Nanophase-Separated Polymer Films as High-Performance Antireflection Coatings

H. A. Macleod Thin-Film Optical Filters (Hilger Bristol UK 1986).

Minot M. J., J. Opt. Soc. Am. 66, 515 (1976).

Uhlmann D. R., Suratwala T., Davidson K., Boulton J. M., Teowee G., J. Non-Cryst. Solids 218, 113 (1997).

Heine C., Morf R. H., Appl. Opt. 34, 2476 (1995).

Wilson S. J., Hutley M. C., Opt. Acta 29, 993 (1982).

Walheim S., Böltau M., Mlynek J., Krausch G., Steiner U., Macromolecules 30, 4995 (1997).

Böltau M., Walheim S., Mlynek J., Krausch G., Steiner U., Nature 391, 877 (1998).

A patent application for this method was filed with the German Patent Office on 26 June 1998 under number 198 29 172.8.

Nanoporous films based on a PS-polyvinylchloride mixture show practically identical results (S. Walheim and U. Steiner unpublished material).

All polymers were purchased from Polymer Standards Service in Mainz and were used as obtained. Polymer polydispersities were 1.1 and lower. As solvents analytic grade THF [stabilized with 2.6-di- tert -butyl-4-methylphenol (250 mg/liter)] cyclohexane and ethanol were used. Standard microscope glass slides 1 mm thick were used as substrates.

Atomic force microscopy measurements were carried out on a self-built AFM. Layer thicknesses and refractive indices were measured with a single-wavelength (λ = 632.8 nm) ellipsometer (Riss Ellipsometerbau model EL X-1). For the ellipsometry measurements polished silicon wafers were used as substrates. Light transmission spectra were measured with a Perkin Elmers Lambda 40 spectrometer at vertical incidence with an open reference beam.

The film in Fig. 2A was cast from a THF solution (3% polymer by weight) of PS (M w = 94.4 kg/mol) and PMMA (M w = 100 kg/mol) (50:50% w/w). In Fig. 2B a mixture of PS (M w = 10.3 kg/mol) and PMMA (M w = 10.6 kg/mol) (70:30% w/w) in THF (2% polymer by weight) was used. In both cases the PS phase was removed by exposing the sample for 1 min to cyclohexane.

A ternary mixture of PS (M w = 10.3 kg/mol 60% by weight) PMMA 1 (M w = 10.6 kg/mol) and PMMA 2 (M w = 1.96 kg/mol) in THF (2% polymer by weight) was used. The as-cast films were exposed for 30 s to cyclohexane to remove the PS phase and subsequently for 10 s to ethanol which partially dissolves PMMA 2 .

A mixture of PS (M w = 1.92 kg/mol) PMMA (M w = 1.96 kg/mol) and a PS-PMMA diblock [M w = 54(PS)-54(PMMA) kg/mol] (57.5:37.5:5% w/w/w) in THF (2% polymer by weight) was used. The sample was exposed for 30 s to cyclohexane to remove the PS phase.

10.1126/science.278.5344.1795

Supported by the Deutsche Forschungsgesellschaft (DFG) (grant SFB 513 B2). U.S. acknowledges financial support by a research fellowship (Habilitations-Stipendum) of the DFG. We thank S. Eggert and T. P. Russell for useful discussions H.-J. Apell for the use of his spectrometer R. Adams for his help with the manuscript and R. Müller for his help with the experiments.