Six-fold hexagonal symmetric nanostructures with various periodic shapes on GaAs substrates for efficient antireflection and hydrophobic properties

• Published in: Nanotechnology 2011-12, Vol.22 (48), p.485304-1-8
• Main Authors: Leem, Jung Woo, Song, Young Min, Yu, Jae Su
• Format: Article
• Language: English
• Subjects: Azo; Gallium arsenide; Gallium arsenides; Nanocomposites; Nanomaterials; Nanorods; Nanostructure; Reflectance
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/22/48/485304

We fabricated various periodic nanostructures with a six-fold hexagonal symmetry on gallium arsenide (GaAs) substrates using simple process steps, together with a theoretical analysis of their antireflective properties. Elliptical photoresist (PR) nanopillars, which are inevitably generated by the asymmetric intensity distribution of the laser interference, were converted to rounded lens-like patterns by a thermal reflow process without any additional complex optic systems, thus leading to an exact six-fold hexagonal symmetry. Various shaped periodic nanostructures including nanorods, cones, truncated cones, and even parabolic patterns were obtained under different etching conditions using the rounded lens-like PR patterns formed by the reflow process. For the parabolic structure, the calculated lowest average reflectance of ∼ 2.3% was obtained. To achieve better antireflection characteristics, an aluminum-doped zinc oxide (AZO) film was deposited on the GaAs parabolas, which forms an AZO/GaAs parabolic nanostructure. The structure exhibited a low average reflectance of ∼ 1.2% over a wide wavelength region of 350-1800 nm and a hydrophobic surface with a water contact angle of θ(c) ∼ 115°. The calculated reflectances were reasonably consistent with the measured results.