WGP fabrication and modeling. (a) Diblock copolymer (circles: PS cylinders in PHMA matrix) atop amorphous Si layer on fused-silica substrate, where copolymer has periodicity and cylinder diameter . (b) Postetched system with amorphous Si wires atop fused-silica substrate. (c) Structure utilized in numerical model, where wires are idealized to possess a rectangular profile.
Comparison of polarization efficiencies of two devices, one (Ref. 4) fabricated from PS/PHMA 22/63 (, solid line) and one from PS/PHMA 47/145 (, dashed line). Polystyrene volume fraction for both polymers.
Refractive index () and extinction (absorption) coefficients () of α-Si for fabricated sample, as compared to literature values.12 For clarity every 5th data point is plotted for the Palik data and every 50th data point is plotted for our experimental data. See Table I in the supplementary material at Ref. 10 for a comprehensive table of values and Fig. 8 in Ref. 10 for a corresponding graphical presentation.
Representative model predictions showing the effect of varying (a) (, ), (b) (, ), and (c) (, ). Panel (a) also includes a prediction for the small- limit.
Summary plot showing the trend of polarization efficiency at vs both and for ; lines are best-fit curves. ◼ , ● , ▲ , ▼ , , , ◆ , and . derived from relationship which is defined by the experimental etch rate ratios and Eq. (3).
Experimental system fabricated from 47/145 PS/PHMA (dotted line) vs model prediction (solid line) with parameters , , and .
(a) AFM phase image: block copolymer, postshear, prestaining indicating long-range alignment of PS cylinders (white in image) in PHMA matrix; (b) AFM amplitude image: block copolymer, postshear, poststaining, indicating the wiggle introduced by buckling of the PS cylinders in the staining process; and (c) SEM image: finished WGP, showing projection of wiggle from mask into final wires. All images ; scale bar in (c) is .
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