Laser-induced large area sub-μm and nanostructuring of dielectric surfaces and thin metal layer

The sub-um- and nanostructured thin metal layers and dielectric surfaces exhibit manifold applications. However, the fast, easy and cost-effective fabrication is still a challenge. A possible technological solution is laser-induced self-organized processes like IPSM-LIFE (laser-induced front side etching using in-situ pre-structured metal layer). At IPSM-LIFE, a metal covered dielectric is irradiated where self-organized molten metal layer deformation process assists the structuring. A chromium-fused silica system was irradiated by a KrF excimer laser (lambda = 248 nm, Delta t(p) = 25 ns, f = 100 Hz). The IPSM-LIFE can be divided into two steps: STEP 1 and STEP 2. At IPSM - LIFE STEP 1: The laser irradiation of thin metal layers on dielectric surfaces results in a melting and consequently in a nanostructuring process of the metal layer. The laser treatment induced a large-area modification of the sample surface. These modifications allow a macroscopic adjustment of the optical properties as well as of the water contact angle. The transmission can be variated from similar to 3 % to similar to 74 % for visible light and the water contact angle from < 5 degrees to similar to 97 degrees. The localized modification of the optical properties allows the fabrication of high-resolution greyscale images. Furthermore, the pre-structured metal layer can be used as a mask for a reactive ion beam etching (RIBE) of the SiO2. The RIBE process allows the fabrication of sub-um glass structures with a diameter down to 30 nm and a high aspect ratio (> 10) at the same time. At IPSM-LIFE - STEP 2: A subsequent high laser fluence treatment of the pre-structured metal layer results in a structuring of the underlying dielectric surface. The RIBE and IPSM-LIFE structured fused silica surface exhibits water contact angle up to 105 degrees. The resultant surface topography was analyzed by optical (OM), atomic force (AFM) and scanning electron microscopy (SEM).