Broadband highly transparent sapphires with biomimetic antireflective compound submicrometer structures for optical and optoelectronic applications

• Published in: Journal of the Optical Society of America. B, Optical physics Optical physics, 2013-06, Vol.30 (6), p.1665-1670
• Main Authors: Leem, Jung Woo, Kim, Myung Sub, Yu, Jae Su
• Format: Article
• Language: English
• Subjects: Arrays; Broadband; Etching; Gold; Nanocomposites; Nanomaterials; Nanostructure; Sapphire
• ISSN: 0740-3224; 1520-8540
• DOI: 10.1364/JOSAB.30.001665

We reported the broadband highly transparent sapphires with biomimetic antireflective compound submicrometer structures (c-SMSs) made of disordered nanocone arrays on closely packed ordered hemispherical submicrometer gratings (o-SMGs). The o-SMGs and nanocones were fabricated using the spin-coated silica spheres and thermally dewetted gold (Au) nanoparticles, respectively, as the etch masks by a dry etching. The silica spheres with an average diameter of similar to 700 plus or minus 10 nm were synthesized. The dot-like Au nanoparticles were formed from the Au thin films with different thicknesses by a proper heat treatment. The total and diffuse transmission characteristics of the fabricated c-SMSs on sapphires were investigated at wavelengths of 350-1100 nm, together with theoretical predictions using a rigorous coupled wave analysis simulation. For the c-SMSs with taller and larger nanocone arrays at 7nmof Au film, an average total transrmttance (T sub(avg)) of similar to 90.7% was obtained, exhibiting haze ratios (H) of similar to 33.3 and 26% at lambda = 525 and 635 nm, respectively. These values were much higher than those of bare sapphire (i.e., T sub(avg) similar to 85.4%, H similar to 5.4 and 3.7% at lambda = 525 and 635 nm, respectively). The surface of fabricated c-SMSs also exhibited a strong hydrophilic property with a low water contact angle of similar to 10 degree .