reflective nanostructured films was gradually decreased from 94.94 to 93.12%. On the other hand, the hardness of the films was greatly increased from 0.3498 to 0.7806 GPa with increasing the thickness of $Al_2O_3$ thin films. This result shows that ALD thin films can be applied to improve mechanical properties with an adequate optical transmittance of the conventional moth eye anti-reflection nanostructure films.