Nanopattern formation in UV laser treated a-AlOx and nc-Al/AlOx layers

• DC and RF sputtered AlOx surfaces had been treated by a single UV laser pulse.
• Focusing effect of silica nanospheres of the Langmuir–Blodgett film was confirmed.
• Ordered pit, or ordered hillock and crater patterns of 200 nm size were fabricated.
• Preparing nanostructures with periods below 100 nm is possible with this technique.
• The method enables the direct patterning of various materials.

Hexagonal nanopatterns were fabricated in sputter deposited Al-oxide thin films by means of single UV laser pulses via a layer of self-assembled silica nanospheres. The hexagonal pattern was projected to the surface due to the focussing effect of the silica nanolenses enhancing the local impact of the pulse. As a result of the laser pulse large area ordered structure of nano-pits were formed in RF (radio frequency) sputtered amorphous Al-oxide films, while nano-craters were created in DC (direct current) sputter deposited layers that consist of Al nanocrystals embedded in amorphous matrix. The two different mechanisms governing the nanostructure formation in the a-AlOx and nc-Al/AlOx composite layers were revealed by Atomic Force Microscopy (AFM), cross-sectional Transmission Electron Microscopy (XTEM), spectroscopic ellipsometry and computer simulation.