Jin-Cherng HSU¹, Paul W. WANG², Yung-Hsin LIN^3*, Huang-Lu CHEN³, Yu-Yun CHEN³, Yeong-Der YAO³, and Jen-Chieh YU³

¹Department of Physics, Fu Jen Catholic University, 510 Chung-Cheng Rd., Hsinchuang, Taipei Hsien 24205, Taiwan
²Department of Physics, Bradley University, 1501 W. Bradley Ave., Peoria, IL 61625, U.S.A.
³Graduate Institute of Applied Science and Engineering, Fu Jen Catholic University, 510 Chung-Cheng Rd., Hsinchuang, Taipei Hsien 24205, Taiwan

(Received April 29, 2010; Accepted September 8, 2010)

The surface of poly(methyl methacrylate) (PMMA) was treated by plasma with an end-Hall ion source in vacuum in order to enhance its anti-reflectivity. The cone-shaped bumps induced by the plasma etching have shown an anti-reflective effect. Moreover, PMMA has poor thermal durability due to its low melting point; therefore, the etched PMMA was further coated by a 5 nm thick SiO₂ film after 900 and 1300 s plasma etching. Samples after SiO₂ coating were thermally annealed at temperature of 70 °C for 1 h. Experiments show that transmittance was increased after 5 nm thick SiO₂ coating. The of transmittance of PMMA after both sides treated by 900 s plasma etching and 5 nm SiO₂ coating was not changed after thermal annealing. However, without SiO₂ coating the transmission was reduced 1% after annealing. Atomic force microscope (AFM) demonstrated that the nano-structures of cone-shaped bumps were formed on the PMMA after plasma etching and a smoother nano-structured pattern preserved the transmittance of the PMMA after both sides treated by 900 s plasma etching and 5 nm SiO₂ coating. Three dimensional photonic crystal formed by uniformly distributed cone-shaped bumps was assumed to result in the reduction of the anti-reflectivity of treated PMMA.

Key words: poly(methyl methacrylate) (PMMA), anti-reflectivity, plasma etching, thermal stability of transmittance

^*E-mail address: 496598033@mail.fju.edu.tw