Superdark and Superhydrophobicity properties of two-tier silicon nanostructure

• Main Authors: Yan-Chen Chen, 陳諺辰
• Other Authors: Senfar Wen
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/41814121851231573375

碩士 === 中華大學 === 電機工程學系(所) === 97 === This paper provides an easy and high-efficient plasma etching technique which can produce the tapered structure, nanograss ,which have even height and diameter on (100) Si wafer. By using this method, we successfully produce the structure of nanograss with 380 nm height and the is 20 nm diameter at the bottom. The reflectivity between 190 nm and 1000 nm is smaller than 2%. Besides, we also use e-beam lithography to produce the 150 nm-diameter nanopillar with regular array. As these nanopillars were etched with nanograss structure on the top, they were characterized with reflectivity down to 1.2%. In addition, we used CHF3 plasma to decrease the surface energy to make the surface structure superhydrophobic. In general, as a liquid droplet sits on a composite solid-liquid-vapor interface, trapped air underneath the droplet is conducive to lift droplet, but increasing air fraction is harmful to the sitting stability. Here we used plasma and e-beam successfully to produce the air-like compound structure. The nanograss provides large contact angle, the nanopillar provides slippage, and the combination of both provides stability of superhydrophobicity. When air fraction was increased to 99.98% by increasing space between nanopillars, the water contact angle was up to 173º, and the sliding angle was close to 0º. Moreover, it can sustain the static pressure of 234 Pa, without losing the behavior of near-perfect superhydrophobicity.