Fabrication of Si-based two-dimensional photonic quasicrystals by using multiple-exposure holographic lithography
(Color online) Schematic diagram of Lloyd’s mirror setup and -rotation stages for multiple-exposure holography.
(Color online) Sequence of the main experiment steps for the fabrication of 2D PQCs: (a) PR layer was prepared on the top of a Cr (50 nm) and a Si wafer, (b) PR was patterned by using MHL and was developed, (c) Cr layer was wet etched, (d) RIE of Si was performed, and (e) the residual Cr was removed.
(Color online) Exposure process for fabrication of eightfold PQC pattern with rotation angles of (a) 0°, (b) 45°, (c) 90°, and (d) 135°.
Filling factors with the standard amount exposure at 16 at the center point as a function of the threshold exposure levels of (a) 4.5, (b) 5.0, (c) 5.5, (d) 6.0, (e) 6.5, (f) 7.5, (g) 8.0, (h) 9.0, (i) 10.0, (j) 11.0, (k) 12.0, and (l) 13.0, respectively.
SEM images of the developed eightfold PQC pattern fabricated by four exposures (, 45°, 90°, and 135°) with the step durations of (a) 1 s, (b) 1.5 s, and (c) 2 s.
SEM images of tenfold rotational symmetry PQC pattern fabricated by five exposures (, 36°, 72°, 108°, and 144°) and tenfold rotational symmetry PQC pattern fabricated by six exposures (, 30°, 60°, 90°, 120°, and 150°).
(Color online) Diffraction patterns produced by 632.8 nm HeNe laser beam at normal incidence onto the fabricated eight-, ten-, and 12-fold PQC patterns.
(Color online) SEM images of eightfold PQC pattern etched into a silicon wafer by using RIE.
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