Surface Nanostructures Formed by Phase Separation of Metal Salt–Polymer Nanocomposite Film for Anti-reflection and Super-hydrophobic Applications

• Main Authors: Celal Con, Bo Cui
• Format: Article
• Language: English
• Published: SpringerOpen 2017-12-01
• Series: Nanoscale Research Letters
• Subjects: Surface structures; Self-assembly; RIE; Metal salt; Anti-reflectivity; Super-hydrophobicity
• Online Access: http://link.springer.com/article/10.1186/s11671-017-2402-4

Abstract This paper describes a simple and low-cost fabrication method for multi-functional nanostructures with outstanding anti-reflective and super-hydrophobic properties. Our method employed phase separation of a metal salt–polymer nanocomposite film that leads to nanoisland formation after etching away the polymer matrix, and the metal salt island can then be utilized as a hard mask for dry etching the substrate or sublayer. Compared to many other methods for patterning metallic hard mask structures, such as the popular lift-off method, our approach involves only spin coating and thermal annealing, thus is more cost-efficient. Metal salts including aluminum nitrate nonahydrate (ANN) and chromium nitrate nonahydrate (CNN) can both be used, and high aspect ratio (1:30) and high-resolution (sub-50 nm) pillars etched into silicon can be achieved readily. With further control of the etching profile by adjusting the dry etching parameters, cone-like silicon structure with reflectivity in the visible region down to a remarkably low value of 2% was achieved. Lastly, by coating a hydrophobic surfactant layer, the pillar array demonstrated a super-hydrophobic property with an exceptionally high water contact angle of up to 165.7°.