title: Wafer-scale highly-transparent and superhydrophilic sapphires for high-performance optics.
abstract: We reported the wafer-scale highly-transparent and superhydrophilic sapphires with antireflective subwavelength structures (SWSs) which were fabricated by dry etching using thermally dewetted gold (Au) nanomasks. Their optical transmittance properties were experimentally and theoretically investigated. The density, size, and period of the thermally dewetted Au nanopatterns can be controlled by the Au film thickness. For the sapphire with both-side SWSs at 5 nm of Au film, the average total transmittance (T(avg)) of ~96.5% at 350-800 nm was obtained, indicating a higher value than those of the flat sapphire (T(avg)~85.6%) and the sapphire with one-side SWSs (T(avg)~91%), and the less angle-dependent transmittance property was observed. The calculated transmittance results also showed a similar tendency to the measured data. The SWSs enhanced significantly the surface hydrophilicity of sapphires, exhibiting a water contact angle (θ(c)) of < 5° for Au film of 5 nm compared to θ(c)~37° of the flat sapphire.
authors.affiliation: Department of Electronics and Radio Engineering, Institute for Laser Engineering, Kyung Hee University, Giheung-gu, Yongin-si, Gyeonggi-do, South Korea.
authors.forename: Jung Woo
authors.initials: JW
authors.lastname: Leem
authors.forename: Jae Su
authors.initials: JS
authors.lastname: Yu
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D004867:Equipment Design; D006046:Gold; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D049329:Nanostructures; D055095:Optics and Photonics / Q000295:instrumentation*; D012031:Refractometry / Q000295:instrumentation*; D013499:Surface Properties
chemical_list: D006046:Gold; D000537:Aluminum Oxide